It was reported that reconstitution of syngeneic, naïve (CD45RBhi or CD62L+CD44-) CD4 T cells in these lymphopenic mice causes an oligoclonal expansion of effector CD4 T cells and colitis development due to their cross-reactivities with endogenous antigens, including self-antigens and gut microflora (20, 21). Here, SELL is linked to colitis.