Earlier published work and our current study established that CD8+CD122+ Treg are the major population that undergoes lymphopenia-driven proliferation. They may also serve a regulatory function and prevent the

development of dangerous self-reactive T cells in the lymphodepleted mice and in the mouse models of EAE and Graves’ hyperthyroidism 20, 30–32. Recent studies demonstrated BGJ398 clinical trial the key role of IL-10 produced by CD8+CD122+ Treg in their suppressive function 32–34. The role of IL-10 in our model needs to be determined. In lymphoreplete mice, CD8+CD122+ Treg and CD4+CD25+ Treg are maintained primarily by IL-15 produced by DC 35 and IL-2 produced by naïve CD4+ T cells, respectively 36. Our data indicate that both IL-7 and IL-15 are required for the maximum proliferation of CD8+CD122+ Treg in lymphodepleted mice (Supporting Information Fig. 3). Only overexpression of IL-7 but not the normal levels of IL-7 found in IL-15-deficient mice could rescue CD8+CD122+ Treg, strongly suggesting these

Treg could act as a cytokine sink in lymphodepleted mice 37, 38. Recently, it was found that CD8+CD122+ T cells with innate function are enriched in mice lacking the IL-2-inducible T-cell kinase and primarily selected by on hematopoietic cells in thymus 39–44. The innate T cells shared same memory T-cell markers with CD8+CD122+ Treg; however, it remains to be determined whether Small molecule library order they are functionally similar to NKT cells, i.e. they could play a dual role in both innate immunity and as Treg. Our study

did not differentiate these cells from among all CD122+ T cells. A caveat of our study pertains to the face we relied on the co-transfer of competing cell populations rather than the depletion of endogenous CD122+ cells in a replete host – it was proved to be impossible to deplete endogenous CD122+ cells without affecting expanded pmel-1 T cells that acquired Methocarbamol CD122 after activation. Nevertheless, our results do suggest that regulatory CD8+ cells impede the response of tumor reactive cells by competition for limiting cytokines (especially IL-7). Another interesting observation is that depletion of CD122+ cells from spleen cells co-transferred with pmel-1 cells showed a dramatic effect on tumor growth (Fig. 3C). However, depletion of CD122+ cells increased the number of pmel-1 cells only at the peak of expansion (2 wk after tumor inoculation); no significant difference of pmel-1 cell number was observed at 3–4 wk after tumor inoculation (Fig. 1A), when tumor growth was most critically affected (Fig. 1C). This result indicates that there was not only a quantitative change but also some qualitative change that occurred in pmel-1 cells, which was caused by the depletion of CD122+ cells.