Rat strain difference in histology and expression of Th1- and Th2-related cytokines in nasal mucosa after short-term formaldehyde inhalation.

Changes in histology and Th1- and Th2-related cytokines expression in nasal mucosa were examined in Brown Norway (BN) and Fischer 344 (F344) rats after 5-day inhalation of 1% formaldehyde aerosol. In F344 rats, mucosal lesions characterized by degeneration and/or desquamation of epithelial cells with neutrophil infiltration were observed at all levels of nasal cavity and all kinds of mucosal epithelia were involved in such lesions. In BN rats, mucosal lesions were milder and the olfactory epithelium was free from lesions. The levels of Th1-related cytokines (IFN-gamma and IL-2) were significantly depressed and those of Th2-related cytokines (IL-4 and IL-5) also tended to be depressed in BN rats. In F344 rats, similar but much less clear alterations in the levels of Th1- and Th2-related cytokines were observed. Such results of measurement of Th1- and Th2-related cytokines mRNAs seem to be interesting although their significance is still obscure.