FIGURE 3.7 Antibody molecule. Antibodies are composed of two identical heavy chains

and two identical light chains, held together by disulfide bonds. The variable region of the

heavy and light chains create the antigen-binding capacity of the molecule. The constant

region, also referred to as the Fc domain of the antibody, interacts with other elements of the

immune system to trigger various effector functions.

FIGURE 3.8 Antibody diversity. Antibodies are divided into different classes and their

nomenclature is based on the heavy chain isotype. Therefore, antibodies made up of γ, υ, δ, α

and e chains are named IgG, IgM, IgD, IgA, and IgE, respectively. An additional chain, the

joining or J chain stabilizes the dimeric structure of IgA and pentameric structure of IgM.

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