Spontaneous diabetes mellitus syndrome in the rat. IV. Immunogenetic interactions of MHC and non-MHC components of the syndrome.

We have examined the frequency of three phenotypic characteristics of the syndrome of spontaneous diabetes (overt IDDM, lymphocytic infiltration of the pancreas, and depression of T lymphocytes) in the offspring of crosses between IDDM BB rats and rats of strains with the same and different RT1 genotypes. On the basis of these observations we propose that there are at least three components of the diabetic syndrome in the rat: (1) a requirement for the RT1u haplotype from the BB strain or a gene in close linkage with the gene coding for this haplotype, (2) a susceptibility for development of insular, periductular, or intraacinar lymphocytic infiltration in the pancreas, and (3) a susceptibility to depression of T lymphocytes. Interactions between these components as well as with other genetic and environmental factors contribute to the full expression of the syndrome.