The role of interleukins 1, 6 and 8 as lymphocyte attractants in the photodermatoses polymorphic light eruption and chronic actinic dermatitis

The two photodermatoses, polymorphic light eruption (PLE) and chronic actin ic dermatitis (CAD), are characterized by lymphocyte-rich inflammatory infi ltrates, the pathogeneses of which are not fully understood. We have theref ore studied suction blister fluid (SBF) samples from patients with these co nditions before and at two time points after the induction of experimental lesions by means of a solar simulator; this SBF was then tested for the pre sence of selected cytokines known to induce peripheral blood lymphocyte (PB L) migration in vitro. A specific EL-4 NOB-1 bioassay was used to detect in terleukin (IL)-1 activity, which has already been noted in normal skin and this was found in pre-irradiation control samples as well as 1-3 h and 24 h post-irradiation in both patient groups, but at levels not significantly d ifferent from those of controls. Use of a B9 cell proliferation assay showe d no detectable IL-6-Iike activity pre-irradiation, but there was substanti al activity in samples at both post-irradiation time points in both patient groups. Further, in other experiments, retained SBF samples were tested in an in vitro PBL migration assay in the presence and absence of neutralizin g antibodies against IL-1 alpha, IL-1 beta, IL-6 and IL-8; considerable PBL attractant activity was noted in the preirradiation SBF from both patient groups: a finding consistent with previous reports of such activity in samp les from normal skin, and at least in CAD patients, a proportion of this ac tivity appeared to be due to IL-1, pre-incubation of SBF with neutralizing antibodies against IL-1 alpha and IL-1 beta reducing the effect significant ly. Substantial PBL attractant activity Mras present also in the SBF from 1 -3 h and 24 h post-irradiation samples in both patient groups and again, IL -l neutralizing antibodies reduced this in the 1-3 h and 24 h CAD samples. In addition, neutralizing antibodies against IL-6 and IL-8 reduced the acti vity in the 24 h PLE samples significantly and although not fully conclusiv e in the case of IL-1, these data suggest that IL-6, IL-8 and possibly IL-1 may be involved in the induction of PBL infiltrates, and perhaps other eve nts, in both PLE and CAD.