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Isolation and Characterization of Plasma Membranes from Human Leukemic Lymphocytes¹

Service de Médecine Interne et d'Investigation Clinique, Institut Jules Bordet, Bruxelles, Belgium

A method for the isolation of lymphocyte plasma membranes from patients with chronic lymphocytic leukemia is described. Lymphocytes were disrupted in a hypotonic bicarbonate medium using a Dounce homogenizer. The plasma membranes fraction was finally collected from a continuous sucrose gradient at density 1.115 (g/ml). Electron micrographs of this material showed membranes and small dense vesicles of unidentified origin. The enrichment of this fraction in adenosine 5'-monophosphatase, Mg²⁺:Na⁺:K⁺:adenosine triphosphatase, and uridine diphosphatase, considered as plasma membrane markers, was, respectively, 43-, 23-, and 42-fold. The only noticeable contamination of plasma membranes was lysosomal material as attested by a 4.7-fold increase in ß-glucuronidase specific activity. It was calculated, however, that lysosomes accounted for less than 10% in the plasma membrane fraction.

The concentration of cholesterol and total phospholipids per mg of plasma membrane protein was, respectively, 185 and 965 µg, thus 10- and 6-fold higher than in the whole homogenate. The molar ratio of cholesterol to phospholipids was 0.38.

¹ This work was supported by a grant from the Fonds Cancérologique de la Caisse Générale d'Epargne et de Retraite de Belgique.

² To whom requests for reprints should be addressed at Department of Medicine, Institut Jules Bordet, 1, rue Héger-Bordet, 1000 Bruxelles, Belgium.

Received 4/16/73. Accepted 7/23/73.