Phospholipid base exchange activity in the leukocyte membranes of patients with inflammatory disorders.

Phospholipid base exchange and cholinephosphotransferase (CPT) and ethanolaminephosphotransferase (EPT) activities were assessed in the membranes of neutrophils or lymphocytes from patients with various inflammatory disorders. Ethanolamine exchange activity was significantly enhanced in both neutrophils and lymphocytes from patients with active Behçet's disease, active systemic lupus erythematosus (SLE), and severe bacterial infections and slightly enhanced in those from patients with active rheumatoid arthritis (RA), compared with healthy controls. No abnormal findings were found in CPT, EPT, or serine or choline base exchange activities in the leukocytes from any of the diseased groups tested or in the ethanolamine exchange activity of patients with severe viral infections and inactive SLE, RA, and Behçet's disease. The authors have recently demonstrated the enhancement of transmethylation and phospholipase A2 activity in human leukocyte membranes at the height of inflammatory disease states, as well as the activation of leukocyte ethanolamine exchange by bioactive stimulants. These data postulate that phosphatidylethanolamine synthesis by the base exchange reaction may be the precursor of transmethylation and its subsequent activation of phospholipase A2, leading to the induction of arachidonic acid cascade.