TYROSINE PHOSPHORYLATION IN PSORIATIC T-CELLS IS MODULATED BY DRUGS THAT INDUCE OR IMPROVE PSORIASIS

Background: The induction of protein tyrosine kinases (PTKs) is known to be a key element in the activation of lymphocytes. Objective: Becau se immunologic mechanisms are important in the pathogenesis of psorias is, we examined the time course of tyrosine-phosphorylated proteins (p -tyr) as a marker for cellular PTK activity in phytohemagglutinin (PHA )-stimulated T cells of psoriatic patients and healthy controls. Metho ds and Results: PHA-stimulated T cells from both groups expressed peak s of p-tyr after 15 min and 4 h. In T cells from psoriatics, the 15-mi n peak. was smaller but the 4-hour peak reached an enormous maximum, w hich was 270% higher than the basic p-tyr value. PHA-stimulated T cell s were additionally treated with psoriasis-provoking drugs (lithium, c hloroquine, propranolol and ethanol) and the two immunosuppressive dru gs cyclosporin A and FK 506. Lithium and propranolol were able to incr ease the p-tyr level after 15 min in PHA-stimulated T cells from psori atics in contrast to controls. Chloroquine and ethanol did not have a significant effect on T cells of both groups. CsA markedly diminished the phosphorylation of intracellular tyrosines in T cells of psoriatic s and controls, whereas FK 506 diminished the p-tyr level in controls only slightly. Conclusion: We have characterized important differences in p-tyr phosphorylation activities of psoriatic T cells compared to controls. This could be a hint to explain the known abnormalities of p soriatic T cells.