Interleukin 10 receptor, beta subunit (IL10RB/IL-10RB) also known as Cytokine receptor family 2 member 4, Interleukin-10 receptor subunit 2, and cytokine receptor family II, member 4, is a subunit for the interleukin-10 receptor. IL10RB/IL-10RB belongs to the cytokine receptor family. It is an accessory chain essential for the active interleukin 10 receptor complex. Coexpression of this and IL10RA proteins is required for IL10-induced signal transduction. Defects in IL10RB/IL-10RB are the cause of inflammatory bowel disease type 25 (IBD25). It is a chronic, relapsing inflammation of the gastrointestinal tract with a complex etiology. It is subdivided into Crohn's disease and ulcerative colitis phenotypes. Crohn's disease may affect any part of the gastrointestinal tract from the mouth to the anus, but most frequently it involves the terminal ileum and colon. Bowel inflammation is transmural and discontinuous; it may contain granulomas or be associated with intestinal or perianal fistulas. In contrast, in ulcerative colitis, the inflammation is continuous and limited to rectal and colonic mucosal layers; fistulas and granulomas are not observed. Both diseases include extraintestinal inflammation of the skin, eyes, or joints.