INTERLEUKIN-13 STIMULATES INTERLEUKIN-6 PRODUCTION BY HUMAN KERATINOCYTES

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 w as studied and compared to that of IL-4. IL-13, similarly to 1L-4, sti mulated IL-6 expression by these cells in a dose- and time-dependent m anner. Contamination with endotoxin was excluded by the use of polymyx in B and heat-inactivated cytokines. Further, we showed that IL-13, li ke IL-4, not only stimulated IL-6 production but also was able to indu ce overexpression of this cytokine in response to an inflammatory sign al such as lipopolysaccharide (LPS). In a previous study, we demonstra ted that IL-13, by inhibiting IL-6 and other cytokines produced by mon ocytes, exhibited an 'anti-inflammatory profile' comparable to that di splayed by IL-4. In contrast, we show here that IL-13, by stimulating IL-6 production by keratinocytes, may favour the installation of an in flammatory process at a local level and, here again, it acted like IL- 4. Therefore, according to the type of target cell, these two 'TH2 typ e' cytokines induce similar opposing effects on IL-6 production and ar e likely to be important cytokines in the regulation of inflammation a t both systemic and local levels.