Enhanced mRNA expression of Th1 cytokines and IL-12 in active pulmonary sarcoidosis

Background and aim of the work: Active sarcoidosis is considered to be a Th1 dominant condition. We examined whether Th1 cytokines are highly expressed at inflammed lesions of Japanese patients with sarcoidosis. Methods: To investigate the mRNA expression of Th1 cytokines and IL-12 in sarcoid BAL cells, we used semiquantitative reverse transcription - polymerase chain reaction method. Results: The mRNA expressions of Th1 cytokines (IFN-gamma and IL-2) in active sarcoid BAL cells were significantly elevated as compared with those in healthy volunteers. The proportion of positive IL-4 mRNA expression in sarcoid BAL cells was not significantly higher than that in healthy volunteers. Further, there was no significant difference in IFN-gamma mRNA levels between the groups positive and negative for IL-4 mRNA expression. Although the proportion of positive expression of IL-12 mRNA in active sarcoid BAL cells was not significantly higher than that in healthy volunteers, the group positive for IL-12 mRNA expression had significantly elevated levels of IFN-gamma mRNA than did the negative group. Conclusions: These results may indicate that IL-12 induces IFN-gamma expression and subsequent Th1 dominant condition in Japanese patients with sarcoidosis.