Donor Ceacam1 2/2 CD8 T cells express higher levels of integrin a 4 b 7 post-transplant Next, we studied a variety of possible mechanisms by which Ceacam1 may regulate donor T cell function. We analyzed donor WT and Ceacam1 2/2 alloactivated splenic T cells on day 14 after allo-BMT for trafficking molecules, and found that Ceacam1 2/2 CD8 + CD44 + CD62L 2 effector T cells expressed higher levels of integrin b 7 subunit and the gut homing integrin a 4 b 7 ( Figure 5A) , which is important for intestinal GVHD [31, 32, 33] . However, WT vs. Ceacam12/2 CD4 effector T cells had similar integrin b 7 subunit expression, yet also accumulated in greater numbers in the gut ( Figure 3A) , suggesting that regulation of target organ damage by Ceacam1 is very likely to involve multiple additional mechanisms beyond trafficking molecule expression. Additionally, levels of the a E subunit, which forms integrin a E b 7 , were similar, as were levels of CCR9, CD31, PSGL1, CCR7, CXCR3, and LFA1 (data not shown).