Regulatory and effector CD4 T cells in nonobese diabetic mice recognize overlapping determinants on glutamic acid decarboxylase and use distinct V beta genes

The 524-543 region of glutamic acid decarboxylase (GAD65), GAD65(523-543), is one of the first fragments of this islet Ag to induce proliferative T ce ll responses in the nonobese diabetic (NOD) mouse model of spontaneous auto immune diabetes. Furthermore, NOD mice given tolerogenic doses of GAD65(524 -543) are protected from spontaneous and cyclophosphamide-induced diabetes. In this study, we report that there are at least two I-A(g7)-restricted de terminants present in the GAD65(524-543) sequence, each capable of recruiti ng unique T cell repertoires characterized by distinct TCR VP gene use. CD4 (+) T cells arise spontaneously in young NOD mice to an apparently dominant determinant found within the GAD65 peptide 530-543 (p530); however, T cell s to the overlapping determinant 524-538 (p524) dominate the response only after immunization with GAD65(524-543). All p530-responsive T cells used th e V beta4 gene, whereas the V beta 12 gene is preferentially used to encode the TCR of p524-responsive T cell populations, T cell clones and hybridoma s from both of these T cell groups were responsive to APC pulsed with GAD65 (524-543) or a hole rGAD65. p524-reactive cells appeared to be regulatory u pon adoptive transfer into young NOD mice and could inhibit insulin-depende nt diabetes mellitus development, although they were unable to produce IL-4 , IL-10, or TGF beta upon antigenic challenge. Furthermore, we found that i ,p, injection with p524/IFA was very effective in providing protection from cyclophosphamide-induced insulin-dependent diabetes mellitus, These data d emonstrate that the regulatory T cells elicited by immunizing with GAD65(52 4-543) are unique and distinct from those that arise from spontaneous endog enous priming, and that T cells to this limited region of GAD65 may be eith er regulatory or pathogenic.