Two Methods por the Removal of Erythrocytes from Buffy Coats for the Production of Human Leukocyte Interferon

Two different methods of removing erythrocytes from buffy coats, with the ultimate aim of inducing the white blood cells for the production of leukocyte interferon, i.e., erythrocyte lysis with ammonium chloride, and erythrocyte agglomeration with hydroxyethyl starch, are compared. After two treatments with 0.83% NH4Cl all erythrocytes are lysed and most granulocytes are damaged, although the lymphocytes appear mostly unaffected (as judged by microphotography of Wright-stained smears). Treatment with 3% hydroxyethyl starch causes most erythrocytes to agglomerate and sediment to the bottom of a vessel in less than one hour; the leukocytes (lymphocytes as well as granulocytes), which remain in suspension, are morphologically intact. NH4Cl-treated leukocytes yield, on an average, 3.6 times less interferon than hydroxyethyl starch-treated leukocytes. Leukocyte viability, as judged by trypan blue exclusion does not appear much influenced by either NH4Cl or hydroxyethyl starch treatment. The advantage of hydroxyethyl starch apparently lies in the fact that its use leaves the granulocytes intact and thus obviates the undue release of proteolytic enzymes into the culture medium, with their concomitant deleterious effect on interferon production.