Background The possible participation of diesel exhaust inhalation during the fetal period in the elevation of IgE against pollen in postnatal life was investigated.

      Method
      The experiment was conducted using rat pups. Group I; exposed to clean air (Control). Group 2, 3; exposed to total or filtered diesel exhaust during the fetal period (Total-C-C, Filtered-C-C). Group 4, 5; exposed to total or filtered diesel exhaust during the suckling period (C-Total-C, C-Filtered-C). Group 6,7; exposed to total or filtered diesel exhaust during the weaning period (C-C-Total, C-C-Filtered). Total diesel engine exhaust contained 1.73 mg/m3 particulate matter and 0.79 ppm nitrogen dioxide; filtered exhaust contained the same gases as the total exhaust without particulate matter. Intraperitoneal injection of 5 mg crude cedar pollen was performed at 2-week intervals from the 49th day after birth.


      Results
      The mean IgE titers measured by the P-K reaction in the Control, Total-C-C, Filtered-C-C, C-Total-C, C-Filtered-C, C-C-Total and C-C-Filtered were 64.0 ± 2.7, 469.5 ± 1.6, 332.0 ± 1.7, 380.4 ± 1.7, 394.8 ± 1.7, 115.9 ± 1.3 and 57.0 ± 2.8 respectively after the fourth immunization. There were significant differences between Total-C-C, Filtered-C-C, C-Total-C, C-Filtered-C and Control (p < 0.01, p < 0.01, p < 0.05, p < 0.01, respectively). The mean IgE titers by ELISA were 0.47 ± 0.06, 0.79 ± 0.35, 0.86 ± 0.46, 0.80 ± 0.22, 0.56 ± 0.08, 0.46 ± 0.04 and 0.45 ± 0.03, respectively. IgE titers in Filtered-C-C and C-Total-C were significantly higher than in Control (p < 0.05 for each).


      Conclusions
      Inhalation of diesel exhaust during differentiation of the immune system accelerated the elevation of IgE against pollen.