A healthy 45-year-old child-care worker becomes infected with a virus and develops a sore throat, cough, and fever. Infected cells in the bronchial mucosa of this patient process virus-encoded proteins through an intracellular pathway and display peptides derived from the protein on the cell surface bound to class I MHC molecules. CD8⁺ T cells migrate to the mucosa and recognize these peptide-MHC complexes. Which of the following components of the TCR actually bind to the viral peptide-MHC complex?

Question

Quizplus · Accepted Answer

Each α and β chain of the T cell receptor (TCR) contains both a constant and a variable domain. The variable domain contains short stretches of amino acids where the variability between different TCRs is concentrated, and these form the hypervariable or complementarity-determining regions (CDRs). Three CDRs in the α chain are juxtaposed to three similar regions in the β chain to form the part of the TCR that specifically recognizes peptide-MHC complexes. The variable regions of Ig molecules may undergo hypermutation during humoral immune responses, but this does not happen in TCRs. Congenic does not refer to a part of a protein, but rather to an inbred strain of animal. Peptide-binding grooves are part of MHC molecules, not TCRs.

A Healthy 45-Year-Old Child-Care Worker Becomes Infected with a Virus