Cytokine-inducing activity of family 2 cystatins

Cystatins are physiological cysteine proteinase inhibitors. Here we report a novel function for some family 2 cystatins that is not related to these a ctivities. The release of interleukin-6 (IL-6) and interleukin-8 (IL-8) by the gingival fibroblasts and that of IL-6 by murine splenocytes were measur ed using ELISA systems specific for these cytokine molecules. Family 2 cyst atins, including cystatins C, SA1, SA2, S, and egg white cystatin, upregula ted the IL-6 production by two human gingival fibroblast cell lines or muri ne splenocytes and also the IL-8 production by gingival fibroblasts at phys iological concentrations. After complete saturation with papain, those fami ly 2 cystatins still upregulated IL-6 production, suggesting that the papai n-inhibitory site was not involved in the cytokine-inducing activity.