Affinity of T cells for chromogranin A remain constant in type I diabetic NOD mice. (P4119)

Abstract

Abstract In type 1 diabetes numerous autoantigens have been identified in the non-obese mouse model including insulin B 9-23, chromogranin A (ChgA29-42), and glutamic acid decarboxylase 65 (GAD65) to list a few, but the kinetics of antigen specificity during the progression from insulitis to overt diabetes is not known. A T cell clone, BDC2.5, isolated from a diabetic NOD was recently identified as being reactive to ChgA. The two-dimensional (2D) micropipette adhesion frequency assay was able to determine that BDC2.5 TCR transgenic cells specifically recognize ChgA29-42, albeit with 100-fold lower affinity compared to the highly stimulatory mimotope. As this TCR was originally derived from a diabetic NOD, we wanted to see if this highly sensitive assay could detect ChgA29-42 specific cells in the pancreatic lymph nodes (PLN) of diabetic NODs. ChgA29-42 specific CD4 T cells were detected in the PLN at a high frequency and their 2D effective affinity was not statistically different from the BDC2.5 affinity for ChgA29-42. Tracking both the frequency and affinity of antigen specific cells isolated from normoglycemic to overtly diabetic female NOD mice, we have determined that the frequency of antigen specific cells present in the PLN but not the overall affinity range changes for ChgA29-42 between these time points. Thus the micropipette adhesion frequency assay allows one to track the frequency and affinity of antigen specific T cells during the progression to autoimmune disease.