CEACAM1 regulates CD8 T cell immunity and protects from severe pathology during induced colitis.

The incidence of gastrointestinal infections continues to increase, and infectious colitis contributes significantly to morbidity and mortality worldwide. Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) has been discovered to be strongly involved in the intestinal homeostasis. However, whether intestinal CEACAM1 expression has an impact on the control of infectious colitis remains elusive. is a gram-negative enteric pathogen that induces colonic inflammation in mice, with a critical role for CD4 T cell but not CD8 T cell immunity to primary infection. Here, we show that mice are much more susceptible to infection than wildtype mice, which is mediated by a defect in the intestinal barrier and, surprisingly, by a dysregulated CD8 T cell but not CD4 T cell response in the colon. CEACAM1 expression is essential for the control of CD8 T cell immunity, as CEACAM1 deficiency during infection inhibits CD8 T cell exhaustion. We conclude that CEACAM1 is an important regulator of CD8 T cell function in the colon, and blocking CEACAM1 signaling to activate CD8 T cells may have unforeseen side effects.