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 antigens.
c. An antigen can have different epitopes.
d. A liver or muscle cell makes one class of MHC molecule.

Verified step by step guidance

1. Understand the role of antibodies: Antibodies are proteins produced by the immune system to identify and neutralize foreign objects like bacteria and viruses. Each antibody has multiple antigen-binding sites, typically two, allowing it to bind to antigens.
2. Examine lymphocyte receptors: Lymphocytes, such as B cells and T cells, have receptors on their surfaces. Each lymphocyte is specific to a single antigen, meaning it has receptors for only one type of antigen, not multiple different antigens.
3. Explore antigen structure: Antigens are substances that can induce an immune response. They can have multiple epitopes, which are specific parts of the antigen that antibodies or receptors bind to.
4. Review MHC molecules: Major Histocompatibility Complex (MHC) molecules are proteins found on the surface of cells that present antigen fragments to T cells. Different cells express different classes of MHC molecules. For example, liver or muscle cells typically express MHC class I molecules.
5. Identify the incorrect statement: Based on the understanding of antibodies, lymphocytes, antigens, and MHC molecules, determine which statement does not align with biological principles. Focus on the statement about lymphocyte receptors, as it contradicts the specificity of lymphocytes to a single antigen.

Key Concepts

Antibody Structure

Antibodies are Y-shaped proteins produced by B cells that have multiple antigen-binding sites, typically two, allowing them to bind to specific antigens. These binding sites are located at the tips of the 'Y' and are highly variable, enabling the immune system to recognize a vast array of antigens.

Lymphocyte Receptors

Lymphocytes, such as B cells and T cells, have receptors that are specific to one type of antigen. Each lymphocyte is equipped with receptors that recognize a unique antigen, ensuring a targeted immune response. This specificity is crucial for the adaptive immune system's ability to remember and respond to pathogens.

Major Histocompatibility Complex (MHC)

MHC molecules are proteins found on the surface of cells that present antigen fragments to T cells. There are two main classes: MHC class I, present on almost all nucleated cells, and MHC class II, found on specialized antigen-presenting cells. Liver and muscle cells typically express MHC class I molecules, which are essential for presenting intracellular antigens to cytotoxic T cells.