To determine whether topically applied biologically active drugs can be used to protect the human immune system from sunlight, we studied the effect of tamarind xyloglucan polysaccharide, a natural and common fruit constituent, on solar-simulated, ultraviolet radiation-induced local immunosuppression and erythema in humans. Immunosuppression was studied in humans using a nickel contact hypersensitivity recall model. Ultraviolet dose responses were generated to determine the extent to which tamarind affected the immune response in a group of 15 volunteers. The subsequent nickel-induced erythema was quantitated using a reflectance spectrometer. 0.1 μgml-1 of topical tamarind polysaccharide reduced ultraviolet radiation-induced immunosuppression. Frozen sections of biopsies taken were analysed by immunohistochemistry. Tamarind inhibited ultraviolet radiation-induced CD11c+ dendritic cell loss from the epidermis. The ultraviolet doses used in this study did not alter the number of Mac387+ macrophages or NP57+ neutrophils infiltrating the skin. Low dose xyloglucan polysaccharide from tamarind protected from immunosuppression in humans, possibly by reducing ultraviolet radiation-induced loss of dendritic cells, demonstrating that these types of drugs may be useful adjuncts to sunscreens for protection from skin cancer.
Keywords: tolerance, skin, dendritic cells, tumour immunity, ultraviolet, sunlight
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