The value of interleukin-12 as an activity marker of pulmonary sarcoidosis.

Sarcoidosis is characterized by hyperactivity of T-helper lymphocytes and recent studies showed that they were mainly Th1 cells. IL-12 is a major cytokine inducing Th1 differentiation of naive T cells. This study was performed to test whether IL-12 can be a marker for disease activity and possibly a prognosis in sarcoidosis.IL-12 levels of BALF (BALF-IL-12) and conditioned medium of alveolar macrophages (AM) were measured by ELISA in 36 patients with pulmonary sarcoidosis (14 males and 22 females, mean age: 39.6 +/- 11.0 years) and eleven normal controls. Clinically, 16 patients had active sarcoidosis and 20 had an inactive disease.BALF-IL-12 of sarcoidosis patients (41.3 +/- 43.9 pg/ml) was significantly higher than that of normal controls (2.5 +/- 0.4 pg/ml) (p < 0.001). The patients with active disease (71.3 +/- 54.3 pg/ml) had a higher BAL-IL-12 level than those with inactive disease (17.3 +/- 13.8 pg/ml) (p = 0.0001). It had a significant correlation with the number of T4 cells (p = 0.0001), total cell number, number and percentage of lymphocytes (p = 0.0001) and AM (p = 0.001) in BALF. It was also significantly correlated with soluble ICAM-1 levels in serum (p = 0.0001) and BALF (p = 0.002), and ICAM-1 expression of AM (p = 0.001). Furthermore the patients whose condition worsened without therapy had a significantly higher initial BALF-IL-12 level than the patients whose condition improved spontaneously. The AM of sarcoidosis secreted significantly more IL-12 (133 +/- 177 pg/ml) than AM of controls (68.3 +/- 43.7 pg/ml) (p = 0.038).Our data suggest that the BALF-IL-12 level can be used as a marker of the activity of pulmonary sarcoidosis and possibly prognosis.