Isotype Controls

An isotype control is an antibody classified as a negative control which lacks specificity to the target. The isotype control matches the primary antibody in terms of the type and class of antibody used in the application. The purpose of an isotype control is to measure the level of non-specific background staining which occurs.

When choosing which isotype control to use for flow cytometry you should match the antibody to the same host species, immunoglobulin and subtype as your primary antibody. The isotype control should also have the same fluorescent label or conjugate, dose and concentration as the primary antibody and it should be purified from unimmunized animal serum. Ensuring the isotype control criteria matches the primary antibody will help with the detection of non-specific staining caused from the primary antibody, reducing the risk of false-positive results.
It is essential that both the isotype control and the primary antibody are handled in the same conditions, with the same protocol and the samples used are treated the same.