Which of the following statements is not true? (A) An...

Which of the following statements is not true?
(A) An antibody has more than one antigen-binding site.
(B) A lymphocyte has receptors for multiple different
(C) antigens.
(C) An antigen can have different epitopes.
(D) A liver or muscle cell makes one class of MHC molecule.

Key Concepts

Epitopes

Epitopes are the precise parts of an antigen that are recognized by an antibody or a T-cell receptor. A single antigen can present multiple epitopes, meaning that it can be recognized by different immune receptors, contributing to the complexity and versatility of the immune response.

MHC Molecules

Major Histocompatibility Complex (MHC) molecules are proteins expressed on cell surfaces that present peptide fragments to T cells. Different cell types express distinct classes of MHC molecules—most nucleated cells display MHC class I, while specialized antigen-presenting cells express MHC class II—playing a crucial role in immune recognition and response.

Antibody Structure

Antibodies are Y-shaped proteins made of two heavy chains and two light chains. The structure includes at least two antigen-binding sites that allow them to bind simultaneously to one or more copies of the same epitope on an antigen, which is essential for effective immune responses.

Lymphocyte Receptor Specificity

Each lymphocyte, such as a B cell or T cell, is engineered through gene rearrangement to express a receptor that is highly specific for a single antigen. This specificity allows the immune system to target a vast array of pathogens without cross-reactivity, reinforcing the idea that a lymphocyte does not have receptors for multiple different antigens.

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