CD4 and Crohn disease: There is increasing evidence from experimental mouse models and from clinical observations that angiogenesis is an important component of IBD pathogenesis.[24], [29] For example, VEGF has been shown to be elevated in distal colonic tissue in the CD4+CD45RBhigh colitis model [22] as well as in intestinal tissues and sera of patients with Crohn’s disease and ulcerative colitis [39]–[41].