Polymorphonuclear leukocyte phagocytosis of Capnocytophaga ochracea in three-dimensional plasma clots

We have studied the ability of human polymorphonuclear leukocytes (PMN) to phagocytose Capnocytophaga ochracea in three-dimensional fibrin meshworks. Phagocytosis was assessed in three systems: (1) the PMN and bacteria were mixed together with plasma and clotted; 60 +/- 13% phagocytosis occurred after 60 min; (2) PMN were overlaid on clots containing bacteria; the PMN migrated into the clot and after 60 min 52 +/- 7% phagocytosis was seen; (3) PMN had to migrate from within one clot into a second containing bacteria; phagocytosis after 60 min was 54 +/- 3%. In the clots, PMN released lysozyme but this was not significantly enhanced by phagocytosis. These findings indicate that PMN are capable of phagocytosing in each of the three-dimensional systems tested and that they are capable of both migration into and subsequent phagocytosis in a model that more closely mimics the in vivo structure in which PMN would normally perform.