Detection of glutamic acid decarboxylase-activated T cells with I-A(g7) tetramers

CD4(+) T cells selected by the type 1 diabetes associated class II MHC I-A( g7) molecules play a critical role in the disease process. Multivalent MHC/ peptide tetramers have been used to directly detect antigen-specific T cell s. Detection of autoantigen-activated CD4(+) T cells with tetramers should be Very helpful in the study of the roles of these cells in diabetes. We re port here the generation of tetramers of I-A(g7) covalently linked to two g lutamic acid decarboxylase (CAD) peptides and the detection of GAD peptide- activated T cells from nonobese diabetic (NOD) mice. The I-A(g7) heterodime rs can form stable complexes with a covalently bound GAD peptide and can st imulate antigen specific T cells, Furthermore, I-A(g7)/GAD peptide tetramer can detect most if not all of the antigen-specific CD4(+) T cells from imm unized NOD mice. Antigen-specific T cells detected by the tetramers can up- regulate their CD4 expression on the cell surface after being restimulated with the CAD peptides in vitro. In contrast, the tetramers can detect a per centage of T cells in lymph nodes and spleens and T cells infiltrating isle ts from nonimmunized mice that is not significantly above the background, T herefore, T cells specific for the CAD peptides are present in NOD mice at a frequency too low to be detected, but immunization of NOD mice can facili tate their detection by tetramers.