Induction of systemic Th1 and Th2 immune responses by oral administration of soluble antigen and diesel exhaust particles

The present study was undertaken to examine whether oral administration of soluble antigen together with diesel exhaust particles (DEP) induced the systemic immune response in mice. Mice were orally given 1 mg of hen egg lysozyme (HEL) with varying doses of DEP every 3 days over a period of 15 days. The results showed that oral administration of HEL plus DEP produced anti-MEL IgG antibodies in serum in a dose-related fashion, while either HEL or DEP alone failed to show the antigen-specific IgG antibody production. Production of anti-MEL IgG2a and IgG1 antibodies, which are dependent on Th1 and Th2 CD4(+) T cells, respectively, was seen in mice fed with combined HEL and DEP, although anti-MEL IgG1 antibodies appeared to be more efficiently produced by lower doses of DEP than anti-MEL IgG2a antibodies. There was marked antigen-specific proliferation of spleen cells in mice treated with MEL and DEP. The anti-MEL antibody production and lymphoid cell proliferation to the antigen were associated with marked secretion of the Th1 cytokine IFN-gamma as well as the Th2 cytokine IL-4. These results suggest that DEP may act as a mucosal adjuvant in the gut enhancing systemic Th1 and Th2 immune responses and might play a role in oral immunization and food allergy. (C) 1999 Academic Press.