Enzymatic Heterogeneity of Granules in Human Leucocytes

Abstract

Homogenates of highly purified polymorphonuclear leucocytes and of a mixture of mononuclear leucocytes and platelets from human blood were separated by differential and isopyknic centrifugation. A heterogeneity in granules containing digesting enzymes was found in both cell preparations. Enzymes typical of lysosomes were found in the two cell preparations in a similar density range. Granules of low density were indicated in polymorphonuclear leucocytes by alkaline phosphatase. In both cell preparations a third granule, of lower density, seemed to exist enriched in amino acid naphthylamidase, acid hydrolases and in polymorphonuclear leucocytes also alkaline phosphatase and lysozyme. A remarkable difference between the two cell preparations was the occurrence of amino acid napthylamidase in denser granules of polymorphonuclear leucocytes only, although the nature of these granules could not be determined.