Shinohara and colleagues report that only IL-7R+CD4+ T cells (and not NK cells, granulocytes, DCs, or macrophages) contribute to colitis in their adoptive transfer model [20], whereas von Freeden-Jeffry and colleagues reported that in the absence of T and B cells, IL-7 dramatically increases F4/80+ cell infiltration into the intestinal mucosa upon H. hepaticus infection resulting in chronic intestinal inflammation [8]. The gene discussed is CD4; the disease is inflammation.