Influence of environmental mite antigen on anti-mite antibody production in mice

To investigate the effects of environmental mite antigen on anti-mite antibody production in mice, a mite-free breeding system was established. The amount of Dermatophagoides farinae (Df) antigen was measured using the ELISA inhibition method. Df antigen was detected in the wood-chip bedding used in our conventional breeding system for 1 week (2.55 +/- 0.79 micrograms/g sample) and 2 weeks (8.96 +/- 3.27 micrograms/g sample). Df antigen was also detected in the standard diet (0.4 micrograms/g sample) in the conventional system, whereas no antigen was detected in the case of the mite-free breeding system. Neither anti-Df IgE nor IgG antibody was detected before immunization, either in mice raised in the mite-free breeding system or in mice raised in the conventional system. Primary and secondary antibody production after immunizations with 1 or 10 micrograms Df antigen was studied in the mouse bred in the conventional and in the mite-free breeding system. Primary anti-Df IgE antibody response of the conventional group was greater than that in the mite-free group after immunization with either dose of 1 and 10 micrograms Df antigen. Primary anti-Df IgG antibody response was greater in the conventional than the mite-free group after immunization with 1 microgram Df antigen. Secondary IgE and IgG responses of the conventional group were greater than the mite-free group after immunizations with 10 micrograms Df antigen. These results suggest that anti-Df antibody production is enhanced by chronic exposure to Df antigen in the environment.