ILC2s navigate tissue redistribution during infection using stage-specific S1P receptors.

ABSTRACT

Lymphocytes can circulate as well as take residence within tissues. While the mechanisms by which circulating populations are recruited to infection sites have been extensively characterized, the molecular basis for the recirculation of tissue-resident cells is less understood. Here, we show that helminth infection- or IL-25-induced redistribution of intestinal group 2 innate lymphoid cells (ILC2s) requires access to the lymphatic vessel network. Although the secondary lymphoid structure is an essential signal hub for adaptive lymphocyte differentiation and dispatch, it is redundant for ILC2 migration and effector function. Upon IL-25 stimulation, a dramatic change in epigenetic landscape occurs in intestinal ILC2s, leading to the expression of sphingosine-1-phosphate receptors (S1PRs). Among the various S1PRs, we found that S1PR5 is critical for ILC2 exit from intestinal tissue to lymph. By contrast, S1PR1 plays a dominant role in ILC2 egress from mesenteric lymph nodes to blood circulation and then to distal tissues including the lung where the redistributed ILC2s contribute to tissue repair. The requirement of two S1PRs for ILC2 migration is largely due to the dynamic expression of the tissue-retention marker CD69, which mediates S1PR1 internalization. Thus, our study demonstrates a stage-specific requirement of different S1P receptors for ILC2 redistribution during infection. We therefore propose a fundamental paradigm that innate and adaptive lymphocytes utilize a shared vascular network frame and specialized navigation cues for migration.