Psoriatic fibroblasts secrete lower amounts of IL-6 than healthy fibroblasts before and after stimulation with TNF-alpha

Altered function of the fibroblasts is thought to contribute to the pathoge nesis of psoriasis, To further elucidate this point, we compared the abilit y of fibroblasts from psoriatic lesions and of fibroblasts from healthy ind ividuals to produce interleukin-6 (IL-6), The IL-6 levels were measured by ELISA in serum-free culture medium before and after stimulation of monolaye r fibroblasts with various concentrations of tumour necrosis factor-alpha ( TNF-alpha), platelet-derived growth factor (PDGF), and interferon-gamma (IF N-gamma), alone and in different combinations. The production of IL-6 in th e fibroblast cultures was stimulated by TNF-alpha (0.01-10 nm/ml medium) in a dose-dependent way. Fibroblasts from psoriatic lesions produced lower am ounts of IL-6 than fibroblasts from healthy individuals both before and aft er stimulation with the different concentrations of TNF-alpha (P = 0.012), The ratios between the IL-6 concentrations before and after stimulation wit h TNF-alpha were similar in both types of fibroblasts, indicating that the capacity to produce IL-6 is reduced in psoriatic fibroblasts compared with healthy ones. The production of IL-6 was not influenced by either PDGF or I FN-gamma, These findings support the view that the phenotype of the fibrobl ast is altered in psoriasis.