PATHOLOGY

Detailed explanation-1: -A T-cell receptor recognizes antigen in the form of a complex of a foreign peptide bound to an MHC molecule. 3-12. T cells with different functions are distinguished by CD4 and CD8 cell-surface proteins and recognize peptides bound to different classes of MHC molecule.

Detailed explanation-2: -T cells use their surface receptor, called T cell receptor or TCR, to recognise peptides presented by major histocompatibility complex (MHC) molecules. The peptide presented by MHC can be derived from the host proteins (self-peptides), pathogens (virus and bacteria), or tumours.

Detailed explanation-3: -Unlike antibody, the TCR cannot bind antigen directly. Instead it needs to have broken-down peptides of the antigen ‘presented’ to it by an antigen presenting cell (APC). The molecules on the APC that present the antigen are called major histocompatibility complexes (MHC).