Sensitivity of passive cutaneous anaphylaxis in rats. II. Suppression of passive cutaneous anaphylactic reactions in rats infected with Nippostrongylus brasiliensis.

The sensitivity of passive cutaneous anaphylactic (PCA) reaction was examined in rats infected with the nematode parasite, Nippostrongylus brasiliensis (Nb). PCA reactions with anti-DNP IgE antibody were remarkably suppressed by Nb infection already 10 days after infection and persisted for at least 28 weeks. 10 days after infection, no anti-Nb IgE antibody was present in the sera of infected rats, whereas 18 or 28 weeks after infection, circulating anti-Nb IgE antibody was present. It was concluded that two different mechanisms might explain the suppression. 10 days after infection, nonspecific IgE induced by potentiated IgE production inhibited passive sensitization with anti-DNP IgE antibody by occupying the IgE receptors on mast cells, whereas 18 or 28 weeks after infection, the mast cell IgE receptors were occupied by IgE antibody specific for the Nb antigen. The reactivity through non-immunological processes (skin sensitivity to compound 48/80) was not modified by Nb infection at any time after infection.