Psoriatic lesions were found to disappear spontaneously under haemodialysis [1 -4] or continuous peritoneal dialysis [5] without any additional topical application of tar and corticosteroids, and/or systemic treatment with cytostatic drugs.
Since both procedures recently introduced for therapy of psoriasis did not interfere directly with the excessive epidermal cell proliferation, a characteristic feature of the disease, the mechanism of the clearing of psoriatic lesions, remains completely unknown.
Some hypotheses were raised such as removal of an noxious substance probably of epidermal origin which may be filtered by the normal kidney, but not excreted owing to tubular reabsorption in psoriasis [5], as well as immunological activation, inactivation of substances, or alteration of feedback systems [4].
Taking into consideration that lymphocytes and polymorphonuclear leucocytes [PMNL] may play an important rote in the pathogenesis of psoriasis, we decided to explore an alternative hypothesis that not elimination of low molecular dialysable factor, but removal of white blood cells with dialysate could be reponsible for the clearing of psoriasis.
Lymphocytes and PMNL are known to form infiltrates in psoriatic lesions [6][7]. Furthermore, they could be a carrier of immunological factors, such as immune complexes, rheumatoid-like factors, anti-basal cell nuclei autoantibodies, or other immunoglobulins, and complement [8][9]. Complement activation products generated after binding of stratum corneum (SC) antigens with circulating anti-SC autoantibodies [t0] are presumed to exert chemotactic activity on PMNL which penetrate into the horny layer-forming Munro microabscesses [11]. Abnormalities of T-lymphocyte function were also reported [12].
The purpose of our paper was to determine : (1) whether white blood cells are removed by continuous peritoneal dialysis in a significant number, (2) whether some immunological factors related to these cells are eliminated on their surface