Immunoglobulin class specific responses to biochemically defined antigens of Trichinella spiralis

A comparison of the humoral response to resistant (NIH) and susceptible (C3H) strains of mice, which reject adult worms at different rates during a primary infection, was made following infection with Trichinella spiralis. The serum concentration of immunoglobulins of the heavy chain classes IgM, IgG1, IgG2, IgG3 and IgA were determined by single radial immunodiffusion. Antibodies of the same immunoglobulin isotypes to biochemically defined, stage specific surface and secreted components of three stages of parasite development were also determined using an isotype specific immuno-coprecipitation assay. Independent variation of the responses of each immunoglobulin isotype was observed. The specific anti-parasite response did not reflect total serum immunoglobulin levels in all immunoglobulin classes, and this is discussed in relation to basic mechanisms of immunoglobulin class switching. Finally a close correlation was observed in resistant (NIH) mice between the production of IgA antibody to surface components of adult worms and accelerated expulsion of this stage of the worm from the gastrointestinal tract. The possible relevance of this IgA response is further indicated by the failure of susceptible mice to synthesise IgA antibodies to the same surface antigens.