Immunohistochemical analysis of contact sensitivity reactions in the guinea-pig using novel monoclonal antibodies: the influence of topical cyclosporin A.

When applied topically to guinea-pig skin from the time of epicutaneous antigen challenge, cyclosporin A (CsA) in ethanol:olive oil (1:2) significantly reduced contact sensitivity reactions to dinitrofluorobenzene (DNFB). This immunosuppressive effect was no longer apparent when initial drug administration was delayed for several hours, or when a non-immunosuppressive cyclosporin derivative was applied. Attenuation of skin reactions was accompanied by significant reductions in T cells recognized by putative pan T cell (CT7) and T cytotoxic/suppressor cell (CT6) monoclonal antibodies, whilst there were also concomitant decreases in basophil infiltration. There was no reduction in epidermal Langerhans cells or in infiltrating mononuclear cells recognized by MSGp9 (mainly dendritic cells) in CsA-treated reaction sites. There was no apparent reduction in Ia antigen expression (staining with MSGp8) on intralesional inflammatory cells with CsA treatment. Whilst demonstrating the efficacy of topical CsA in contact sensitivity, our findings suggest that more than one mechanism may be operative in the suppression of these cutaneous inflammatory reactions.