The T-cell antigen receptor is similar to immunoglobulin molecules in that it:

The T-cell antigen receptor is similar to immunoglobulin molecules in that it:

• A. Remains bound to the cell surface and is never secreted
• B. Contains V and C regions on each of its chains
• C. Binds complement
• D. Can cross the placenta and provide protection to a fetus

Answer: (B)

The correct choice is that the T-cell antigen receptor (TCR) contains variable (V) and constant (C) regions on each of its chains. This structure is similar to that of immunoglobulin molecules, which also feature these regions. The variable regions are responsible for the antigen-binding specificity, while the constant regions are involved in signaling and defining the class of the antibody. This similarity in structure is key to understanding how both TCRs and immunoglobulins function in the immune response. While TCRs and immunoglobulins both originate from genetic rearrangements that create diverse antigen receptors, their specific engagement with antigens reflects this critical structural similarity. Regarding the other options, while it is true that TCRs remain on the cell surface and are not secreted, this is a distinct characteristic of their function rather than a similarity to immunoglobulins, which can be secreted. Immunoglobulins do not bind complement in the same manner as TCRs, as TCRs primarily engage with peptide fragments presented by major histocompatibility complex (MHC) molecules. Additionally, the ability to cross the placenta and provide passive immunity is a property associated with immunoglobulin G (IgG) antibodies, not

The correct choice is that the T-cell antigen receptor (TCR) contains variable (V) and constant (C) regions on each of its chains. This structure is similar to that of immunoglobulin molecules, which also feature these regions. The variable regions are responsible for the antigen-binding specificity, while the constant regions are involved in signaling and defining the class of the antibody.

This similarity in structure is key to understanding how both TCRs and immunoglobulins function in the immune response. While TCRs and immunoglobulins both originate from genetic rearrangements that create diverse antigen receptors, their specific engagement with antigens reflects this critical structural similarity.

Regarding the other options, while it is true that TCRs remain on the cell surface and are not secreted, this is a distinct characteristic of their function rather than a similarity to immunoglobulins, which can be secreted. Immunoglobulins do not bind complement in the same manner as TCRs, as TCRs primarily engage with peptide fragments presented by major histocompatibility complex (MHC) molecules. Additionally, the ability to cross the placenta and provide passive immunity is a property associated with immunoglobulin G (IgG) antibodies, not