Monocyte and macrophage markers

Monocytes are a vital component of the immune system, originating from hematopoietic stem cells in the bone marrow. Once released into the bloodstream, these versatile immune cells circulate as human monocytes and can further differentiate into specialized cell types, including macrophages and dendritic cells. Monocytes are recognized for their ability to phagocytose pathogens and debris, as well as their role in orchestrating immune responses. Human monocytes are classified into three main subsets, classical monocytes, intermediate monocytes, and non-classical monocytes, each defined by distinct surface marker expression and functional characteristics. Understanding the biology and diversity of monocytes is essential for unraveling the complexities of the immune system and for advancing therapies targeting immune responses in health and disease.

Monocytes are differentiated from the myeloblasts in the bone marrow as part of the myeloid cell lineage. Blood monocytes consist of heterogeneous subpopulations with distinct phenotypic and functional properties. Post differentiation, a proportion of monocytes remains in the blood, and the rest randomly migrate into the tissue and body cavities. Blood monocytes and peripheral blood monocytes are key components of the immune system. This process is also known as leucocyte extravasation. The monocyte population is heterogeneous and can be classified based on cell surface markers and molecules. Classification of monocyte cell subpopulations utilizes gene expression profiling and the differential expression of cell surface receptors and chemokine receptors. Post extravasation, monocytes differentiate into macrophages and other monocyte-derived cells such as dendritic cells. Also, circulating monocytes migrate to tissues in response to injury. This process is known as monocyte extravasation and is guided by the chemoattractants produced at the injury site. The interactions between monocyte surface integrins and intercellular adhesion molecules on the endothelial cell surface initiate monocyte extravasation. Different monocyte subsets exhibit distinct migratory properties, enabling them to patrol, arrest, and respond to chemokines during immune responses. Monocytes exert cytotoxic actions against the foreign pathogen. Human monocyte differentiation and maturation are crucial for proper immune function.

Following migration to tissues or body cavities, monocytes are differentiated into macrophages and other monocyte-derived cells. The general functions of macrophages are phagocytosis of cellular debris and pathogens, cytokine production, managing inflammatory responses, and antigen presentation to initiate adaptive immune responses. Macrophages express pattern recognition receptors (PRRs) and co-receptors to identify foreign pathogens. Macrophages are plastic cells; the phenotypical switch of macrophages is known as macrophage polarization. During macrophage polarization, a specific macrophage phenotype is mounted in response to a specific stimulus and/or group of stimuli.

CD11a

CD11a, a member of the integrin family, is widely recognized for its role in leukocyte adhesion and migration. Expressed on monocytes and macrophages, CD11a contributes to immune surveillance and inflammatory responses. Its presence supports cell–cell interactions and facilitates tissue infiltration, making it a useful marker in immunophenotyping studies. Researchers often examine CD11a levels to assess immune cell activation and trafficking. Understanding its expression patterns can aid in exploring disease mechanisms and therapeutic targets in immunology and oncology.

Figure 1. Immunohistochemistry (Formalin/PFA-fixed paraffin-embedded sections) - Anti-CD11a antibody [EP1285Y] (ab52895).

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CD11c

CD11c is a transmembrane protein commonly used to identify monocyte subsets in immunological research. It plays a role in antigen presentation and cell–cell communication, particularly in inflammatory environments. CD11c expression is often elevated in activated monocytes, making it a useful marker for studying immune responses and disease progression. Its detection supports the characterization of monocyte heterogeneity and function in both healthy and pathological conditions. Researchers use CD11c to explore cellular dynamics in autoimmune disorders, infections, and cancer.

Figure 2. Immunohistochemistry (Formalin/PFA-fixed paraffin-embedded sections) - Anti-CD11c antibody [EP1347Y] - C-terminal (ab52632).

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CD14

CD14 is a glycoprotein expressed on the surface of monocytes and plays a role in recognizing bacterial lipopolysaccharides. It supports innate immune responses by facilitating pathogen detection and signaling. CD14 is commonly used to identify classical monocyte populations in flow cytometry and immunological studies. Its expression levels can vary under inflammatory conditions, making it a useful marker for monitoring immune activation. Researchers studying infection, autoimmunity, and cancer often include CD14 in their panels to explore monocyte behavior and function.

Figure 3. Flow Cytometry - Anti-CD14 antibody [SP192] (ab183322).

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CD18

CD18, also known as integrin β2, is expressed on monocytes and contributes to cell adhesion and migration. It forms heterodimers with CD11 molecules, supporting immune cell trafficking and signaling. CD18 is often used in flow cytometry to identify monocyte subsets and assess activation states. Its expression can vary in response to inflammation, infection, and autoimmune conditions. Researchers studying leukocyte dynamics and immune regulation frequently include CD18 in their panels to explore monocyte behavior across diverse biological contexts.

Figure 4. Immunohistochemistry (Formalin/PFA-fixed paraffin-embedded sections) - Anti-CD18 antibody [EPR26929-26] (ab307406).

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CD16a

CD16a, also known as FcγRIIIa, is a low-affinity receptor for IgG found on non-classical and intermediate monocyte subsets. It plays a role in antibody-dependent cellular cytotoxicity and immune complex clearance. CD16a expression helps distinguish monocyte populations with pro-inflammatory and patrolling functions. Researchers use CD16a in flow cytometry panels to study monocyte heterogeneity and immune responses in conditions such as infection, autoimmunity, and cancer. Its presence supports investigations into monocyte-mediated inflammation and therapeutic targeting strategies.

Figure 5. Immunoprecipitation - Anti-CD16 antibody [EPR22409-124] (ab246222).

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CD11a

CD11a, part of the integrin family, is expressed on macrophages and contributes to immune cell adhesion and migration. It pairs with CD18 to form LFA-1, which supports interactions with endothelial cells and antigen-presenting cells. CD11a expression is often evaluated in studies of macrophage activation and tissue infiltration. Its role in cell–cell communication makes it a useful marker in immunophenotyping and inflammation research. Scientists use CD11a to explore macrophage behavior in autoimmune diseases, infections, and tumor microenvironments.

Figure 6. Immunohistochemistry (Formalin/PFA-fixed paraffin-embedded sections) - Anti-CD11a antibody [EP1285Y] (ab52895).

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CD11b

CD11b, also known as integrin αM, is widely expressed on macrophages and supports adhesion, migration, and phagocytosis. It pairs with CD18 to form the Mac-1 complex, which facilitates interactions with endothelial cells and extracellular matrix components. CD11b is frequently used in flow cytometry to identify activated macrophages and study their role in inflammation and immune regulation. Its expression helps researchers explore macrophage responses in infection, tissue repair, and tumor environments, offering insights into immune dynamics across various conditions.

Figure 7. Flow Cytometry - Anti-CD11b antibody [M1/70] (ab8878).

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CD11c

CD11c, an integrin commonly found on macrophages, plays a role in immune cell adhesion and antigen presentation. It is often used to identify activated macrophage populations, especially in inflammatory and infectious contexts. CD11c expression supports studies of macrophage function in tissue remodeling, autoimmunity, and tumor microenvironments. Researchers use CD11c in flow cytometry and transcriptomic profiling to explore macrophage heterogeneity and signaling pathways. Its presence helps characterize immune responses and contributes to understanding macrophage-driven disease mechanisms.

Figure 8. Immunohistochemistry (Formalin/PFA-fixed paraffin-embedded sections) - Anti-CD11c antibody [EP1347Y] - C-terminal (ab52632).

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CD18

CD18, also known as integrin β2, is expressed on macrophages and forms heterodimers with CD11 family members to mediate adhesion, migration, and immune signaling. It plays a role in macrophage interactions with endothelial cells and extracellular matrix components. CD18 is frequently used in immunophenotyping to assess macrophage activation and function in inflammatory and tumor environments. Its expression helps researchers explore macrophage dynamics in tissue remodeling, infection, and immune regulation, supporting studies in both basic and translational immunology.

Figure 9. Immunohistochemistry (Formalin/PFA-fixed paraffin-embedded sections) - Anti-CD18 antibody [EPR26929-26] (ab307406).

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CD64

CD64, also known as FcγRI, is a high-affinity receptor for IgG expressed on macrophages. It plays a role in phagocytosis, antigen presentation, and cytokine production. CD64 is commonly used to identify activated macrophages in inflammatory conditions and infectious diseases. Its expression helps distinguish macrophages from dendritic cells and monocytes in flow cytometry and transcriptomic studies. Researchers use CD64 to explore macrophage function in tissue homeostasis, immune regulation, and chronic inflammation, particularly in sepsis and inflammatory bowel disease contexts.

Figure 10. Western blot - Anti-CD64 antibody [EPR4623] (ab109449).

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CD68

CD68 is a glycoprotein commonly used to identify macrophages in tissue sections and flow cytometry. It is primarily located in lysosomes and endosomes, reflecting the phagocytic activity of macrophages. CD68 expression is associated with both resting and activated macrophage states, making it a reliable marker across various experimental conditions. Researchers use CD68 to study macrophage distribution, activation, and involvement in inflammation, cancer, and tissue remodeling. Its presence supports investigations into immune responses and cellular dynamics in health and disease.

Figure 11. Multiplex immunohistochemistry - Anti-CD68 antibody [SP251] (ab192847).

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CD80

CD80 is a co-stimulatory molecule expressed on activated macrophages, contributing to T cell interaction and immune modulation. It plays a role in antigen presentation and is often upregulated during inflammatory responses. CD80 is used to identify macrophage activation states in studies of autoimmunity, infection, and cancer. Its expression supports investigations into immune checkpoint pathways and cellular communication. Researchers include CD80 in flow cytometry panels to explore macrophage behavior and their role in shaping adaptive immunity.

Figure 12. Flow Cytometry (Intracellular) - Anti-CD80 antibody [EPR1157(2)] (ab134120).

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CD163

CD163 is a scavenger receptor expressed on macrophages, particularly those involved in anti-inflammatory and tissue repair functions. It binds hemoglobin–haptoglobin complexes and contributes to immune regulation. CD163 is often used to identify M2-like macrophages in studies of cancer, infection, and chronic inflammation. Its expression is influenced by cytokines and microbial signals, reflecting macrophage polarization states. Researchers use CD163 to explore macrophage heterogeneity and their role in shaping immune responses, especially in gut, tumor, and wound healing environments.

Figure 13. Multiplex immunohistochemistry - Anti-CD163 antibody [EPR19518] (ab182422).

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CD206

CD206, also known as the mannose receptor, is a surface protein expressed on macrophages involved in tissue repair and anti-inflammatory responses. It helps distinguish M2-like macrophages from other immune cells and is commonly used in studies of chronic inflammation, cancer, and gut immunity. CD206 expression correlates with markers like CD68 and CD163, indicating a mature macrophage phenotype. Researchers use CD206 to explore macrophage polarization and function, particularly in contexts such as inflammatory bowel disease and wound healing.

Figure 14. Flow Cytometry - Anti-Mannose Receptor antibody [15-2] - Low endotoxin, Azide free (ab270634).

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References

1. Novershtern, N., et al. Densely interconnected transcriptional circuits control cell states in human hematopoiesis  Cell   144 ,296-309 (2011).
2. Wood, B. Multicolor Immunophenotyping: Human Immune System Hematopoiesis  Methods Cell Biol.  75 ,559-576 (2004).
3. Yang, J., Zhang, L., Yu, C., et al. Monocyte and macrophage differentiation: circulation inflammatory monocyte as biomarker for inflammatory diseases  Biomark. Res.   2 (1), (2014).
4. Kapellos, T. S., Bonaguro, L., Gemünd, I., et al. Human Monocyte Subsets and Phenotypes in Major Chronic Inflammatory Diseases  Front Immunol   30 (10), (2019).
5. Murray, P. J., Wynn, T. A. Protective and pathogenic functions of macrophage subsets  Nat. Rev. Immunol.  11 ,723-737 (2011).
6. Pilling, D., Fan, T., Huang, D., et al. Identification of markers that distinguish monocyte-derived fibrocytes from monocytes, macrophages, and fibroblasts  PLoS One   4 ,31-33 (2009).