Increase in T cell surface thiol levels are linked with activation and diabetogenicity

Abstract

Abstract Free radicals contribute to Type 1 diabetes (T1D) autoimmune responses. We recently demonstrated that superoxide-deficient CD4 T cells exhibited increased effector responses and diabetogenicity, but the redox-dependent mechanism(s) mediating T cell activation were unclear. We hypothesized that during T1D progression, CD4 T cells with a reduced cell surface state would exhibit a concomitant increase in pro-inflammatory cytokine and chemokine responses. To test this, alexa fluor 647-conjugated maleimide (ALM)-labeling of cell surface reduced thiols on diabetogenic mouse and human CD4 T cells was performed. We observed an increase in ALM percentage and gMFI from peripheral Non-obese diabetic (NOD) mouse CD4 T cells during progression to overt diabetes. Cognate autoantigen stimulation elicited a 2- and 20-fold increase in CD4 ALM T cell percentage and gMFI, respectively. In addition to serving as a T cell activation marker, ALM gMFI of reduced CD4 T cell surface thiols was enhanced (1.2-fold) with Th1 polarization and blunted (12.2-fold) following Treg polarization in contrast to Th0 conditions. Cell surface reduced thiols from human CD4 T cells with recent-onset T1D exhibited elevated ALM percentage (1.6-fold, p < 0.05) and gMFI (1.7-fold, p = 0.1503) in comparison to age-matched healthy controls following polyclonal stimulation. Mirroring the increase in ALM with T1D individuals, PBMCs (n=12) also synthesized increased IFNγ (1.2-fold, p=0.0031), TNFα (1.3-fold, p=0.0022), and CXCL10 (1.2-fold, p=0.0145) in contrast to healthy controls (n=7). Our studies point to the exciting potential that oxidation of cell surface thiols on diabetogenic CD4 T cells could abrogate effector responses and correlate with CD4 T cell activation.