CD200R1 and colitis: However, given the symmetry we observe in the decreased susceptibility to colitis in CD200tg mice, with increased susceptibility in CD200KO and CD200RKO mice, along with evidence that in vitro inflammatory cytokine production from colonic DCs and macrophages of both WT and CD200KO mice is attenuated by exogenous CD200Fc (Fig 3D), our data argue strongly that the CD200:CD200R axis plays a prominent role in regulating inflammatory DSS-induced acute colitis in mice.