Interleukin‐13 stimulates interleukin‐6 production by human keratinocytes

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Abstract
Interleukin‐13 (IL‐13) is a recently described human lymphokine which is produced by activated T‐cells. Its effect on the production of IL‐6 by normal keratinocytes and keratinocyte cell lines of human origin was studied and compared to that of IL‐4. IL‐13, similarly to IL‐4, stimulated IL‐6 expression by these cells in a dose‐ and time‐dependent manner. Contamination with endotoxin was excluded by the use of polymyxin B and heat‐inactivated cytokines. Further, we showed that IL‐13, like IL‐4, not only stimulated IL‐6 production but also was able to induce overexpression of this cytokine in response to an inflammatory signal such as lipopolysaccharide (LPS). In a previous study, we demonstrated that IL‐13, by inhibiting IL‐6 and other cytokines produced by monocytes, exhibited an ‘anti‐inflammatory profile’ comparable to that displayed by IL‐4. In contrast, we show here that IL‐13, by stimulating IL‐6 production by keratinocytes, may favour the installation of an inflammatory process at a local level and, here again, it acted like IL‐4. Therefore, according to the type of target cell, these two ‘TH2 type’ cytokines induce similar opposing effects on IL‐6 production and are likely to be important cytokines in the regulation of inflammation at both systemic and local levels.