Gammadelta T cells in Crohn's disease: a new player in the disease pathogenesis?

Abstract

Crohn's disease (CD) is a chronic relapsing systemic disease affecting the gastrointestinal tract. An altered immune response to commensal intestinal bacteria takes place in genetically predisposed individuals, resulting in chronic inflammation in the gut. Several alterations in the innate immunity mechanisms have been described in recent years. Thus, the study of the immunological aspects of CD, specifically the role of lymphocytes, is a key element for understanding the pathogenesis of the disease. Gammadelta T cells (γδ T cells) constitute only a small proportion of the lymphocytes that circulate in the blood and peripheral organs and they are present mainly in the epithelia, where they can constitute up to 40% of intraepithelial lymphocytes (IEL) in the intestinal mucosa. Due to their lack of MHC restriction and their unique plasticity and immune regulating properties they are considered key cells in the first line of defense against infections and in wound healing in the gut. Although there is growing experimental and clinical evidence of their implication in inflammatory bowel disease (IBD), including CD, their clinical relevance is still unclear. In this review, we address the possible involvement of γδ T cells in the pathogenesis of CD, reviewing their role against infections and in inflammation and the current evidence suggesting their implication in CD, offering a novel potential target for immunotherapy in IBD.