Methyltransferase and phospholipase A2 activity in membranes of neutrophils and lymphocytes from patients with bacterial and viral infections.

Phospholipid methylation and phospholipase A2 activation in the cell membrane are necessary for the induction of cell function in neutrophils and lymphocytes. We assessed the activity of membrane-associated methyltransferase and phospholipase A2 in neutrophils and lymphocytes from patients with acute and severe bacterial and viral infections. In bacterial patients, methyltransferase and phospholipase A2 activities of neutrophils were significantly enhanced, and [3H]methyl incorporation of lymphocytes was slightly increased. In viral infections, only phospholipase A2 activity of the lymphocytes was increased. These enhanced enzyme activities paralleled disease activity of the two disorders. The methylated products detected by two-dimensional thin-layer chromatogram were confined to methylated phospholipids, indicating that our assay system measures specifically the activity of methyltransferase which mediates the translocation of membrane phosphatidylethanolamine (PE) to phosphatidylcholine (PC) and lyso-PC(LPC). The two enzymatic activities of both neutrophils and lymphocytes in bacterial infections and phospholipase A2 of lymphocytes may, in part, have some correlation to the defense mechanism in these two disorders.