No abstract

Thymic commitment of human FOXP3 regulatory T cells begins at the double positive (DP) CD4 CD8 stage. In the current study we show that interleukin-2 promotes the development of FOXP3 thymocytes and enhances their survival at the DP phase. IL-2 increases the frequency of FOXP3 cells and promotes the Treg phenotype after TCR-mediated positive selection at the most mature DP stage. However, it has no effect on FOXP3 cells at the earlier maturation steps before positive selection. DP FOXP3 are highly susceptible to cell death but IL-2 promotes their survival. The anti-apoptotic protein BCL-2 (B Cell Lymphoma 2) is also upregulated by IL-2 at the most mature DP stage. In addition to IL-2, we identify IL-15 to have a significant role in the upregulating FOXP3 and survival of Tregs at the DP phase. IL-7 also increases the expression of BCL-2 in the DP FOXP3 thymocytes. Our results indicate that common gamma chain cytokines IL-2, IL-7 and IL-15 promote the development of regulatory T cells at the most mature DP stage after TCR-mediated positive selection through suppressing cell death. This article is protected by copyright. All rights reserved.

Background The number of mutations in cancer cells is an important predictor of a positive response to cancer immunotherapy. It has been suggested that the neoantigens produced by these mutations are more immunogenic than nonmutated tumor antigens, which are likely to be protected by immunological tolerance. However, the mechanisms of tolerance as regards tumor antigens are incompletely understood. Methods Here, we have analyzed the impact of thymic negative selection on shared T‐cell receptor (TCR) repertoire associated with the recognition of either mutated or nonmutated tumor antigens by comparing previously known TCR—antigen—pairs to TCR repertoires of 21 immunologically healthy individuals. Results Our results show that TCRα chains associated with either type of tumor antigens are readily generated in the thymus, at a frequency similar to TCRα chains associated with nonself. In the peripheral repertoire, the relative clone size of nonself‐associated chains is higher than that of the tumor antigens, but importantly, there is no difference between TCRα chains associated with mutated or nonmutated tumor antigens. Conclusion This suggests that the tolerance mechanisms protecting nonmutated tumor antigens are non‐deletional and therefore potentially reversible. As unmutated antigens are, unlike mutations, shared by a large number of patients, they may offer advantages in designing immunological approaches to cancer treatment.