Studies proposed in this application deal with two overall areas. First, we shall use cloned T lymphocytes to investigate determinants associated with HLA class II molecules. Despite the accumulating information at the genetic and protein levels regarding HLA class II genes and their products, very little is known about polymorphism, as recognized by T lymphocytes, associated with the individual alphabeta products. The polymorphism defined with homozygous typing cells (HTCs) does not allow conclusions regarding polymorphism of individual products that carry determinants contributing to the specificities defined with HTCs. Products to be evaluated include HLA-DR alphabeta-1, DR alphabeta-2, and DQ alphabeta. To the extent that additional DR or DQ dimers are expressed, or that additional class II genes exist that are in linkage disequilibrium with DR/DQ and that are expressed, polymorphism associated with those products will also be studied. Both cloned proliferating, non-cytotoxic and cytotoxic clones will be used. Our emphasis will be on DR2+ and the DR4+ haplotypes, given the existence of the multiple Dw subtypes of each of these serologically-defined specificities and the importance of these haplotypes in a number of associations of HLA and disease. These studies will be done in normal individuals and should contribute to the understanding of HLA as it relates to transplantation. Second, we plan to study associations of HLA class II genes/products and insulin-dependent diabetes (IDD). Sequencing of expressed class II DR and DQ genes from patients with IDD will be performed in an attempt to identify sequences within one or more of those genes that are present more (or less) frequently in IDD patients than in normal individuals. Such sequences may serve as better markers for IDD than are presently available and, to the extent that these sequences are of import functionally in IDD patients, may help us to understand the pathogenesis of the disease. In addition to DNA sequencing, other methods will be used in an attempt to pinpoint the degree of conservation/polymorphism of sequences of interest in IDD patients expressing a given combination of serologically-defined specificities of DR and DQ. We consider it a strength of this application that the same cells proposed herein for study have been and are continuing to be studied by a variety of methods.