PGP and enteritis: One of the most studied substrates of P-gp is glucocorticoids; in human patients with inflammatory bowel disease (IBD), the expression of P-gp in the peripheral T-lymphocytes, intra-epithelial lymphocytes, and lamina propria lymphocytes appears higher in individuals with enteritis unresponsive to steroids, rather than in those with steroid-responsive enteritis [14,16].