Immunology

.... Although intranodal T cell migration is controlled in part by chemokines and LFA-1/ICAM-1, the mechanisms underlying their migratory activity independent of these factors remain to be elucidated. In this study, we show that LN stromal cells constitutively express autotaxin (ATX), an ectoenzyme that is important for the generation of lysophosphatidic acid (LPA). Importantly, CCL21+ stromal cells in the T zone produced and immobilized ATX on their cell surface. Two-photon imaging using LN tissue slices revealed that pharmacological inhibition of ATX or LPA receptors significantly reduced T cell migration, and this was further exacerbated by blockage of Gαi signaling or LFA-1. Therefore, T cell motility mediated by the ATX–LPA axis was independent of Gαi and LFA-1. LPA induced slow intermittent movement of T cells in vitro in a LFA-1–independent manner and enhanced CCL21-induced migration. Moreover, LPA and CCL21 cooperatively augmented RhoA activity in T cells, which was necessary for efficient intranodal T cell migration via the downstream ROCK–myosin II pathway. Taken together, T zone stromal cells control optimal migratory behavior of T cells via multiple signaling cues mediated by chemokines and ATX/LPA.