Changes in the surface properties of rabbit polymorphonuclear leucocytes, induced by bacteria and bacterial endotoxin

Rabbit peritoneal polymorphonuclear leucocytes were induced to aggregate by a variety of bacterial species. In the absence of serum, Gram-negative bacteria were more effective at inducing aggregation than Gram-positive. The most effective micro-organism tested, Acinetobacter sp. 199A, was readily phagocytosed and also induced extracellular secretion of the granule enzymes peroxidase and lysozyme. Isolated endotoxin from this bacterial species was highly effective in inducing aggregation and granule enzyme release. Endotoxin-induced aggregation was associated with a large increase in the amount of lactoperoxidase-catalysed iodination of surface protein. Only one iodinatable protein was detected, of molecular weight 150 000. It is postulated that phagocytosis of Gram-negative bacteria, followed by granule enzyme release, accelerates the rate of membrane recycling and that this brings new adhesive protein to the surface more rapidly.