The guinea pig I region. II. Functional analysis.

We have examined whether an association exists between specific Ia antigen genes and Ir genes which are encoded within the same haplotype. Functionally monospecific sera to the Ia antigens of the guinea pig MHC were selective in their ability to inhibit antigen-specific T-cell proliferation and we were thus able to demonstrate an association between individual Ia specificities and specific Ir genes. The results of these studies in inbred animals were confirmed by examining the association of Ir genes and Ia antigens in the outbred guinea pig population. Of great interest was the observation that antisera made against cross-reactive Ia antigens of strains lacking specific Ir genes would still inhibit immune responses of strains possessing the Ir gene, if the Ir gene was associated with that Ia antigen in the responder strain.