Immunological consequences of intestinal helminth infections in C57BL mice. Humoral responses to polyvinyl pyrrolidone.

Infection with Trichuris muris eggs or Nematospiroides dubius larvae (orally administered) did not affect IgG or IgM antibody responses to 0 X 2 micrograms polyvinyl pyrrolidone (PVP) (intravenously (i.v.) or intraperitoneally (i.p.)) or 20 micrograms PVP (i.p.) in C57BL mice. However, Nippostrongylus brasiliensis L3 subcutaneously (s.c.) and N. dubius L3 (i.v.) significantly increased responses to PVP (i.p.) so migrating larvae are probably responsible. Similar enhancement was obtained when extracts of N. brasiliensis worms or N. dubius larvae were administered i.p. The activity of N. brasiliensis extract was trypsin-insensitive and unaffected by heat (1 h, 60 degrees). Extracts of A. suum did not cause significant enhancement and BALB/c mice were not affected by N. brasiliensis extract. The possible roles of regulatory T-cells, non-specific mitogenesis and macrophage activation are discussed.