CEACAM1 and graft versus host disease: In our model systems, WT T cells in a Ceacam1-deficient environment showed a phenotype similar to that of Ceacam1−/−alloactivated T cells: both showed increased activation, selective damage to the large intestines, and preferential accumulation in the MLN and intestinal parenchyma of mice with GVHD, and correspondingly decreased infiltration of the liver and PLN, ultimately leading to exacerbation of disease, with accelerated mortality in the first two weeks post-transplant.