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How are an antibody and a B-cell antigen receptor related?
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antibody
The four-chain structure of an antibody, or immunoglobulin, molecule. The basic unit is composed of two identical light (L) chains and two identical heavy (H) chains, which are held together by disulfide bonds to form a flexible Y shape. Each chain is composed of a variable (V) region and a constant (C) region.
An antibody and a B-cell antigen receptor are fundamentally related, as they share the same basic protein structure and antigen-binding specificity. In essence, a B-cell antigen receptor is an antibody molecule that is not secreted but is instead anchored to the B-cell membrane by an extra tail that penetrates the cell membrane.12
The relationship between the two can be summarized as follows:
- Structural Identity: Each antibody molecule is essentially identical to the antigen receptor of the B cell that produced it. Both consist of polypeptide chains arranged in a Y-shaped structure with variable tips that form the antigen-binding site.1
- Functional Continuity: When a B cell’s surface receptor recognizes and binds to a specific antigen, the cell is stimulated to divide and differentiate into plasma cells. These plasma cells then secrete large quantities of antibodies that are modeled after the original surface receptors, allowing them to target and neutralize the same specific antigen throughout the body.134
While the receptor remains fixed to the cell to facilitate recognition, the secreted antibody acts as a mobile, protective protein to eliminate foreign substances.12