The article reports on the study of interferon-regulatory factor 4 (IRF4) as an essential regulator of interleukin-6 (IL-6) production by mucosal T cells. Neurath and colleagues examined the role of IRF4 by the use of three models of T-cell-dependent colitis in IRF4-deficient mice. The study revealed that IRF4 can mediate T-cell-dependent experimental colitis and had a therapeutic use for the inflammatory bowel diseases in humans.