Formaldehyde enhances mite allergen-induced eosinophilic inflammation in the murine airway.

Formaldehyde (FA) irritates the skin, eyes, and respiratory system and is considered to be a typical air pollutant. We investigated the effects of FA on the manifestations of airway inflammation caused by a house-dust mite allergen (Der f). ICR mice were exposed to 0.5% FA mist once a week for 4 weeks. The mice were sensitized intraperitoneally with Der f and ALUM prior to FA exposure. After the last FA exposure, theywere instilled intratracheally with Der f. The airway inflammation was subsequently examined. The Der f-specific IgG1 and IgE in plasma as well as the asthma-relevant cytokines in the lungs were measured. We found an increase in the plasma IgG1 production of and in the expression of interleukin-5 (IL-5) and regulated on activation, normal T cell expressed, and presumably secreted (RANTES) in the lungs of mice treated with Der f. The FA exposure enhanced the manifestation ofthe histopathological changes caused by Der f. This observation corresponded to the enhancement of IL-5 and RANTES production. However, the antigen-specific IgG1 antibody did not increase. The IL-4 cytokine level induced by Der fwith or without FA was the same as that of the control. IL-2, granulocyte macrophage-colony stimulating factor (GM-CSF), and antigen-specific IgE were not detected. FA exposure enhanced the eosinophilic airway inflammation and the proliferation of goblet cells, which were induced by a mite allergen responsible for the increased local expression of IL-5 and RANTES.