Effects of 8-methoxypsoralen (8-MOP) and UVA on human lymphocytes.

Peripheral lymphocytes of 37 psoriatic patients are tested before and under PUVA treatment using as parameter the non specific stimulation effect of HgCl2 (10 microgram/ml) in culture, measuring the 3H-thymidine incorporation after the last 16 h of a 5-days culture. Oral 8-MOP in therapeutic doses is decreasing the lymphocyte stimulation as well as 8-MOP together with UVA irradiation during the first week of treatment. After 1 week, the stimulation is, on the contrary, significantly enhanced after irradiation. Lymphocytes isolated by centrifugation over Lymphoprep are submitted to PUVA conditions in petri dishes (Hank's solution 8-MOP 1 microgram/ml, irradiation with 350 nm, 93-372 mJ/cm2). The total cell number, the E-rosette formation (as marker for T-lymphocytes) and the EAC-rosette formation (as marker for B-lymphocytes) are determined. PUVA conditions have an energy dependent decreasing effect on the cell number, while the T- and B-cell proportions remain constant. UVA irradiation alone has such an effect only with high energies. 8-MOP without UVA has no significant influence on the cell number.