Inflammatory bowel diseases Crohn's disease and ulcerative colitis are complex multifactorial diseases that involve the interaction between innate and adaptive immunity. TNF-α is a potent proinflammatory cytokine with pleiotrophic effects on cells of the innate and adaptive immune system. Medical therapies that block TNF have changed the clinical management of inflammatory bowel disease. This review will discuss the new recommendations for the use of anti-TNF agents in the treatment of inflammatory bowel disease, as well as insights into immunogenicity and the safety of these agents. In addition, new biologic therapies that inhibit various elements in the leukocyte infiltration process and others that target proinflammatory cytokines will be addressed. This review will cover key studies examining the use of biologic agents in the treatment of Crohn's disease and ulcerative colitis.