DISSOCIATION OF SPECIFIC AND TOTAL IGE ANTIBODY-RESPONSES FOLLOWING REPEATED LOW-LEVEL INFECTIONS WITH NIPPOSTRONGYLUS-BRASILIENSIS IN RATS

IgE, IgG and mast cell responses were studied in rats infected weekly with 10 larvae of Nippostrongylus brasiliensis (NB). Worm recovery at 8 weeks of repeated infections was six-fold greater than that of a sin gle infection with 10 larvae, suggesting the accumulation of worms dur ing the repeated infections. Total serum IgE was increased after 2 wee ks of infection, and further increased after repeated infections: at 6 weeks of infection the level was four to six times higher than that a fter a single infection. Anti-NB IgG1 levels were also significantly h igher after repeated infections than after a single infection. On the other hand, there was no significant difference in the level of anti-N B IgE between single and repeated infections, as determined by ELISA, as well as by passive cutaneous anaphylaxis (PCA) reaction. Mastocytos is was induced in the small intestine after both single and repeated i nfections, but the levels did not differ between the two. These result s indicate that total IgE and specific IgG1 production are augmented b y repeated helminth infections, but specific IgE and mast cell respons es are not. This pattern of response may minimize the development of I gE-dependent hypersensitivity reactions with repeated helminth infecti ons.