Enhancement of collagen-induced arthritis in mice by diesel exhaust particles

The present study was undertaken to investigate the effect of diesel exhaust particles (DEP) on collagen-induced arthritis (CIA), which is an experimental model of autoimmune disease, in mice. CIA was induced by s.c. injection of type II collagen (CII) emulsified with complete Freund's adjuvant into the base of the tail (day 0) followed by a booster injection on day 21. Varying doses of DEP were intranasally administered every 2 days from days 0 to 20. The results showed that administration of DEP enhanced both the incidence and the severity of CIA. The enhancement of the disease was associated with pronounced production of anti-CII IgG and IgG2a antibodies. Treatment with DEP also augmented proliferative responses of spleen cells to CII. There was marked secretion of interferon-gamma, interleukin (IL)-2, and IL-4 from the lymphoid cells in DEP-treated mice. Administration of DEP after onset of CIA was also effective in enhancing the severity of the disease as well as production of anti-CII IgG and IgG2a antibodies and secretion of interferon-gamma, IL-2, and IL-4. These results suggest that exposure to DEP may influence autoimmune disease.