IL34 and graft versus host disease: Although we cannot conclude on a direct effect of IL-34 on Tregs in this experiment, since human IL-34 does not cross-react on murine cells and can only act on human cells and since in this model of humanized mice, GVHD is mediated mostly by T cells, this suggests a direct effect of IL-34 on Tregs and will need to be the subject of further investigations.