DIESEL EXHAUST PARTICLES BLOCK INDUCTION OF ORAL TOLERANCE IN MICE

We investigated the effect of diesel exhaust particles (DEP) on oral t olerance. Oral tolerance was induced by feeding mice with 10 mg of hen egg lysozyme (HEL) daily over a period of 5 days before immunization with the antigen. Varying doses of DEP were orally administered immedi ately before each feeding of HEL. The results showed that oral adminis tration of HEL significantly suppressed production of anti-MEL IgG, Ig G1 and IgG2a antibodies, delayed-type hypersensitivity and proliferati ve responses of lymph node cells to the antigen. The suppression of th ese immune responses to HEL by the oral antigen was associated with a marked decrease in secretion of interferon-gamma and interleukin-4 fro m the lymphoid cells. Administration of DEP dose-dependently blocked s uppression by oral HEL of antigen-specific IgG, IgG1 and IgG2a antibod y production, delayed-type hypersensitivity and lymphoid cell prolifer ation. The suppression by the fed antigen of secretion of interferon-g amma and interleukin-4 was also markedly diminished by the particles. Thus, DEP appear to be effective in blocking induction of oral toleran ce.