title: Phospholipid composition of human monocytes and alterations occurring due to culture and stimulation by C3b.
abstract: The phospholipid composition of human peripheral blood monocytes has not been previously reported, due to difficulty in isolating these cells in a purified state. In this study, monocytes were purified by counterflow centrifugation without selective adherence, and were characterized with the use of fluorescent monoclonal antibodies to T and B lymphocytes and monocytes by flow cytometry. These platelet-free cell preparations contained less than 5% T cells and less than 3% B cells. Isolated monocytes, which were rapidly frozen after isolation, contained phospholipids (in order of decreasing concentrations) as follows: phosphatidylcholine greater than phosphatidylethanolamine greater than sphingomyelin greater than phosphatidylserine greater than phosphatidylinositol greater than cardiolipin. A small amount of lyso-PC, but no lyso-PE, phosphatidic acid or lyso-PI, was found. The effect of culturing these cells in the presence or absence of a known stimulant of monocyte prostaglandin E and thromboxane release, the C3b fragment of the third component of human complement (C3), was studied with regard to phospholipid composition. Monocytes cultured without stimulant for 24 h contained 3-4% more sphingomyelin than did uncultured cells, and lyso-PC concentrations were consistently elevated. The addition of the stimulant C3b to cultured cells resulted in enhancement of release of immunoreactive prostaglandin E into culture supernatants, without affecting the release of lysosomal enzymes. Analysis of the phospholipid content of cells cultured in the presence of C3b revealed that there was a significant decrease in total PI compared to cells cultured in the absence of C3b, in addition to an increased concentration of sphingomyelin and lyso-PC when compared to freshly isolated cells. These changes occurred in the absence of elevated concentrations of phosphatidic acid.
mesh_terms: D000118:Acetylglucosaminidase / Q000378:metabolism; D000911:Antibodies, Monoclonal; D002469:Cell Separation; D002478:Cells, Cultured; D003179:Complement C3b / Q000502:physiology*; D005966:Glucuronidase / Q000378:metabolism; D006801:Humans; D009000:Monocytes / Q000378:metabolism*; D009113:Muramidase / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D010743:Phospholipids / Q000097:blood*; D011453:Prostaglandins / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D010713:Phosphatidylcholines; D010716:Phosphatidylinositols; D010743:Phospholipids; D011453:Prostaglandins; D003179:Complement C3b; D009113:Muramidase; D005966:Glucuronidase; D000118:Acetylglucosaminidase