IN-SITU LOCALIZATION OF CHLOROQUINE AND IMMUNOHISTOLOGICAL STUDIES INUVB-IRRADIATED SKIN OF PHOTOSENSITIVE PATIENTS

Chloroquine can prevent photosensitivity reactions, but its mechanism of action is poorly understood, To investigate if the drug may interfe re with inflammatory or immunological mechanisms of the UV-induced ery thema of photosensitive patients, we studied the localization of chlor oquine in the skin and its effect on the epidermal/dermal expression o f IL-1, TNF-alpha, IL-6 and ICAM-1 and the occurrence of different lym phoid cells in normal skin and UVB-induced erythema in 8 patients with photosensitive discoid and systemic lupus erythematosus and 4 patient s with polymorphic light eruption (PMLE), before and during chloroquin e treatment, Using a specific monoclonal antibody against chloroquine, we found a strong granular staining pattern of mainly keratinocytes i n all biopsy specimens from normal and erythematous skin during chloro quine treatment, In non-irradiated skin, T lymphocytes, macrophages an d HLA-DR expressing cells were sparsely distributed within the dermis in similar amounts before and during chloroquine treatment, In UVB-ind uced erythema an increase in the number of these cells, mainly located in the dermal perivascular area, was seen before medication, During c hloroquine treatment such cellular infiltration was reduced, ICAM-1 ex pression was detected on the endothelium of dermal vessels but not on keratinocytes. The accumulation of chloroquine in the epidermis and th e decreased cellular infiltration in erythematous skin during chloroqu ine treatment indicate a local anti-inflammatory effect, This effect m ay be due to either unspecific UV-protective properties of the drug or to some specific downregulating action by chloroquine on keratinocyte function.