PECAM1 and Crohn disease: Palatka et al. [25]reported an eNOS/CD31 ratio of 92% in healthy mucosal biopsies, whereas thisratio was 8% in tissue samples from patients with Crohn’s disease and 82% insamples from patients with ulcerative colitis, which suggests that eNOSactivity is diminished in disease-affected endothelial cells.