MC5R and inflammatory bowel disease: Also, there is the emerging role of the melanocortin system, particularly the melanocortin-3 receptor (MC3R) and melanocortin-5 receptor (MC5R), critical regulators of immune activity through their interaction with α-melanocyte-stimulating hormone (α-MSH) and adrenocorticotropic hormone (ACTH), whose degree of expression in the colons of IBD patients points to a possible correlation with the degree of disease activity [10].