MHC CLASS I-MEDIATED ANTIGEN PRESENTATION AND INDUCTION OF CD8(-CELL RESPONSES IN AUTOIMMUNE DIABETES-PRONE NOD MICE() CYTOTOXIC T)

The common class I alleles (e.g., K-d and D-b) within the H2(g7) major histocompatibility complex (MHC) clearly contribute to autoimmune IDD M in NOD mice, but the mechanism by which this occurs has been controv ersial, One laboratory has reported that the peptide transporter encod ed by the Tap1 gene within H2(g7) is defective, and this contributes t o IDDM by impairing MHC class I-mediated antigen presentation, If true , defective MHC class I-mediated antigen presentation should segregate with the H2(g7) haplotype, NOD mice, related congenic stocks, and oth er control strains were used to test this hypothesis, H2(g7)-positive strains did not differ from those expressing other MHC haplotypes in a bility to present MHC class I-restricted H3a(a) or H3a(b) minor histoc ompatibility (H) antigens to cytotoxic T-lymphocytes (CTL). The H2(g7) haplotype was found to have a reduced capacity to mediate MHC class I -restricted presentation of the H47(a) minor H antigen, However, MHC c lass I-restricted presentation of H47(a) was found to be Tap independe nt; NOD mice and control strains also did not differ in ability to act ivate adenovirus-specific MHC class I restricted CTL, Thus, the H2(g7) haplotype is not characterized by a Tap gene defect that only impairs the inductive phase of the immune response, In addition, MHC class I- restricted presentation of either minor H or adenoviral antigens was e quivalent in male and female NOD mice, Therefore, while the class I al leles of the H2(g7) haplotype exert diabetogenic functions in NOD mice , this is not elicited through a Tap gene defect, The absence of femal e-specific Tap gene defects also indicates this cannot account for the reduced male incidence of IDDM in some NOD mouse colonies.