The impact of ageing on the intestinal epithelial barrier and immune system

•Ageing has a profound impact on both adaptive and innate mucosal immune responses.•Ageing compromises epithelial barrier integrity and its regulatory functions.•M (microfold) cell transport across the epithelium is reduced.•Immunoregulation is altered in the aged gut immune system.•Many basic aspects of intestinal immunity in ageing are still unknown. The vast mucosal surface of the intestine is patrolled by a large number of lymphocytes forming the intestinal immune system. Like any other system in the body, this branch of the immune system is affected by ageing. Although our knowledge on the age-associated changes of the systemic immune system has improved over the past few years, our understanding of the mechanisms of senescence of both adaptive and innate immune system of the gastrointestinal (GI) tract is still largely incomplete. However, recent advances in the field have shown that the identification of the events underlying the ageing process in the gut may have important consequences on health and wellbeing far beyond the GI-tract. The aim of this review is to summarise the impact of ageing on the intestinal immune system, including the gut epithelium and other components of the intestinal barrier that maintain intestinal immune homeostasis and shape antigen-specific immune responses.