Question

Do TCR subunits function as signal transducers?

A) Yes, by directly phosphorylating target proteins
B) Yes, by binding to MHC molecules
C) No, they rely on associated CD3 signaling molecules
D) No, their only function is antigen recognition

Answer 1

The T-cell receptor (TCR) does not function as a signal transducer; it is responsible for antigen recognition. Instead, the TCR relies on associated CD3 signaling molecules to transduce signals into the T cell when an antigen is recognized.

Step-by-step explanation:

The T-cell receptor (TCR) is a protein dimer embedded in the plasma membrane of a T cell. It plays a crucial role in the recognition of specific antigens presented with major histocompatibility complex (MHC) molecules. While the TCR is responsible for antigen recognition, it does not function as a direct signal transducer.

Instead, the TCR relies on associated CD3 signaling molecules to transduce signals into the T cell when an antigen is recognized. The CD3 signaling molecules contain immunoreceptor tyrosine-based activation motifs (ITAMs) that are phosphorylated upon TCR engagement, leading to signal transduction and subsequent T cell activation.