We observed that recipients of Ceacam1 2/2 T cells had more severe large intestinal GVHD (Figure 2A) . Surprisingly however, these mice exhibited less thymic GVHD, as determined by thymic cellularity and numbers of CD4 + CD8 + double-positive (DP) thymocytes ( Figure 2 ). Thymic cellularity from age/sex-matched non-transplanted animals are shown in Figure S2 . We also observed a modest trend towards less skin GVHD in recipients of Ceacam1 2/2 T cells ( Figure 2C ), suggesting that Ceacam1 2/2 T cells caused preferential damage to the (large) intestines.