Model for the Interaction of T-cell Receptors with Peptide/MHC Complexes

The immune response against a viral infection is mediated by two different types of cells known as B and T lymphocytes. The receptor on the B cell is the well-characterized antibody molecule, which exists in a membrane-bound form and in a secreted form involved in the initiation of complement-mediated killing and the inactivation of viral particles by direct binding. The recognition molecule on T cells is the membrane-bound T-cell antigen receptor, which has specificity for a combination of foreign antigen with a molecule of the major histocompatibility complex (MHC), as first demonstrated by Zinkernagel and Doherty (1974). MHC proteins exist in two closely related forms called class I and class II MHC molecules, both of which are cell-surface glycoproteins that are highly polymorphic in the human population. In general, class II MHC molecules are involved in interactions with T-helper cells, which cooperate with B cells to make antibody