What is the primary function of the T cell receptor?

The primary function of the T cell receptor is to recognize and bind to MHC (Major Histocompatibility Complex) molecules, which present peptide antigens derived from pathogens. This recognition is crucial for T cell activation and subsequent immune responses. When a T cell receptor interacts with a peptide-MHC complex, it triggers a series of intracellular signaling pathways that result in T cell proliferation, differentiation, and the initiation of an adaptive immune response.

This interaction specifically allows T cells to differentiate between self and non-self, ensuring that the immune system targets foreign structures while maintaining tolerance to the body’s own tissues. MHC molecules are classified into two classes: Class I molecules present endogenous antigens to CD8+ cytotoxic T cells, while Class II molecules present exogenous antigens to CD4+ helper T cells. This specificity is vital for effective immune surveillance and response to infections or malignancies.

Recognizing the role of the T cell receptor in binding to MHC molecules underpins much of the adaptive immune response and illustrates why this function is central to the immune system's recognition capabilities.