Preparation and characterization of the plasma membrane of pig lymphocytes

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Abstract
Lymphocyte plasma membrane was isolated from minced pig mesenteric lymph node by differential centrifugation and by centrifuging through a sucrose density gradient. The yield of membrane was approx. 0.1% (dry wt. relative to wet wt. of lymph node). The purified material had a sucrose density of 1.14g/cm3 and consisted mainly of smooth vesicles. The membrane fraction contained, apart from protein and lipid, 59μg of carbohydrate, 11μg of sialic acid and 28μg of RNA/mg of protein; no DNA was detected. The cholesterol/phospholipid molar ratio was 1.01. Specific activities (μmol of product/h per mg of protein) of 5′-nucleotidase, succinate dehydrogenase, acid phosphatase and glucose 6-phosphatase were 10.1, 0, 0.51 and 0.30 respectively. The membrane vesicles were aggregated by an antiserum against pig lymphocytes and adsorbed the agglutinins to whole lymphocytes present in the antiserum; the membrane fraction was 28 times as effective as whole cells (on a dry wt. basis) in removing the lympho-agglutinins. Antisera against the membrane fraction agglutinated whole lymphocytes. It is concluded that the preparation represents the plasma membrane of small lymphocytes. The plasma membrane of pig thymocytes was isolated by using the same procedure. Its properties were similar to those of the lymphocyte plasma membrane.