Which of the following statements is true?


a. An antibody has one antigen-binding site.
b. A lymphocyte has receptors for a single antigen.
c. Every antigen has a single epitope.
d. A liver or muscle cell makes two classes of MHC molecule.

Verified step by step guidance

1. Identify the basic functions and structures of antibodies, lymphocytes, antigens, and MHC molecules.
2. Understand that an antibody typically has two antigen-binding sites, not one, allowing it to bind to two identical epitopes on antigens.
3. Recognize that a lymphocyte, specifically a B-cell, has receptors that are specific to a particular antigen, meaning it can bind to one type of antigen.
4. Consider that antigens can have multiple epitopes, which are the specific parts of an antigen that an antibody recognizes and binds to.
5. Review the roles of MHC (Major Histocompatibility Complex) molecules, noting that liver and muscle cells, like most nucleated cells, produce MHC class I molecules. Only certain cells like dendritic cells, macrophages, and B cells produce both MHC class I and class II molecules.

Key Concepts

Antibodies and Antigen-Binding Sites

Antibodies are specialized proteins produced by B cells that recognize and bind to specific antigens. Each antibody typically has two identical antigen-binding sites, allowing it to bind to two identical epitopes on an antigen, enhancing its ability to neutralize pathogens.

Lymphocyte Receptors

Lymphocytes, particularly T and B cells, express receptors that are specific to particular antigens. A single lymphocyte is programmed to recognize only one specific antigen, which is crucial for the adaptive immune response, allowing for targeted action against pathogens.

Epitopes and Antigens

An epitope is the specific part of an antigen that is recognized by the immune system, particularly by antibodies, B cells, or T cells. Many antigens can have multiple epitopes, allowing them to elicit a diverse immune response, contrary to the statement that every antigen has a single epitope.