Effects of anti-IgE monoclonal antibody on a primary infection ofStrongyloides ratti in mice

Abstract

Many helminth infections induce profound changes in the immune response of the host. Enhancement of IgE production is one of the characteristic features observed during and after the course of infections. In Strongyloides ratti infection, IgE antibodies have been detected in mice (Dawkins et al. 1982) and in rats (Korenaga et al. 1986). Furthermore, we have shown that multiple infections with infective larvae of S. ratti depress parasitespecific IgE antibody production in rats (Korenaga et al. 1986). Intestinal mast cells have been suggested to be one of the effectors involved in the process of adult worm rejection from the small intestine of mice (Nawa et al. 1985). An involvement of IgE antibodies, however, has not been confirmed in protective immunity in murine strongyloidiasis. In the present study we examined a possible protective role of IgE in mice infected with S. ratti. To clarify this, we used IgE-depleted BALB/c mice, which were injected intraperitoneally with 5 30 gg purified rat antimouse IgE monoclonal antibody (6HD5, IgG2a) twice a week, beginning on the day of their birth. Ageand sex-matched normal mice served as controls. In all experiments, 5-7 mice in each group were infected with 1,000 L3 of S. ratti maintained in our laboratory. Methods for the cultured and inoculation of larvae have previously been described (Tada et al. 1979). For monitoring of fecal larval output, fresh feces were collected individually, weighed, and suspended in 10times their weight of water. Fecal samples (50 gl) were examined under a microscope. Soluble antigen was prepared from the infective larvae according to the methods of Dawkins et al. (1982). Parasite-specific IgE antibody was determined by passive cutaneous anaphylaxis (PCA; Watanabe and Ovary 1977). As a challenge, 2.8 mg L3 antigen was given intravenously with 1 ml 1% Evans blue solution at 24 h after the intradermal injection of serum samples. Blue spots measuring >_ 5 mm in diameter indicated a positive reaction. An enzyme-linked immunosorbent assay (ELISA;