Enhanced induction of CD4+CD25+FOXP3+ suppressive function in memory versus naïve CD4+CD25-FOXP3- T-cells is proportional to strength of activating stimulus. (50.2)

Abstract

CD4+CD25+FOXP3+ regulatory T-cells (Tregs) play a vital role in suppressing autoimmune responses. We have previously shown that, in humans, all activated T-cells attain a state of transient FOXP3 expression that correlates with transient suppressive ability. In fact, peripheral generation of induced Tregs (iTregs) is likely the dominant source of regulatory cells in healthy adults. Through the use of a sensitive flow-based suppression assay, we observed that both memory and naïve CD4+CD25-FOXP3- T-cells developed regulatory ability following a variety of activating stimuli. This suppressive ability was not due to competition for nutrients or antigen presenting cells. Interestingly, memory T-cells displayed significantly greater FOXP3 induction compared to naïve counterparts, and this phenotype correlated to significantly enhanced suppressive function. Furthermore, acquisition of suppressive ability in both the memory and naïve iTreg compartments was proportional to the strength of activating stimulus. While blockade of activation using anti-IL-2, CTLA-4 Ig, anti-TGF-B, indomethacin or cyclosporin A did not affect iTreg generation, methotrexate drastically preempted the induction of regulatory ability. Moreover, irradiation of iTregs also abrogated regulatory function. These studies suggest that iTreg development and function may vary dependent on precursor origin and emphasize the importance of characterizing the iTreg compartment prior to therapeutic application.