B cells are mediators of the humoral response, or antibody-mediated immunity. Studying this particular cell group can reveal the inner workings of the immune system, illuminating the possible causes behind various immune disorders and cancers.

B cell subtypes are identified by their surface markers, which are analyzed using flow cytometry and cell analysis techniques.

B-cell generation begins in the bone marrow, where hematopoietic stem cells give rise to common lymphoid progenitor cells, which differentiate into B lineage cells. Before birth, the fetal liver is the primary site of B cell development. Throughout each stage of development, the antibody locus – a site where an antigen interacts with the cell undergoes genetic recombination specific to the developmental stage of the B cell. Development starts with the pro-B cell, which develops further into the pre-B cell. Maturation in the bone marrow ends with the naïve B cell that expresses the B cell receptor capable of recognizing an antigen. These cells then leave the bone marrow and enter the periphery. Peripheral human B cells and peripheral blood lymphocytes are present in the peripheral blood and tissues such as the human spleen and lymph node.

Learn more about B-cell generation with our downloadable poster.

During B cell maturation, cells differentiate into mature B cells and various cell subsets, including naïve B cells, memory B cells, and activated B cells, each with distinct expression patterns of cell surface markers.

Plasma B cells:  A plasma cell is the sentry of the immune system. The naïve B cell circulates throughout the body. When it encounters a unique antigen, the plasma cell takes in the antigen through receptor-mediated endocytosis. Antigenic particles are transferred to the cell surface, loaded onto MHC II molecules, and presented to a helper T cell. The binding of the helper T cell to the MHC II-antigen complex activates the B cell. The activated B cell goes through a period of rapid proliferation and somatic hypermutation. Selection occurs for those cells that produce antibodies with a high affinity for that particular antigen. Once terminally differentiated, the plasma B cell only secretes antibodies specific for that antigen and can no longer generate antibodies to other antigens. Antibody-secreting cells, including short-lived plasma cells, play a key role in the secondary immune response by rapidly producing large amounts of antibodies.

Memory B cells:  Memory cells are held in reserve, in the germinal centers of the lymphatic system, for when the immune system re-encounters a specific antigen. During any repeat exposure, the follicular helper T cell causes the memory cell to differentiate into a plasma B cell with greater sensitivity to that specific antigen. This jump-starts the immune system to mount a quicker, more powerful response than was possible previously. T cell-dependent activation is crucial for forming memory B cell subsets, which mediate a rapid secondary immune response.

B-1 cells:  a minor subtype, only about 5% in humans, of self-renewing fetal B cells that act similarly to plasma cells. B-1 cells are primarily present during fetal and neonatal life.

Marginal zone (MZ) B cells:  Marginal zone B cells and marginal zone B are specialized cell subtypes found in the marginal zone of the human spleen and lymphoid follicles. These mature memory B cells can be activated through toll-like receptor ligation and not necessarily through the B cell receptor.

Follicular (FO) B cells:  These are mature, but inactive, B cells. This subset of B cells is primarily found in the follicles of the spleen and lymph nodes. Activation of these cells requires the aid of T cells. FO B cells can differentiate into either plasma or memory B cells.

Regulatory B (Breg) cells: Breg cells negatively regulate the strength of the immune response and inflammation by secreting chemical messages called cytokines, such as IL-10. Regulatory B cells, other regulatory cells, and secreted cytokines secrete anti-inflammatory cytokines, which modulate T cell responses. Although these cells comprise a small portion of the B cell population (~0.5% in humans), it is thought that loss of functional Breg cells contributes to autoimmune disorders.

Understanding B cell lineage, B cell compartments, and B cell populations requires knowledge of cell biology, cell differentiation, and the role of transcription factors. Cell marker panels and cell surface markers are used to distinguish B-cell subsets and cell subtypes in both human and mouse B cells. During flow cytometry analysis, dead cell exclusion is essential for accurately identifying B cell subsets. The diversity of B-cell receptors helps define cell lineage and functional specialization. Analyzing expression patterns and cytokine production in different B cell compartments is important for understanding immune function.

Mature B cells are a key component of the adaptive immune system, responsible for antigen recognition and antibody production. These cells express a distinct set of surface markers that help define their identity and function. Immunoglobulin M (IgM) is commonly found on the surface of mature B cells, indicating their readiness to respond to antigens. HLA-DR, a major histocompatibility complex class II molecule, supports antigen presentation to T cells.

CD19 and CD20 are widely used markers for identifying B cells in flow cytometry and immunohistochemistry. CD19 is involved in B cell receptor signaling, while CD20 plays a role in calcium transport and cell activation. CD40 is another important marker that facilitates interactions with T helper cells, promoting B cell survival and differentiation. These markers help researchers study B cell development, immune responses, and therapeutic targets in autoimmune diseases and B cell malignancies.

IgM

Immunoglobulin M (IgM) is a surface-bound antibody that marks the early functional stage of mature B cells. It is the first immunoglobulin expressed during B cell development and plays a role in initial antigen recognition. Surface IgM enables B cells to bind antigens and initiate signaling cascades. Researchers use IgM expression to identify naïve and mature B cells in immunophenotyping, helping to study immune responses, B cell maturation, and antibody production in health and disease.

Figure 1. Immunocytochemistry/ Immunofluorescence - Anti-Human IgM antibody [EPR20731] (ab212201).

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HLA-DR

HLA-DR is a major histocompatibility complex class II molecule expressed on the surface of mature B cells. It plays a role in presenting processed antigens to CD4⁺ T cells, facilitating adaptive immune responses. HLA-DR expression is used to identify antigen-presenting cells, including B cells, in immunophenotyping. Its presence reflects the functional readiness of B cells to interact with T cells, making it a valuable marker in studies of immune activation, autoimmunity, and vaccine responses.

Figure 2. Flow Cytometry - Anti-HLA-DR antibody [TAL 1B5] (ab20181).

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CD19

CD19 is a transmembrane protein expressed throughout most stages of B cell development, including mature B cells. It functions as a co-receptor that enhances B cell receptor (BCR) signaling, supporting activation and proliferation. CD19 is widely used in flow cytometry to identify B cells and monitor immune responses. Its consistent expression on mature B cells makes it a valuable marker in research and clinical settings, including studies of immunodeficiencies, autoimmune diseases, and B cell-targeted therapies.

Figure 3. Multiplex immunohistochemistry - Anti-CD19 antibody [EPR23174-145] - BSA and Azide free (ab267394).

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CD20

CD20 is a membrane-spanning protein expressed on the surface of mature B cells, from the pre-B cell stage through to memory B cells. It is involved in calcium signaling and B cell activation, although its exact function remains under investigation. CD20 is widely used as a marker in flow cytometry and is a target in monoclonal antibody therapies for B cell malignancies. Its stable expression makes it a reliable indicator of mature B cell populations.

Figure 4. Flow Cytometry (Intracellular) - Anti-CD20 antibody [EP459Y] (ab78237).

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CD40

CD40 is a transmembrane protein expressed on mature B cells, playing a role in immune regulation and cell signaling. It interacts with CD40L on T cells, supporting B cell activation, proliferation and antibody production. CD40 expression helps distinguish mature B cells from earlier developmental stages, making it a useful marker in immunophenotyping and research. Its involvement in immune responses also makes it a focus in studies on autoimmune diseases and targeted immunotherapies.

Figure 5. Flow Cytometry - Anti-CD40 antibody [EPR20735] (ab224639).

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Activated B cells play a role in adaptive immunity and can be identified by specific surface markers. IgM is one of the earliest antibodies expressed, indicating recent activation and involvement in primary immune responses. CD19 is a consistent marker found on most B cells, supporting signal transduction and cell development. CD30 is less commonly expressed but appears in certain activated B cell subsets, particularly in inflammatory or disease-related environments.

These markers help researchers track B cell activation, study immune dynamics, and explore disease mechanisms. Their expression patterns are useful in immunophenotyping, diagnostics, and therapeutic development. Understanding how these markers behave in different contexts supports ongoing research in immunology, oncology, and autoimmune disorders. By combining marker analysis with functional assays, scientists can gain deeper insights into B cell biology and immune regulation.

IgM

Immunoglobulin M (IgM) is one of the first antibodies produced during an immune response and is commonly used as a marker of activated B cells. Its surface expression indicates early activation and differentiation, particularly in response to antigen exposure. IgM plays a role in pathogen neutralization and complement activation. Researchers often use IgM levels to study B cell function, immune status and disease progression in both experimental and clinical immunology settings.

Figure 6. Flow Cytometry - Anti-Human IgM antibody [EPR20731] (ab212201).

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CD19

CD19 is a transmembrane protein expressed throughout most stages of B cell development, including activation. It supports signal transduction and enhances B cell receptor responses. In activated B cells, CD19 works alongside other markers like IgM and CD30 to indicate immune engagement and functional status. Its consistent expression makes it a valuable tool in immunophenotyping, disease monitoring and therapeutic research. CD19 is widely used in studies exploring B cell biology, immune regulation and targeted immunotherapies.

Figure 7. Immunocytochemistry/ Immunofluorescence - Anti-CD19 antibody [EPR5906] (ab134114).

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CD30

CD30 is a surface receptor expressed on a subset of activated B cells, particularly under conditions of immune stimulation or disease. It belongs to the tumor necrosis factor receptor family and is often associated with cell signaling and regulation. CD30 expression can help identify activated B cells in specific contexts, including autoimmune responses and certain lymphomas. Researchers use CD30 alongside markers like CD19 and IgM to study immune activation, disease progression and therapeutic response.

Figure 8. Flow Cytometry - Anti-CD30 antibody [EPR24238-228] (ab271127).

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Plasma cells are terminally differentiated B cells that specialize in antibody secretion. They can be identified through a combination of surface and intracellular markers. CD38 and CD138 are commonly used to define plasma cells in both research and clinical settings. IgG is often produced in large quantities, reflecting the cell’s antibody-secreting function. CD45 expression is typically reduced, helping distinguish plasma cells from earlier B cell stages. CD184 (CXCR4) guides plasma cell migration to bone marrow niches. TNFRSF17 (BCMA) supports plasma cell survival and is a target in therapeutic development.

These markers are used in flow cytometry, immunohistochemistry, and molecular profiling to study immune responses, plasma cell disorders, and treatment outcomes. Understanding their expression patterns helps researchers explore antibody production, immune regulation, and disease progression in both health and pathology.

CD38

CD38 is a transmembrane glycoprotein commonly used to identify plasma cells, the antibody-secreting stage of B cell development. It is highly expressed on plasma cells and plays a role in cell adhesion, signal transduction and calcium signaling. CD38 is often used in combination with markers like CD138 to distinguish plasma cells from other lymphocyte populations. Its expression is also relevant in studies of multiple myeloma, autoimmune conditions and immune response profiling.

Figure 9. Immunohistochemistry (Formalin/PFA-fixed paraffin-embedded sections) - Anti-CD38 antibody [EPR4106] (ab108403).

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CD138

CD138, also known as syndecan-1, is a surface proteoglycan widely used to identify plasma cells. It plays a role in cell adhesion and interaction with the extracellular matrix. CD138 is typically expressed at high levels on mature plasma cells and is often used in combination with CD38 for immunophenotyping. Its expression helps distinguish plasma cells from other B cell stages and is valuable in research on antibody production, multiple myeloma, and immune system regulation.

Figure 10. Flow Cytometry - Anti-Syndecan-1 antibody [B-A38] (ab34164).

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IgG

IgG is a major immunoglobulin produced by plasma cells during adaptive immune responses. Its presence reflects the antibody-secreting function of mature B cells. High levels of IgG are typically associated with long-lived plasma cells and sustained immunity. In research and diagnostics, IgG expression helps identify functional plasma cells and monitor immune activity. It is often used alongside markers like CD38 and CD138 to study antibody production, vaccine responses and plasma cell–related disorders.

Figure 11. Immunohistochemistry (Formalin/PFA-fixed paraffin-embedded sections) - Anti-Human IgG antibody [IG266] (ab200699).

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CD45

CD45 is a protein tyrosine phosphatase expressed on most hematopoietic cells, including B cells. During plasma cell differentiation, CD45 expression is typically reduced or absent, making it a useful marker for distinguishing mature plasma cells from earlier B cell stages. This downregulation helps researchers identify plasma cells in flow cytometry and tissue analysis. CD45 is often evaluated alongside markers like CD38 and CD138 to study immune responses, plasma cell disorders, and therapeutic outcomes.

Figure 12. Flow Cytometry - Anti-CD45 antibody [EPR27167-58] (ab303670).

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CD184

CD184, also known as CXCR4, is a chemokine receptor involved in plasma cell migration and homing to bone marrow niches. Its expression increases as B cells differentiate into plasma cells, guiding their movement in response to CXCL12. CD184 is often used alongside markers like CD38 and CD138 to identify mature plasma cells in immunological studies. It plays a role in understanding immune responses, plasma cell survival, and the microenvironment in both health and disease.

Figure 13. Immunocytochemistry/ Immunofluorescence - Anti-CXCR4 antibody [EPUMBR3] (ab181020).

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TNFRSF17

TNFRSF17, also known as BCMA, is a receptor expressed predominantly on plasma cells. It binds to ligands such as APRIL and BAFF, supporting plasma cell survival and function. TNFRSF17 is frequently used in combination with markers like CD38 and CD138 to identify mature plasma cells in both research and clinical settings. Its expression is also relevant in studies of multiple myeloma and targeted therapies, making it a valuable marker in immunology and oncology research.

Figure 14. Flow Cytometry - Anti-BCMA antibody [EPR22457-260] (ab253242).

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Memory B cells are long-lived components of the adaptive immune system that respond rapidly upon re-exposure to antigens. CD19 and CD20 are broadly expressed on B cells, including memory subsets. CD21 supports antigen recognition and co-stimulation. CD27 is a hallmark of memory B cells, distinguishing them from naïve populations. CD69 is an early activation marker that may appear on tissue-resident memory B cells. CD95 (Fas) is involved in apoptosis regulation and is often upregulated in activated memory cells. These markers are used in flow cytometry and immunophenotyping to study immune memory, vaccine responses, and autoimmune conditions. Understanding their expression patterns helps researchers explore B-cell differentiation, survival, and function across various immunological contexts.

CD19

CD19 is a transmembrane protein expressed throughout most stages of B cell development, including memory B cells. It plays a role in signal transduction and helps regulate B cell activation and differentiation. In memory B cells, CD19 remains consistently expressed, making it a reliable marker for identification and tracking. Researchers often use CD19 in combination with markers like CD27 and CD20 to study immune memory, vaccine responses and B cell–mediated conditions in both health and disease.

Figure 15. Flow Cytometry - Anti-CD19 antibody [EPR23174-145] (ab245235).

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CD20

CD20 is a membrane-embedded protein expressed on most mature B cells, including memory B cells. It plays a role in calcium signaling and B-cell activation. CD20 is commonly used in immunophenotyping to distinguish memory B cells from plasma cells, which typically lack CD20 expression. Its stable presence on memory B cells makes it a valuable marker in studies of immune memory, autoimmune conditions, and B cell–targeted therapies in both research and clinical applications.

Figure 16. Flow Cytometry (Intracellular) - Anti-CD20 antibody [EP459Y] (ab78237).

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CD21

CD21, or complement receptor 2, is expressed on mature and memory B cells. It plays a role in enhancing B cell activation by binding complement-coated antigens. In memory B cells, CD21 expression supports antigen recognition and immune recall. It is often used alongside markers like CD19 and CD27 to identify memory subsets in immunophenotyping. CD21 is also studied in the context of immune regulation, chronic infections, and autoimmune conditions.

Figure 17. Flow Cytometry - Anti-CD21 antibody [EPR27369-9] (ab315160).

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CD27

CD27 is a member of the tumor necrosis factor receptor family and is widely recognized as a marker of memory B cells. It helps distinguish memory B cells from naïve B cells, which typically lack CD27 expression. CD27 contributes to B cell activation and survival through interactions with its ligand, CD70. Researchers use CD27 with markers like CD19 and CD20 to study immune memory, vaccine responses, and B–cell–mediated immune regulation.

Figure 18. Immunocytochemistry/ Immunofluorescence - Anti-CD27 antibody [EPR8569] (ab131254).

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CD69

CD69 is an early activation marker expressed on various immune cells, including memory B cells. It is often associated with tissue-resident memory B cells and plays a role in cell retention within lymphoid and non-lymphoid tissues. CD69 expression can indicate recent activation or long-term residency in specific microenvironments. Researchers use CD69 alongside markers like CD27 and CD19 to study memory B cell subsets, immune surveillance, and localized immune responses in both health and disease.

Figure 19. Flow Cytometry - Anti-CD69 antibody [EPR25398-81] (ab307081).

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CD95

CD95, also known as Fas, is a cell surface receptor involved in regulating apoptosis. In memory B cells, CD95 expression is often elevated, reflecting their activation history and readiness for immune regulation. It plays a role in maintaining immune balance by controlling cell survival. CD95 is used alongside markers like CD27 and CD19 to identify activated memory B cell subsets and study immune responses, tolerance mechanisms, and autoimmune disease progression.

Figure 20. Flow Cytometry - Anti-Fas antibody [EPR27359-51] (ab307591).

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HLA-I

Human leukocyte antigen class I (HLA-I) molecules are widely known for presenting intracellular peptides to cytotoxic T cells. Recent studies suggest they may also serve as markers for identifying subsets of memory B cells. These long-lived cells are key players in adaptive immunity, capable of rapid response upon antigen re-exposure. HLA-I expression patterns can help distinguish memory B cells from naïve or activated B cells, offering insights into immune history and vaccine responses. Understanding how HLA-I contributes to memory B cell identification may support research in immunology, infectious disease, and therapeutic development.

Figure 21. Immunohistochemistry (Formalin/PFA-fixed paraffin-embedded sections) - Anti-MHC class I + HLA A + HLA B antibody [EPR1394Y] (ab134189).

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B-1 cells are a distinct subset of B lymphocytes involved in innate-like immune responses. They are primarily found in the peritoneal and pleural cavities and are known for producing natural antibodies. B-1 cells express CD19, a pan-B cell marker that supports signaling and development. High surface IgM levels reflect their role in early immune defense. CD1d, a lipid-presenting molecule, is also expressed and contributes to interactions with natural killer T cells. CD43 is another marker that helps distinguish B-1 cells from conventional B-2 cells, particularly in flow cytometry.

These markers are used to identify B-1 cells in immunological studies and to explore their roles in autoimmunity, infection, and tissue homeostasis. Understanding B-1 cell marker expression supports research into their unique functions and contributions to immune regulation.

IgM

IgM is a surface immunoglobulin highly expressed on B-1 cells, a unique subset of B lymphocytes involved in early immune defense. It plays a role in recognizing common microbial antigens and producing natural antibodies. High IgM expression helps distinguish B-1 cells from conventional B-2 cells. Researchers use IgM alongside markers like CD19, CD1d and CD43 to identify B-1 cells in immunological studies focused on innate-like immunity, autoimmunity and mucosal immune responses.

Figure 22. Flow Cytometry - Anti-Human IgM antibody [EPR20731] (ab212201).

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CD1d

CD1d is a non-classical MHC class I–like molecule expressed on B-1 cells and other immune cells. It presents lipid antigens to invariant natural killer T (iNKT) cells, linking innate and adaptive immunity. In B-1 cells, CD1d expression supports immune surveillance and regulatory functions. Researchers use CD1d alongside markers like CD19, IgM, and CD43 to identify B-1 cell populations and study their roles in mucosal immunity, inflammation, and immune tolerance.

Figure 23. Flow Cytometry - Anti-CD1d antibody [EPR22526-9] (ab256344).

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CD43

CD43 is a sialoglycoprotein expressed on various immune cells, including B-1 cells. It plays a role in cell adhesion, migration, and signaling. In B cell populations, CD43 expression helps distinguish B-1 cells from conventional B-2 cells, which typically lack this marker. Researchers use CD43 alongside markers like CD19, IgM, and CD1d to identify B-1 cells in flow cytometry and immunological studies focused on innate-like immunity, inflammation, and early antibody responses.

Figure 24. Immunocytochemistry/ Immunofluorescence - Anti-CD43 antibody [EPR21904] (ab235453).

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CD19

CD19 is a transmembrane protein expressed throughout B cell development and is widely used as a marker for B lineage cells. In particular, CD19 helps identify B-1 cells, a unique subset involved in innate-like immune responses. B-1 cells are primarily found in the peritoneal and pleural cavities and are known for producing natural IgM antibodies. Studies in CD19-deficient mice show a marked reduction in B-1 cell populations, suggesting CD19 supports their development and maintenance. Understanding CD19 expression in B-1 cells may inform research in autoimmunity, infection, and immunotherapy.

Figure 25. Flow Cytometry - Anti-CD19 antibody [BU12] (ab254170).

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CD197

CCR7 (CD197) is a chemokine receptor involved in guiding immune cells to lymphoid tissues. While commonly associated with T cell and dendritic cell migration, CCR7 expression has also been observed in subsets of B-1 cells. These innate-like B cells contribute to early immune responses and natural antibody production. CCR7 may influence their positioning within secondary lymphoid organs, supporting interactions with other immune cells. Its expression pattern can help distinguish B-1 cells from other B cell types, offering a potential marker for studying immune regulation and tissue-specific responses.

Figure. Flow Cytometry - Anti-CCR7 antibody [EPR29703-53] (ab324521).

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IgD

Immunoglobulin D (IgD) is a surface antibody co-expressed with IgM on mature B cells. While its function has long been debated, IgD is increasingly recognized for its role in modulating immune responses. In B-1 cells, which are known for producing natural antibodies and responding to common pathogens, IgD expression varies and may help distinguish functional subsets. Its presence influences antigen sensitivity and signaling thresholds, contributing to immune regulation. Studying IgD expression in B-1 cells may support efforts to better understand innate-like immunity and the balance between tolerance and activation.

Figure 27. Flow Cytometry - Anti-IgD antibody [IA6-2] (ab235125)

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Marginal zone B cells are a specialized subset of B lymphocytes located in the spleen’s marginal zone. They play a role in rapid antibody responses to blood-borne antigens. These cells are characterized by high surface expression of IgM, which supports early immune defense. CD21, a complement receptor, enhances antigen recognition and co-stimulation. CD23, a low-affinity IgE receptor, is expressed at lower levels compared to follicular B cells, helping distinguish marginal zone B cells in flow cytometry. This marker profile is used to identify and study marginal zone B cells in both human and murine models.

Researchers use these markers to explore immune responses, vaccine efficacy, and the development of B–cell–related disorders. Understanding marginal zone B cell markers contributes to broader insights into innate-like immunity and splenic architecture.

IgM

IgM is a surface immunoglobulin highly expressed on marginal zone B cells, a specialized subset located in the spleen. These cells respond quickly to blood-borne antigens and produce natural antibodies. High IgM expression helps distinguish marginal zone B cells from follicular B cells, which typically express more IgD. Researchers use IgM alongside markers like CD21 and CD23 to identify marginal zone B cells and study their roles in early immune responses and immune surveillance.

Figure 28. Immunocytochemistry/ Immunofluorescence - Anti-Human IgM antibody [EPR20731] - BSA and Azide free (ab228524).

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CD21

CD21 (complement receptor 2) is widely used to identify marginal zone B cells in the spleen. These cells typically express high levels of CD21 and low levels of CD23, distinguishing them from follicular B cells. CD21 plays a role in antigen capture and immune response modulation. Its expression pattern supports the classification of B cell subsets and contributes to studies on immune system organization, particularly in the context of innate-like B cell responses.

Figure 29. Flow Cytometry - Anti-CD21 antibody [EPR27369-9] (ab315160).

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CD23

CD23, a low-affinity IgE receptor, is commonly used to distinguish B cell subsets. Marginal zone B cells typically express low levels of CD23, in contrast to follicular B cells, which show higher expression. This differential expression helps define B cell populations in immunological studies. CD23 also participates in regulating B cell receptor signaling, influencing immune responses. Its expression profile supports its use as a marker in characterizing splenic B cell compartments and understanding adaptive immunity.

Figure 30. Flow Cytometry - Anti-CD23 antibody [SP23] (ab16702).

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IgD

Immunoglobulin D (IgD) is a surface antibody expressed on mature B cells, often alongside IgM. In marginal zone B cells, which reside in the spleen and respond quickly to blood-borne antigens, IgD expression is typically lower than in follicular B cells. This IgD^lowIgM^high profile helps distinguish MZ B cells from other B cell subsets. These cells play a role in early immune defense and are involved in T-independent responses. Monitoring IgD levels can support the identification and functional analysis of MZ B cells in both research and clinical settings.

Figure 31. Flow Cytometry - Anti-IgD antibody [11-26] - BSA and Azide free (ab235126).

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CD197

CD197, also known as CCR7, is a chemokine receptor involved in directing immune cells to lymphoid tissues. While typically associated with T cells and dendritic cells, CCR7 expression also plays a role in B cell positioning. In marginal zone B cells, low or absent CCR7 expression helps distinguish them from follicular B cells, which rely on CCR7 for migration into lymphoid follicles. This differential expression supports the identification of MZ B cells, which are specialized for rapid responses to blood-borne antigens. Studying CCR7 patterns may aid in understanding immune compartmentalization and B-cell function.

Figure. Flow Cytometry - Anti-CCR7 antibody [EPR29703-53] (ab324521).

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Follicular B cells are a key population within secondary lymphoid organs, involved in adaptive immune responses. The co-expression of IgD, CD19, and CD23 typically identifies these cells. IgD is a surface immunoglobulin that supports antigen recognition and B cell maturation. CD19 is a co-receptor that amplifies B cell receptor signaling, contributing to activation and differentiation. CD23, a low-affinity IgE receptor, is expressed at moderate levels and plays a regulatory role in B cell signaling and immune modulation. The combined expression of these markers helps distinguish follicular B cells from marginal zone and other B cell subsets.

This phenotypic profile is widely used in flow cytometry and immunological research to study B cell development, function, and response to antigens. Understanding these markers supports ongoing efforts to map immune cell diversity and refine therapeutic strategies targeting B cell-mediated conditions.

IgD

IgD is a surface immunoglobulin commonly expressed on mature follicular B cells. It plays a role in antigen recognition and helps define the naïve B cell compartment. Follicular B cells typically show high IgD and low IgM expression, distinguishing them from other B cell subsets. This marker is widely used in flow cytometry to identify B cell populations in lymphoid tissues. IgD expression supports studies on B cell development, immune response, and lymphoid tissue organization.

Figure 33. Flow Cytometry - Anti-IgD antibody [IA6-2] (ab235125).

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CD19

CD19 is a transmembrane protein expressed throughout B cell development and is widely used to identify follicular B cells. It acts as a co-receptor that enhances B cell receptor signaling, supporting antigen recognition and activation. In follicular B cells, CD19 expression is consistent and helps distinguish them from other lymphocyte populations. Its role in signal amplification makes it a valuable marker in immunophenotyping, particularly in studies focused on adaptive immunity and B-cell-mediated responses.

Figure 34. Flow Cytometry - Anti-CD19 antibody [6D5] (ab25232).

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CD23

CD23 is a low-affinity IgE receptor expressed on mature B cells, including follicular B cells. It plays a regulatory role in B cell receptor signaling and immune modulation. In follicular B cells, CD23 expression is typically moderate and helps distinguish them from marginal zone B cells. Studies suggest CD23 may influence antigen presentation and B cell activation by modulating receptor clustering and cytoskeletal dynamics, making it a useful marker in immunological profiling and B cell research.

Figure 35. Immunohistochemistry (Formalin/PFA-fixed paraffin-embedded sections) - Anti-CD23 antibody [EPR3617] (ab92495).

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IgM

Immunoglobulin M (IgM) is a surface antibody expressed during early B cell development and retained at varying levels in mature B cells. In follicular B cells, which circulate through lymphoid follicles and participate in T cell-dependent immune responses, IgM is typically expressed at moderate levels alongside high IgD. This IgM^low–midIgD^high profile helps distinguish follicular B cells from marginal zone B cells, which express higher IgM. Follicular B cells are involved in germinal center reactions and antibody affinity maturation. Tracking IgM expression supports the identification and functional analysis of follicular B cell subsets in immune research.

Figure 36. Flow Cytometry - Anti-Human IgM antibody [EPR20731] (ab212201).

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Regulatory B cells (Bregs) are a subset of B lymphocytes involved in immune tolerance and modulation. They are commonly identified by a combination of surface markers, including IgM, CD19, CD1d, CD21, and CD5. IgM and CD19 are broadly expressed on B cells and support antigen recognition and signaling. CD1d presents lipid antigens to invariant natural killer T cells, contributing to immune regulation. CD21 enhances B cell receptor signaling and antigen capture, while CD5 is associated with IL-10-producing Bregs and is often found on B1a cells. These markers help define Breg populations across different tissues and disease contexts.

Flow cytometry and immunological studies explore B cell-mediated suppression in autoimmunity, infection, and inflammation using their expression profiles. Understanding these markers supports efforts to characterize Breg function and their potential role in therapeutic strategies targeting immune dysregulation.

IgM

IgM is a surface and secreted immunoglobulin commonly expressed by regulatory B cells, particularly those with innate-like features. These cells maintain steady-state IgM levels and can rapidly produce natural IgM upon activation. IgM contributes to immune regulation by supporting IL-10 production and modulating early immune responses. Its expression is often used to identify B cell subsets with suppressive functions, including B1 and marginal zone B cells, which maintain immune homeostasis and tolerance.

Figure 37. Immunocytochemistry - Anti-Alpha Gal antibody [m86] - Human IgM (Chimeric) (ab281899).

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CD19

CD19 is a widely studied surface protein expressed throughout B cell development. It plays a role in identifying regulatory B cells (Bregs), which help modulate immune responses. CD19⁺ Bregs are often associated with IL-10 production and immune tolerance. Their presence has been observed in autoimmune conditions, cancer, and transplant models. Understanding CD19 expression patterns supports efforts to characterize Breg subsets and explore their therapeutic potential in immune modulation and disease management.

Figure 38. Flow Cytometry - Anti-CD19 antibody [BU12] (ab254170).

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CD1d

CD1d is a non-classical MHC class I-like molecule expressed on many B cell subsets. It presents lipid antigens to invariant natural killer T (iNKT) cells, supporting immune regulation. CD1d⁺ regulatory B cells (Bregs) can influence iNKT cell activity, contributing to the modulation of inflammatory responses. This interaction has been studied in autoimmune models, where CD1d expression on Bregs was linked to reduced disease severity. These findings highlight CD1d’s relevance in immune homeostasis and therapeutic research.

Figure 39. Flow Cytometry - PE Anti-CD1d antibody [1B1] (ab93508).

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CD21

CD21, also known as complement receptor 2, is expressed on mature B cells and plays a role in immune complex recognition. In regulatory B cells (Bregs), CD21 expression helps define subsets involved in immune tolerance. CD21⁻CD27⁻ B cells have been studied in autoimmune conditions like systemic lupus erythematosus, where their frequency may reflect disease activity. Exploring CD21 expression patterns supports efforts to understand better Breg phenotypes and their potential in immune-related research and therapies.

Figure 40. Immunocytochemistry/ Immunofluorescence - Anti-CD21 antibody [EP3093] (ab75985).

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CD5

CD5 is a surface glycoprotein expressed on a subset of B cells known as B1 cells. These CD5⁺ B cells are recognized for their role in immune regulation, particularly through IL-10 production. CD5 expression is linked to signaling pathways that influence B cell survival and cytokine release. In models of inflammation and tolerance, CD5⁺ regulatory B cells have been shown to interact with T cells, suggesting a role in modulating immune responses and maintaining homeostasis.

Figure 41. Flow Cytometry - Anti-CD5 antibody [EPR26532-12] (ab300144).

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IgD

Immunoglobulin D (IgD) is a surface antibody co-expressed with IgM on mature B cells. While traditionally linked to antigen recognition, recent studies suggest that IgD^low B cells may represent a distinct regulatory B cell subset. These cells have been shown to support immune tolerance by promoting regulatory T cell homeostasis and modulating inflammatory responses. Their phenotype and function differ from conventional B cells, offering a potential marker for identifying regulatory B cells in both mice and humans.

Figure 42. Flow Cytometry - Anti-IgD antibody [IA6-2] (ab235125).

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References

1. LeBien, T. W. & Tedder, T. F. B lymphocytes: how they develop and function. Blood 112, 1570–1580 (2008).
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