PLATELET LACTATE-DEHYDROGENASE ACTIVITY IN SYSTEMIC LUPUS-ERYTHEMATOSUS - CORRELATION WITH ANTICARDIOLIPIN ANTIBODIES

Objective. To evaluate lactate dehydrogenase (LDH) activity in platele t subpopulations in systemic lupus erythematosus (SLE) and to correlat e platelet LDH activity with concentrations of anticardiolipin antibod y (aCL). Methods. Twelve female patients with SLE and 12 age matched f emale control subjects were studied, Platelets were separated on the P ercoll gradient, their density values controlled by density marker bea ds. LDH activity was measured after platelet lysis, expressed as nU/fl . ELISA were used to measure levels of IgG and IgM aCL. Results. A sig nificant increase of LDH activity with a significant correlation to Ig e and IgM aCL were found in small, light platelets with a volume < 5 m u(3) compared to large, dense platelets and to controls, LDH activity did not correlate with immunoglobulin classes, anti-DNA antibodies, an d complement fractions in small and large SLE platelets. Conclusion. O ur data suggest a possible chronic activation of subpopulations of sma ll platelets in patients with SLE independent of thrombotic process. L ow levels of aCL can mediate small platelet activation, Quantitative a nd qualitative analysis of the small, light platelets can serve a clin ical diagnostic purpose as an in vivo platelet activation index in SLE .