Phenotypic and functional characterization of adaptive regulatory T cells using a novel TCR-transgenic mouse model of EAE (152.29)

Abstract

Abstract A defect in functions of Foxp3+ CD4 T helper cells called regulatory T cells (Tregs) play Tregs results in the onset of autoimmune diseases, however the basis for these Treg defects and specific roles of nTregs and aTregs and their relative contributions in autoimmunity remain unknown. We have developed a novel mouse model (1B3) that allows for the direct study of the aTreg population, with a defined TCR specificity and autoreactive potential. 1B3 mouse when bred to RAG2-/- background developed spontaneous EAE by 2-3 weeks of age. 1B3.RAG-/- mice had significant number of Foxp3+ cells in periphery but there was a complete lack of Treg generation in the thymus. aTregs isolated from 1B3.RAG-/-exhibited CpG demethylation in TSDR and showed suppressive activity in vitro. Microarray analysis demonstrated that compared to nTregs, aTregs displayed significantly lower levels of surface markers PD-1, Nrp-1 and previously described transcription factor Helios. PD-1 and Nrp-1 allowed us to separate Foxp3+ Tregs into Helios+/hi nTregs and Helios-/lo aTregs in WT NOD or B6 mice. This is the first report describing phenotypic markers to distinguish aTregs from nTregs. aTregs were less effective in controlling effector T cells and exhibited unstable Foxp3 expression in vivo. Thus nTregs are critical in maintaining tolerance while aTregs are generated in periphery to control local inflammatory response but may not provide long lasting protection due to less stable Foxp3 expression.