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What are isotype controls used for? How to find the right control antibody?

Isotype control antibodies

Isotype controls are negative controls that indicates the amount of background signal of the primary antibody. An isotype control would be either myeloma-derived antibodies of unknown specificity, or raised against an antigen that is presumed not to be present in the cells being studied.

Ideally, the isotype control should match the species, the heavy chain (IgA, IgG, IgD, IgE, or IgM), subclass and light chain (kappa, lambda) class of the primary antibody. If using a directly labeled primary antibody, it is important to select an isotype control conjugated to the same fluorochrome or label as the test antibody. Using a fluorochrome with a similar spectrum is not sufficient.


Particularly in procedures using antibodies it’s very important to prevent any non-specific binding of primary and secondary antibodies by using non-specific isotype controls. At antibodies-online you can obtain more than 3,500 validated isotype controls for all common isotypes. Directly conjugated isotype controls with biotin, AP, Alexa and many other conjugates are available. Browse our products, and narrow down your selection further according to antigen, application, reactivity type and clonality.


Why use isotype controls?

Isotype controls would indicate the amount of non-specific binding to the tissues or cells being examined. Antibodies raised in mice (e.g. IgG2a), for example, bind strongly to some human leukocytes regardless of the specificity of the test antibody. In this case, a mouse IgG2a isotype control would be needed with human cells or tissues to properly assess experimental results.

Non-specific binding of primary antibodies are typically caused by the following reasons:

  • Non-specific Fc receptor binding to cells
  • Non-specific antibody interactions with cellular proteins
  • Cell autofluorescence

Applications for isotype controls

Isotype controls are typically used as a control in flow cytometry (FACS). An isotype control antibody can be used as a standard, blocking agent or coating protein in various scientific applications such as , , , , and .


Hint: Browse through more than 3,500 isotype control antibodies.