Innate lymphoid cells lacking surface expression of CD90 are functional
ABSTRACTHuge progress has been made in understanding the biology of innate lymphoid cells (ILC) by adopting several well-known concepts of T cell biology. As such flow cytometry gating strategies and markers, such as CD90, to identify ILC were discovered. Here we report that most non-NK intestinal ILC have a high expression of CD90 as expected, but surprisingly some have only a low or even no expression of this marker. CD90-negative CD127+ ILC were identified among all ILC subsets in the gut. CD90-negative cLP ILC2 were frequent at steady state. The frequency of CD90-negative CD127+ ILC was dependent on stimulatory cues in vitro and in vivo, and CD90-negative CD127+ ILC played a functional role as a source of IL-13, IFNγ and IL-17A at steady state and upon dextran sulphate sodium-elicited colitis. Hence, this study highlights for the first time that CD90 is not constitutively expressed by functional ILC in the gut.