Some Ceacam1 isoforms contain intracellular ITIM motifs, and activation of Ceacam1 results in the recruitment of the SHP-1 and SHP-2 phosphatases [8, 14] , which dephosphorylate substrates across a range of signaling pathways. Ceacam1 thus inhibits T cell receptor (TCR) signaling and suppresses multiple aspects of T cell function. Ceacam1 agonists attenuate cytokine secretion, T cell polarization and cytolytic function. In vivo, ligation of Ceacam1 with soluble ligands or over-expression of ITIM-containing Ceacam1 isoforms on T cells attenuates experimental colitis [7, 8] . Additionally, Ceacam1 is also expressed on intestinal T cells in patients with Celiac disease [15] and ulcerative colitis [16] , and may represent an attempt by the immune system to negatively regulate these inflammatory processes.