Final answer:
The constant domains in antibodies have immunological functions and determine the mechanism of action of the corresponding antibody class.
Step-by-step explanation:
The constant domains in antibodies have immunological functions and determine the mechanism of action of the corresponding antibody class. The variable domains determine the binding specificity of the antibody.
The number of constant domains is different for each antibody class, with IgG having three constant domains, IgA and IgD having three constant domains, and IgM and IgE having four constant domains.