IL-2 receptor chain cytokines differentially regulate human CD8+CD127+ and CD8+CD127- T cell division and susceptibility to apoptosis

Expression of IL-7 receptor alpha (CD127) is associated with naive and memory (i.e. non-effector) CD8+ T cell phenotypes. Effector CD8+ T cells are predominantly CD127- and most die by apoptosis. Therefore, CD127 appears to be a marker for CD8+ T cell differentiation, yet its role in CD8+ T cell survival and memory development is unclear. To address this, we investigated the cell death and cell division of isolated CD8+CD127+ and CD8+CD127- T cells in response to common IL-2 receptor gamma chain (gamma(C)) cytokines other than IL-7. We show here that (i) memory cells (CD127+CD45RA-) divide frequently in response to either IL-2, -4 or -15; (ii) IL-2 and -15 enhance cell division in effector-memory-like cells (CD127-CD45RA+) while IL-4 enhances the cell division of effector cells (CD127-CD45RA-); (iii) CD8+CD127+ T cells are more sensitive to the anti-apoptotic effects of IL-2 or IL-15 than CD8+CD127- T cells and (iv) CD8+CD127+ T cell produce more Bcl-2 in response to IL-2 or IL-15 compared with CD8+CD127- T cells. Therefore, CD8+CD127+ and CD8+CD127- T cells differ in their responsiveness to cell division and anti-apoptotic signals from IL-2, -4 and -15. This suggests a role for gamma(C) cytokines in the pathogenesis of diseases in which CD127 expression is altered on CD8+ T cells such as in progressive viral infections and cancer.