Brugia pahangi: immunologic evaluation of the differential susceptibility of filarial infection in inbred Lewis rats

After inoculating inbred Lewis rats with infective larvae of Brugia pahangi, we found consistently that patent infection was established in only about two-thirds of experimental animals. To determine which aspects of the host response were responsible for this differential susceptibility to infection, we evaluated all animals with respect to blood leukocyte levels, antifilarial IgG and IgE antibody production, and specific lymphocyte responses to mitogens and filarial antigens during the first 50 weeks of infection. In the critical “prepatent” period of infection, each of these responses developed in an essentially identical fashion in the infected and resistant groups except for the production of specific IgE antibodies. While those animals destined to resist infection developed specific IgE antibodies between Weeks 5 and 8, none of the animals that became microfilaremic showed a similar IgE response. These findings suggest that the development of specific IgE antibodies played a role in protecting the animals from acquiring filarial infection.