The immunological consequences of nematode infection

Nematode infections in the gut induce a strong immune response which is rapidly detected parenterally. The response is thymus-dependent and long-lasting and involves both antibodies and cell-mediated reactions. The immunological response to unrelated antigens, tumours and other infectious organisms is altered in animals infected with nematodes. Both antibodies and sensitized lymphocytes participate in the immune response which affects the nematodes themselves, and characteristically the lymphocyte-dependent step cannot act in lactating animals and is neither induced nor able to act in young animals. Present evidence suggests that, despite their well-known association with helminth infections, parasite rejection from the gut does not require the participation of IgE antibodies, mast cells or eosinophils. Homing of lymphoblasts from the mesenteric lymph node or thoracic duct lymph to the small intestine is increased in rats and mice infected with Nippostrongylus brasiliensis or Trichinella spiralis and the increase is antigenically non-specific. In mice infected with T. spiralis this increase is represented mainly by thymus-derived lymphoblasts.