It is generally accepted that parasite-specific IgE plays a crucial role in host defense against helminthic parasites. However, the role of high levels of nonspecific IgE in helminthic infections is still controversial. To investigate the role of nonspecific IgE in primary infections with P. westermani, the effect of anti-IgE mAb treatment on serum IgE, Fc epsilon RII/CD23 expression and worm burden in Paragonimus-infected mice were examined. In mice treated with anti-IgE antibody, the total IgE levels were not detectable (1 microgram/ml) throughout the experiment compared with untreated infected mice. The mean percentages of Fc epsilon RII/CD23 positive splenic B cells in anti-IgE treated mice (range: 20.3 - 30.5) were also decreased throughout the experiment compared with untreated infected mice (range: 35.7 - 44.4). Reduction of the total IgE and expression of Fc epsilon RII/CD23 on splenic B cells resulted in decreased worm burden six weeks post infection. These results suggest that high levels of nonspecific IgE in mice with primary infections of P. westermani play a harmful, rather than beneficial, role for the host, perhaps by interfering with CD23-dependent cellular pathways.
