What are the receptors on T lymphocytes that recognize antigens presented by MHC molecules called?

• A. T cell receptors
• B. B cell receptors
• C. NK cell receptors
• D. Antigen-presenting receptors

Answer: (A)

T cell receptors are the receptors on T lymphocytes that recognize antigenic peptides bound to MHC molecules. These receptors are membrane-bound heterodimers that specifically bind peptide fragments displayed by MHC class I or II on antigen-presenting cells, with co-receptors CD8 or CD4 helping to stabilize the interaction and deliver the signal. This is distinct from B cell receptors, which bind intact or conformational epitopes on native antigens, and from NK cell receptors, which recognize other ligands rather than peptide–MHC complexes. Antigen presentation is carried out by MHC molecules, not by a separate “antigen-presenting receptor.”