What is the purpose of an isotype control?

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To estimate the contribution of the non-specific interaction and Fc receptor binding, staining protocols using an antibody directed to an irrelevant antigen (for example, DNP) having the same isotype as the antibody of interest may be analyzed in parallel with the antibody of interest. The antibody directed to the irrelevant antigen is known as the isotype control.

Antibodies are useful for identifying and localizing proteins and other antigens both on the surface of cells as wells as inside cells. The utility of antibodies lies in their specificity and avidity for their antigens, an interaction which is mediated by the antigen binding sites. Antibodies can also react with components other than their antigens in several ways. They can associate with cellular components by non-specific protein-protein interactions. They can associate with fatty components by hydrophobic interaction. Antibodies can also bind to antibody receptors expressed on the surface of some cell types. For example, antibodies of the IgG class can bind to the cell surface Fc receptors known as CD16, CD32, and CD64. Under ideal conditions, various types of non-specific binding will be prevented by including blocking proteins (BSA, milk, or animal serum products) in antibody incubation reaction mixtures. Antibody binding to Fc receptors can be prevented by preincubation of cells with serum preparations containing immunoglobulins.

Answer Id: E5165

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