Antibody isotyping involves determining the class (e.g., IgG vs. IgM) and subclass (e.g., IgG1 vs. IgG2a) of a monoclonal antibody. This is a critical step in antibody production, as it is necessary for choosing an appropriate purification and modification method for the antibody. For example, if an antibody is determined to be IgM, it cannot be purified effectively with Protein A or G, and it will most likely require fragmentation for use in immunohistochemical procedures. If a monoclonal antibody is determined to be IgG1 composed of kappa light chains (VL-kappa), there is a good possibility that immobilized Protein L can be used to purify it from culture supernatant without contamination of bovine immunoglobulins from the serum supplement. Isotyping is most easily accomplished with commercial, ready-to-use antibody isotyping kits.
Creative Diagnostics® antibody isotyping strip kits are one of most available. These kits include membranes designed to directly capture and react with antibody from the test sample. Antibody isotyping kits produce colored bands on the membrane where the isotype-specific antibodies react with the test antibody. Antibody isotyping kits are faster for testing one sample at a time.