Levels of interleukin 12, a cytokine of type 1 helper T cells, are elevated in sera from patients with systemic sclerosis.
OBJECTIVE: To determine serum levels and spontaneous production by peripheral blood mononuclear cells (PBMC) of interleukin 12 (IL-12), a potent inducer of type 1 helper (Th1) T cells, in patients with systemic sclerosis (SSc). METHODS: Serum IL-12 levels and spontaneous production levels of IL-12 in culture supernatants from PBMC were examined by ELISA. Serum levels of IL-4, IL-6. IL-10, and IL-13 and production levels by PBMC of IL-6 and IL-10 were also examined by ELISA. Renal vascular damage was determined as a pulsatility index (PI) by color flow Doppler ultrasonography of kidneys. RESULTS: Serum IL-12 levels were significantly elevated in patients with SSc (n = 62) compared with healthy controls (n = 20). Similarly, spontaneous production levels of IL-12 by PBMC in patients with SSc (n = 47) were higher than those in controls (n = 20). Serum IL-12 levels did not correlate with serum levels of any Th2-type cytokines such as IL-4, IL-6, IL-10, and IL-13. However, spontaneous production levels of IL-10 by PBMC significantly correlated with serum IL-12 levels in patients. Patients with elevated serum IL-12 levels had the increased PI values more frequently than those with normal IL-12 levels. Further, serum levels of IL-12 and production levels of IL-12 by PBMC correlated significantly with the PI values in patients with SSc. CONCLUSION: These results suggest that the increased levels of IL-12 may relate to the activation of Th1 cells in SSc and that IL- 12 overproduction may be associated with renal vascular damage.