Our two related aims are to examine the T cell repertoire against beta cell peptides selected by the I-Ag7 molecules of the NOD mouse. And to relate this autoreactivity to the biochemical parameters of peptide selection and binding by the presenting cells bearing the I-Ag7 molecules. Our focus relates the biochemistry of peptide selection to the specificity and biology of diabetogenic T cells. Our approaches should identify the spectrum of antigens targeted in autoimmune diabetes through: i) the analysis of the Ag7-peptidome from beta cells, using mass spectrometry analysis of peptides. To do this we have generated insulinoma cell lines bearing I-Ag7 by expressing in them the CIITA transactivator. This line selects for beta cell peptides recognized by spontaneous diabetogenic CD4 T cells. The mass spectrometry procedures involve new approaches for peptide separation and detection, and for computational analyses of the data sets. ii) a complementary approach that utilizes an analysis of beta cell specific genes, together with computational programs to predict the best peptides selected by I-Ag7, from the proteins encoded by them. The beta cell transcriptome has just been obtained from our collaborator, Kanagawa, now working at Riken in Japan. iii) a biochemical analysis of the interaction between the identified peptides and I-Ag7 to determine binding parameters including affinity, dissociation rates and occupancy of MHC molecules iv) a cellular cloning strategy to identify the diabetogenic T cells in islets and in the pancreatic lymph nodes; and testing their biological role in diabetogenicity, including a possible cooperative role with islet-reactive CD8+ T cells. We believe our modus operandi will allow us to answer the following questions: What are the target antigens of islet 2 cells? Among these, are there some that are involved in initiation of the autoimmune response against islet 2 cells? As disease progresses, are there defined sets of antigens that maintain islet inflammation and if so, is the T cell reactivity against these distinct from the early targets?PROJECT NARRATIVE ? ? We are examining for the nature of the antigens involved in the pathogenesis of autoimmune diabetes (using the NOD model of spontaneous disease). We are planning to examine the composition of the peptide antigens and to determine which react with the T cells that cause diabetes. Our investigations combine biochemistry with T cell biology. ? ? ?
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