An animal model and new photosensitizers for photopheresis.

Recently, photopheresis was introduced as a therapy for several T cell-mediated disorders. The treatment results in a specific immune response against the pathogenic clone of T cells involved. However, although promising there is controversy concerning the use of photopheresis in some diseases, e.g. systemic sclerosis. One of the problems is that there is not yet sufficient insight into the mechanism underlying the therapy. This lack of knowledge is partly caused by the fact that there are no easy-to-handle animal models available for photopheresis. This report describes such a model--a Wistar-derived rat with contact hypersensitivity (CHS); a T cell-mediated immune response. White blood cells from CHS rats were simultaneously exposed to 8-methoxypsoralen (8-MOP) and ultraviolet A radiation (UVA) and subsequently intravenously injected into other syngeneic rats suffering from the same disorder. This treatment appears to be very efficacious in suppressing the immunological response against the applied contact allergen, 2,4-dinitrofluorobenzene (DNFB). In addition, the generated suppression of CHS is highly specific and transferable. Furthermore, drugs other than 8-MOP (chlordiazepoxide, nitrofurantoin and chlorpromazine) also appear to be active in our model.