Differences that matter: major cytotoxic T cell-stimulating minor histocompatibility antigens.

Despite thousands of genetic polymorphisms among MHC matched mouse strains, a few unknown histocompatibility antigens are targeted by the cytotoxic T cells specific for tissue grafts. We isolated the cDNA of a novel BALB.B antigen gene that defines the polymorphic H28 locus on chromosome 3 and yields the naturally processed ILENFPRL (IFL8) peptide for presentation by Kb MHC to C57BI/6 CTL. The CTL specific for the IFL8/Kb and our previously identified H60/Kb complexes represent a major fraction of the B6 anti-BALB.B immune response. The immunodominance of these antigens can be explained by their differential transcription in the donor versus the host strains and their expression in professional donor antigen-presenting cells.