On the peptide model of allorecognition: cytotoxic T lymphocytes recognize an alloantigen encoded by two HLA-linked genes.

The peptide model of allorecognition hypothesizes that alloreactive cytotoxic T lymphocytes recognize peptides associated with major histocompatibility complex (MHC) molecules. This study characterizes an unusual alloantigen that is recognized by two human cytotoxic T-cell lines and may represent a complex formed by the association of a naturally selected peptide with an MHC molecule. Family studies demonstrate that both components of the alloantigen are products of MHC-linked genes. One component is a class I molecule most likely encoded by the HLA-B locus. The second component is encoded by an MHC-linked gene that shows a limited polymorphism; whether it represents the product of a second class I gene or of some other MHC gene remains to be determined. These data provide experimental evidence supporting the peptide model of allorecognition in human beings and indicate that some naturally selected peptides involved in allorecognition may be derived from MHC-encoded proteins.