• Product name

    Anti-Human IgG Fab fragment antibody [4A11]
  • Description

    Mouse monoclonal [4A11] to Human IgG Fab fragment
  • Host species

  • Specificity

    This antibody reacts with Fab fragment of human IgG. Specificity was confirmed by western blotting analysis of purified Fab fragment, of human IgG, under reducing conditions.
  • Tested applications

    Suitable for: Flow Cyt, ELISA, WBmore details
  • Species reactivity

    Reacts with: Human
  • Immunogen

    Full length native protein (purified) (Human).

  • Positive control

    • WB: Normal human immunoglobulins. Flow Cyt: Human peripheral blood cells.
  • General notes

    This product was changed from ascites to tissue culture supernatant on 24th January 2018. Please note that the dilutions may need to be adjusted accordingly. If you have any questions, please do not hesitate to contact our scientific support team.


  • Form

  • Storage instructions

    Shipped at 4°C. Store at +4°C short term (1-2 weeks). Upon delivery aliquot. Store at -20°C or -80°C. Avoid freeze / thaw cycle.
  • Storage buffer

    pH: 7.40
    Preservative: 0.097% Sodium azide
    Constituent: PBS
  • Concentration information loading...
  • Purification notes

    Purified by precipitation and chromatography
  • Clonality

  • Clone number

  • Myeloma

  • Isotype

  • Light chain type

  • Research areas


Our Abpromise guarantee covers the use of ab771 in the following tested applications.

The application notes include recommended starting dilutions; optimal dilutions/concentrations should be determined by the end user.

Application Abreviews Notes
Flow Cyt Use at an assay dependent concentration.

ab170192 - Mouse monoclonal IgG2b, is suitable for use as an isotype control with this antibody.

ELISA Use at an assay dependent concentration.
WB Use at an assay dependent concentration.


  • Relevance

    Human IgG consists of four subclasses (1-4) that can be recognised by antigen differences in their heavy chains. Each subclass has different biological and physiochemical properties. The IgG subclass may be preferentially produced in response to different antigens. The Fab fragment (fragment antigen binding) is the antigen region of the IgG molecule. It is composed of one constant and one variable domain of each of the heavy and the light chain.


  • Flow Cytometry analysis of human peripheral blood cells labeling Human IgG Fab fragment with Anti-Human IgG Fab fragment antibody [4A11] (ab771).
  • All lanes : Anti-Human IgG Fab fragment antibody [4A11] (ab771)

    Lane 1 : Normal human immunoglobulins
    Lane 2 : Normal bovine immunoglobulins

    Performed under reducing conditions.
  • Surface staining of human peripheral blood cells with ab771. An APC-conjugated goat anti-mouse IgG was used as the secondary antibody.


This product has been referenced in:

  • Lau YF  et al. An adjuvant for the induction of potent, protective humoral responses to an H5N1 influenza virus vaccine with antigen-sparing effect in mice. J Virol 84:8639-49 (2010). ELISA . Read more (PubMed: 20538850) »
  • Drexler SK  et al. SIGIRR/TIR-8 is an inhibitor of Toll-like receptor signaling in primary human cells and regulates inflammation in models of rheumatoid arthritis. Arthritis Rheum 62:2249-61 (2010). Flow Cyt ; Human . Read more (PubMed: 20506350) »
See all 2 Publications for this product

Customer reviews and Q&As

1-8 of 8 Abreviews or Q&A


We have not performed the blocking assay, but the specificity of this antibody for Fab part of IgG (over Fc) was confirmed by Western blotting using Fab fragments.

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This product will recognize the Fab fragment of any exposed IgG. However if whole IgG is present and not masked by absorption into the substrate, these too will be recognized. I would recommend performing a co stain with an anti- IgG Fc specific antibody to determine whether the signal seen by ab771 is from Fabs or whole IgG. We offer a Chicken polyclonal to Human + Mouse + Rat IgG Fc fragment (ab15866) which you would be able to use as a co-stain with ab771. As this product is also against mouse Fc I would recommend sequential staining first with ab15866 followed by ab771.

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Thank you for ordering the Fab fragment antibody . Unfortunately, the affinity or dissociation constant, Kd, is not determined for this antibody. If you have any other questions, please contact us.

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Thank you for your enquiry. For Western blotting, I would recommend using ab771 at a dilution of 1:1000 and optimizing based upon results. At the bottom of the online datasheet for ab771 there is a list of compatible secondary antibodies which can be used. One suggestion is ab6728 - Rabbit polyclonal to Mouse IgG H and L (HRP). If you are having problems with high background, you may want to try blocking with 3% BSA, increase the number of washes, and decreasing the concentration of primary antibody as well as the incubation period. Please contact us again if you have any additional questions.

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Thank you for your enquiry. The antibody should recognize all human IgG isoforms. The H or L chain specificity has not been determined. If you need any further assistance please contact us again.

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Thank you for your enquiry. The isoelectric point of this antibody has not been determined.

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Regarding ab7498, this particular clone is Fc-specific but the epitope has not been more precisely determined. For ab771, the epitope is unknown. If you have any more questions, please contact us again.

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The originator of these two antibodies has informed me that the anti Fab fragment antibody is better (IgG receptors bind IgG via Fc so it may be occupied). The Fc fragment is not good for IgM bound to the B-cell surface, but is great for soluble IgM.

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