Interleukin 12 production by monocytes from patients with psoriasis and its inhibition by ciclosporin A

BACKGROUND: Psoriasis is a T-helper (Th)1 cytokine-mediated chronic skin disease and interleukin (IL)-12 has been shown to play a major role in the development of Th1 responses. OBJECTIVES: To elucidate the role of IL-12 in the pathogenesis of psoriasis and to study the effect of ciclosporin A (CsA) on Th1 deviation of this disease. PATIENTS/METHODS: We investigated IL-12 production by stimulated monocytes from patients with psoriasis who were treated with or without CsA. Monocytes were stimulated with interferon-gamma plus lipopolysaccharide (LPS) or Staphylococcus aureus Cowan strain I (SAC). The amount of IL-12 p70 produced by stimulated monocytes was evaluated by enzyme-linked immunosorbent assay. RESULTS: Compared with those from normal controls, LPS- but not SAC-stimulated monocytes from patients with psoriasis produced significantly higher amounts of IL-12. Interestingly, LPS-stimulated monocytes from patients with psoriasis treated with CsA produced significantly decreased amounts of IL-12 compared with those patients not treated with CsA. CONCLUSIONS: Our results suggest that IL-12 production by monocytes may have a critical role in the pathogenesis of psoriasis, and that the therapeutic effect of CsA on psoriasis may be achieved by correcting the deviation of the Th1/Th2 balance.