Pathogenesis and Prevention of Type I Diabetes in the Nod Mouse and Man

McDevitt, Hugh

Abstract

Susceptibility to juvenile onset insulin dependent diabetes mellitus (IDDM) is linked to two HLA DQ alleles--HLA DQ8 and HLA DQ2. Because of the great difficulty in isolating DQ restricted human T cell clones, information on the specificity of the DQ restricted T cell response to islet cell antigens is non-existent. Susceptible HLA DQ alleles lack aspartic acid in DQB position 57. (DQ8) exhibits striking differences in binding a number of peptide binding in comparison to DQ9, which is DQbeta57Asp+, and otherwise identical to DQ8. T/H2 CD4 + T/H1 T cells cause islet beta cell destruction. Islet antigen specific T/h2 cells are protective. One mechanism for DQ associated susceptibility is that susceptible alleles bind and present a distinct subset of peptides which induce a predominant T/H1 response. Resistant alleles binding other islet antigen peptides which induce a T/h2 responses. The proposed experiments will test whether susceptible and resistant alleles bind and present different subsets of peptides. This will be done by the production of transgenic mice expressing the relevant HLA DQ alleles, as well as human CD4, in the presence and absence of murine CD4. HLA DQ8.huCD4 transgenic mice at backcross 5 to NOD have been observed develop type I diabetes. Transgenic mice and non-transgenic littermate controls will be monitored for the spontaneous development of auto- antibodies to islet cell antigens and HLA DQ restricted T cell responses to GA65 and pre pro-insulin. Untreated transgenic mice and transgenic mice immunized with recombinant human GD65 and pre pro-insulin will be used to assess the peptides presented by DQ8, DQ7 and DQ6 to T cells. This will be done by using lymph node and spleen T cells from these mice to the murine T cell hybridoma, DW5147. The resulting hybridomas will be analyzed for HLA DQ restriction and peptide specificity. Finally, those peptide epitopes presented by HLA DQ8 will be used to detect HLA DQ restricted responses in pre-diabetic and recent onset diabetic patients.