Final answer:
Antibody isotypes differ in structure, function, distribution, and effector functions, with structural variations primarily found in the heavy chains. Each class (IgM, IgD, IgG, IgA, and IgE) plays specific roles in the immune response, from pathogen neutralization to complement activation, but all share the same antigen specificity.
Step-by-step explanation:
Antibody isotypes and subtypes differ in various aspects of their structure, function, distribution, and effector functions, although they do not have different antigen specificity. The structural differences are mainly in the heavy chains of the antibodies. For instance, IgM is a pentamer while IgG is a monomer. In terms of function, the five classes of antibodies each play a distinct role in the immune response. IgG circulates in body fluids, binding pathogens, while IgE is involved in allergic responses and protection against parasites. Functionally, antibodies can neutralize pathogens, opsonize them for phagocytosis, agglutinate them, activate complement, and facilitate antibody-dependent cell-mediated cytotoxicity.
The distribution of antibodies varies, for example, IgA is found predominantly in mucosal areas, whereas IgG is distributed broadly throughout the body. As for effector functions, each antibody class has different roles, like IgM being primarily responsible for complement activation during the initial stages of an immune response.