Here we analyzed the effect of CXCL12 exposure on naïve CD4 + T lymphocytes purified from peripheral blood by immunomagnetic negative isolation and cultured in a nutrient poor medium. We also studied, mainly by western blot analysis, the signaling pathways involved in CXCL12 action on naïve CD4 + T lymphocytes.
We found that CXCL12-exposed cells survived longer than untreated ones and this prolonged lifespan was specific for resting naïve lymphocytes, while in vitro activated lymphoblasts died rapidly despite CXCL12 treatment. We demonstrated that the increased percentage of living cells observed upon CXCL12 administration was not due to induction of proliferation but to a prosurvival effect of this chemokine. Moreover, our data suggest that this prosurvival effect on naïve CD4 + T lymphocytes might likely be mediated by PKA-dependent CREB activation and consequent increased expression of the antiapoptotic factors Bcl2 and BclXl.
This newly reported activity of CXCL12 might contribute to the maintenance of the naïve T lymphocytes pool in vivo, which is needed to ensure a proper immune response to new antigens.