Cutting edge: lymphoid tissue inducer cells maintain memory CD4 T cells within secondary lymphoid tissue

Abstract

Phylogeny shows that CD4 T cell memory and lymph nodes (LNs) co-evolved in placental mammals. In ontogeny, retinoic acid orphan receptor (ROR) γ-dependent lymphoid tissue inducer (LTi) cells program the development of mammalian LNs. Here, we show that while primary CD4 T cell expansion is normal in RORγ-deficient mice, the persistence of memory CD4 T cells is RORγ-dependent. Furthermore, using bone marrow chimeric mice we demonstrate that LTi cells are the key RORγ-expressing cell type sufficient for memory CD4 T cell survival in the absence of persistent antigen. This effect was specific for CD4 T cells, since memory CD8 T cells survived equally well in the presence or absence of LTi cells. These data demonstrate a novel role for LTi cells, archetypal members of the innate lymphoid cell family, in supporting memory CD4 T cell survival in vivo