Hypersensitivity reactions in small intestine. I Thymus dependence of experimental 'partial villous atrophy'.

Rats infected with the intestinal nematode Nippostrongylus brasiliensis have crypt hyperplasia with villous atrophy in affected areas of the small intestine. In thymus-deprived (B) rats the course of infection is prolonged but, despite the presence of many worms in the intestinal lumen, villi and crypts appear largely normal. This suggests that the tissue damaged associated with N. brasilliensis infection is caused, not by the worms, but by a local thymus-dependent immune reaction. There is some evidence to implicate lymphocytes rather than antibodies in this reaction. It is already know that T-cell-associated damage to the small intestine, such as occurs in allograft rejection, produces subtotal villous atrophy. The present findings suggest that when T cell react locally with helminth antigens a similar type of damage occurs. The presence of a local cell-mediated immune reaction may be the common factor which causes villous atrophy and crypt hyperplasia in many small intestinal diseases, eg, viral enteritis, giardiasis, cow's milk allergy, and coeliac disease.