HUMAN POLYMORPHONUCLEAR LEUKOCYTE RECEPTORS FOR STAPHYLOCOCCAL OPSONINS

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  • 1 January 1977
    • journal article
    • research article
    • Vol. 33  (2) , 231-239
Abstract
The presence of receptors on the plasma membrane of human polymorphonuclear (PMN) leukocytes for factors related to complement and for the Fc region of immunoglobulin [Ig] has not been clearly defined for opsonized bacteria. To separate the activity of these 2 receptors, the uptake of [3H]thymidine labeled staphylococci opsonized with normal serum or heat-inactivated serum was measured. Phagocytosis was depressed when bacteria opsonized with normal serum were incubated with trypsin-treated leukocytes, suggesting that complement receptors of human PMN leukocytes are trypsin-sensitive. Phagocytosis of bacteria opsonized with heat-inactivated serum was not depressed by trypsin, but was blocked by incubating PMN leukocytes with heat-aggregated IgG and by incubating opsonized bacteria with protein A. In experiments performed to quantify the number of bacteria attached to but not ingested by PMN leukocytes, it was shown that complement and Fc receptors participate in the ingestion phase of phagocytosis. Cell membranes of human PMN leukocytes possess 2 receptors for opsonized staphylococci; a complement receptor which is utilized when bacteria are opsonized in normal serum and an Fc receptor when bacteria are opsonized in heat-inactivated serum. Both receptors participate in the ingestion and the attachment phase of phagocytosis.