AGGREGATION OF HUMAN POLYMORPHONUCLEAR LEUKOCYTES DURING PHAGOCYTOSIS OF BACTERIA

Abstract

The process of aggregation of human polymorphonuclear leukocytes (PMN) during the uptake of bacteria was studied. Radiolabeled Staphylococcus aureus were opsonized in different sera, washed, resuspended in buffer and added to the PMN. Uptake of the bacteria and aggregation of the PMN were measured simultaneously. Maximal aggregation occurred within 6 min, when 5 .times. 106 PMN had phagocytosed 2.5 .times. 108 S. aureus. The effects of serum concentrations and different sera for opsonization of the bacteria on PMN aggregation were studied. Despite normal uptake, aggregation of PMN was low when bacteria were opsonized in complement-deficient sera. When PMN were treated with pronase to inactivate complement receptors on the cell surface of the PMN, and bacteria preopsonized in immune serum were added, no change in uptake occurred, although the degree of aggregation halved compared to control PMN. So, interaction between the bacteria and the complement receptors of the PMN cell membrane is needed for triggering the process of aggregation. By using dansylcadaverine and diphenylamine to modulate lysosomal enzyme release, azide or PMN from a chronic granulomatous disease patient to study the effect of the formation of O2 species, and theophylline, DB-cAMP or 8 Br-cAMP to increase cAMP levels, it was concluded that aggregation of PMN during phagocytosis was not dependent on O2 metabolism, degranulation or cAMP levels of PMN.