Reduction in murine Langerhans cell ATPase staining following topical but not systemic treatment with steroid and non-steroid immunosuppressants

The effects on murine Langerhans cells (LC) of steroid and non-steroid immunosuppressive drugs which are commonly used for long-term immunotherapy of human patients were investigated. Hydrocortisone, prednisolone, cyclosporin A or azathioprine was administered daily for 7 consecutive days either topically by application to the skin, or systemically by intraperitoneal injection. LC densities were determined on the day following cessation of treatment by staining for the plasma membrane-bound enzyme adenosine triphosphatase (ATPase). All immunosuppressants caused a significant reduction in ATPase-positive LC when administered topically, but not systemically. The systemically administered drugs, although given in high concentration, may not have penetrated the epidermis in sufficient concentrations to disrupt the LC membrane. These observations are consistent with long term immunosuppressants depleting cutaneous LC by bone marrow suppression rather than by a direct effect on LC.