Kinetics and Isotype Distribution of Parasite-Specific Antibody Responses in the Spleen of Mice during Primary Infection with <i>Schistosoma mansoni</i>

Abstract

The solid-phase enzyme-linked immunospot assay has been adapted for enumerating cells secreting antibodies to crude antigenic extracts from the main developmental stages of Schistosoma mansoni. The frequencies of splenocytes secreting antibodies reactive with soluble antigenic extracts from cercariae, adult worms, and eggs, were examined in C57BL/6 mice during the first 12 weeks of a primary infection with S. mansoni. Despite the existence of cross-reactive moieties present in these antigenic preparations, the characteristics of the responses monitored differed with regard to kinetics, magnitude, and/or isotype distribution. The responses peaked between 8 and 10 weeks of infection, were characterized by a predominance of cells secreting IgM antibodies against all three antigens, and followed the patterns IgM greater than IgA greater than IgG for cercariae, IgM greater than IgG greater than IgA for adult worms and IgM greater than IgG greater than IgA for egg extracts. On the other hand, these patterns were not always reflected in serum, especially for cercariae-reactive circulating IgG and IgA responses. When examined for numbers of total IgM-, IgG- and IgA-producing cells, the spleen of S. mansoni-infected mice was shown to display considerable numbers of immunoglobulin-producing cells in all three isotypes studied. The most spectacular increases were noted for IgG-secreting cells (more than 10-fold) and for IgM-secreting cells (up to 6-fold) 4 weeks after initial cercarial exposure. Taken together, these observations indicate that primary infection with S. mansoni results in early immunoregulatory alterations which may contribute to the maintenance of specific as well as nonspecific B cell hyperactivity.(ABSTRACT TRUNCATED AT 250 WORDS)