Immune-mediated alteration in gut physiology and its role in host defence in nematode infection

Activation of the mucosal immune system of the gastrointestinal tract in nematode infection results in altered intestinal physiology, which includes changes in intestinal motility and mucus production. These changes are considered to be under direct immunological control rather than a non-specific consequence of the inflammatory reaction to the infective agent. However, little is known about the immunological basis for the changes in intestinal physiology accompanying nematode infection, or the precise role of these changes in host defence, which remains an important area to explore. In this review we describe the mechanisms by which the immune response to nematode infection influences the changes in two major cells of intestinal physiology, namely smooth muscle and goblet cells, and how these changes in intestinal physiology contribute to the host defence. Data clearly demonstrate that the T helper (Th) 2 type immune response generated by nematode infection plays an important role in the development of infection-induced intestinal muscle hypercontractility and goblet cell hyperplasia and that these immune-mediated changes in intestinal physiology are associated with worm expulsion. These observations strongly suggest that intestinal muscle contractility, goblet cell hyperplasia and worm expulsion share a common immunological basis and may be causally related. These data not only provide insights into host defence in nematode infection in the context of muscle function and goblet cell response, but also have broad implications in elucidating the pathophysiology of a wide range of gastrointestinal disorders associated with altered gut physiology.