Circulating IL-12 p40 is increased in the patients with sarcoidosis, correlation with clinical markers.

Objective: Sarcoidosis is considered to be provocated by highly activated Th1 lymphocytes. Because interleukin 12 (IL-12) is one of the most important cytokines for promoting Th1 reaction, we tried to detect IL-12 and its ligand IL-12 receptor in sarcoidosis patients.

Patients And Methods: We measured the serum concentration of IL -12 p40 and IL-12 p70 by ELISA method with serum obtained from 60 sarcoidosis patients, and compared the serum concentration of IL-12 p40 with other clinical markers of disease activity. Next, we examined mRNA production of IL-12 p35, IL-12 p40, IL-12Rbeta1, and IL-12beta2 of sarcoid lymph nodes with semi-quantitative RT-PCR method.

Results: First, we showed that circulating IL-12 p40 was highly increased in sarcoidosis patients and was related to various other clinical markers. In particular, it was correlated with the number of involved organs which means systemic disease expansion. Second, we showed that the mRNA expression of IL-12 p40 and IL-12 receptor beta2 subunit was increased in sarcoid lymph nodes.

Conclusion: Our data suggest that increased circulating IL-12 p40 is an important systemic marker for disease activity, and it reflects the increased interaction between Il-12 and its ligand IL-12R in sarcoid lesions of involved organs.