Selective stimulation of cutaneous interleukin 6 expression by skin allergens

Epidermal cells, both keratinocytes and Langerhans cells, are able to synthesize and secrete a variety of cytokines, many of which influence or are essential for the induction of skin sensitization and the elicitation of local inflammatory reactions. It has been proposed that it may prove possible to distinguish between contact allergens and skin irritants as a function of differential induction or upregulation of epidermal cytokine expression. In the present study we have addressed this by examination of the local cutaneous production of interleukin 6 (IL-6) following topical exposure of mice to oxazolone, a potent contact allergen, or to benzalkonium chloride (BZC), a skin irritant that is considered not to have a significant potential to cause skin sensitization. Both oxazolone and BZC could induce the production of IL-6 as measured by enzyme-linked immunosorbent assay in homogenates prepared from treated skin. However, when these chemicals were applied at concentrations that resulted in equivalent cutaneous inflammatory responses, based on induced oedema, only oxazolone provoked the production in skin of IL-6. Moreover, under these conditions exposure only to oxazolone resulted in the secretion by draining lymph node cells of measurable concentrations of this cytokine. These data suggest that the ability of oxazolone to stimulate local IL-6 production is not secondary simply to the induction of local inflammatory responses. As such, the results support the possibility that skin allergens and skin irritants may stimulate variable patterns of epidermal cytokine production.