Telomerase is involved in IL-7-mediated differential survival of naive and memory CD4+ T cells.

IL-7 plays an essential role in T cell maintenance and survival. The survival effect of IL-7 is thought to be mediated through regulation of Bcl2 family proteins. After a comparative analysis of IL-7-induced growth and cell death of human naive and memory CD4(+) T cells, we observed that more memory CD4(+) T cells underwent cell division and proceeded to apoptosis than naive cells in response to IL-7. However, IL-7-induced expressions of Bcl2 family members (Bcl2, Bcl-x(L), Bax, and Bad) were similar between naive and memory cells. Instead, we found that IL-7 induced higher levels of telomerase activity in naive cells than in memory cells, and the levels of IL-7-induced telomerase activity had a significant inverse correlation with cell death in CD4(+) T cells. Furthermore, we showed that reducing expression of telomerase reverse transcriptase and telomerase activity significantly increased cell death of IL-7-cultured CD4(+) T cells. Together, these findings demonstrate that telomerase is involved in IL-7-mediated differential survival of naive and memory CD4(+) T cells.