Understanding Immunoglobulins: The Role of Antigen Specificity in Immune Response

The various classes of immunoglobulins are differentiated on the basis of their A) asymmetry.B) antigen specificity.C) light-chain variable segments.D) heavy-chain constant segments. E) reactivity.

The correct answer is B) antigen specificity

The correct answer is B) antigen specificity.

Immunoglobulins, also known as antibodies, are proteins produced by B cells in response to the presence of foreign substances called antigens. They play a crucial role in the immune response by specifically binding to and neutralizing these antigens.

The different classes of immunoglobulins, also known as isotypes, have distinct functions and are produced at different stages of an immune response. These isotypes are IgM, IgD, IgG, IgA, and IgE. They are differentiated on the basis of their antigen specificity, which refers to their ability to bind to specific antigens.

Each immunoglobulin isotype has a characteristic structure consisting of two heavy (H) chains and two light (L) chains, which are held together by disulfide bonds. The antigen-binding region of the immunoglobulin, also known as the variable region, is located at the tip of the “Y” shape formed by the H and L chains. It is in this region that the antigen binding occurs.

The variable region of the immunoglobulin consists of both heavy-chain variable segments and light-chain variable segments. These segments contribute to the antigen specificity of the immunoglobulin by encoding for a wide variety of antigen-binding sites. Through genetic recombination and somatic hypermutation, B cells can generate a diverse repertoire of immunoglobulins with different antigen specificities.

However, it is important to note that while the variable segments contribute to the antigen-binding specificity, they do not differentiate the various classes of immunoglobulins. The heavy-chain constant segments, on the other hand, determine the class or isotype of the immunoglobulin. Each class of immunoglobulin has a different heavy-chain constant segment that confers specific effector functions, such as complement activation, antibody-dependent cell-mediated cytotoxicity, and mucosal defense.

In summary, the various classes of immunoglobulins are differentiated based on their antigen specificity, while the heavy-chain constant segments determine their unique functions and properties.

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