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The lipid composition of leukocytes maintained in long-term culture was examined in order to clarify the role of immaturity in previously observed differences between normal mature leukocytes and leukemic cells. Cell cultures derived from three types of leukocytes were examined: normal lymphocytes, Burkitt lymphoma, and chronic myelocytic leukemia. Lipid extracts were analyzed for total lipid weight, phospholipids, neutral lipids, and glycolipids. Distribution of individual phospholipids was determined by quantitative two-dimensional thin-layer chromatography. The main phospholipids were phosphatidylcholine (51-54%) and phosphatidylethanolamine (24-25%), with smaller amounts of phosphatidylinositol, phosphatidylserine, sphingomyelin, and cardiolipin. All three types of cultured cells showed a remarkable similarity in total phospholipid content (17-18 x 10(-15) moles/cell) as well as in phospholipid distribution. More variation was seen in neutral lipid content. Glycolipid was abundant (17-23% of total lipid weight) and was present mostly as ceramide dihexoside. Compared with normal lymphocytes or polymorphonuclear leukocytes, the cultured cells showed increased phosphatidylcholine, decreased sphingomyelin, and decreased cholesterol content, similar to the changes found in leukemic leukocytes. These findings suggest that the altered lipid patterns found in leukemic leukocytes are a reflection of cell immaturity rather than a characteristic peculiar to the leukemic state.

Human leukemic cells with a marker (Philadelphia; Ph(1)) chromosome gave rise to granulocytic and mononuclear cell colonies when grown in vitro. All metaphases from a single colony were either Ph(1) positive or Ph(1) negative. No colonies contained a mixed cell population. This suggests that leukemic and normal cells exist simultaneously and that in vitro colonies are clonal in origin.