What serves as the basis for classifying antibodies?

The classification of antibodies is fundamentally based on the type of heavy chain present in their structure. Antibodies, also known as immunoglobulins, are composed of two heavy chains and two light chains. There are five major classes of immunoglobulins—IgG, IgA, IgM, IgD, and IgE—each identified by their unique heavy chain structure.

The heavy chains differ in their amino acid sequences and determine the function and response of the antibody in the immune system. For instance, IgG has a different heavy chain than IgM, which affects how these antibodies interact with antigens and elicit immune responses. Consequently, the classification reflects differences in the biological activities, distribution in the body, and roles in immune protection.

Other aspects, like the type of light chain, the number of peptide bonds, or presence of antigens, do not serve as the primary basis for antibody classification. The light chain can also be either kappa or lambda, but this does not define the antibody class. Peptide bond count is not relevant to classification, and while antibodies do indeed interact with antigens, this interaction does not provide a basis for their classification. Thus, the type of heavy chain is the key factor in defining an