Splenic stromal cells mediate IL‐7 independent adult lymphoid tissue inducer cell survival

Lymphoid tissue inducer cells (LTi) play an important role in the development of lymphoid tissue in embryos. Adult CD4+CD3− LTi‐like cells present a similar phenotype and gene expression to their embryonic counterpart and have important roles in CD4+ T‐cell memory and lymphoid tissue recovery following viral infection. However, adult LTi‐like cells are heterogeneous populations and the factors that regulate their survival and accumulation within secondary lymphoid organs remain unclear, in particular whether the T‐zone stroma is involved. Here we report the identification and characterization of a distinct subset of podoplanin+ murine splenic stromal cells that support adult LTi‐like cell survival. We have identified and isolated CD45−podoplanin+ stromal cell populations which have a similar but distinct phenotype to T‐zone reticular cells in LN. CD45−podoplanin+ fibroblast‐like cells mediate LTi‐like cell survival in vitro; surprisingly this was not dependent upon IL‐7 as revealed through blocking Ab experiments and studies using LTi‐like cells unable to respond to γ chain cytokines. Our findings show that adult LTi‐like cells require extrinsic signals from podoplanin+ splenic stromal cells to survive and suggest that IL‐7 is not necessary to mediate their survival in the adult spleen.