Studies on the interaction of human neutrophils with plaque spirochetes

Polymorphonuclear leukocytes (PMNs) encounter spirochetes in the diseased gingival crevice. The purpose of this investigation was to learn more about the nature and potential consequences of in vitro PMN‐spirochete interactions. Isolated spirochetes (various strains of Treponema denticola and T. vincentii) were incubated with human peripheral blood PMNs. PMNs were able to interact with these organisms demonstrating increased oxygen consumption, chemoluminescence, and phagocytosis. Serum was not an absolute prerequisite for phagocytosis, but oxygen consumption and chemoluminescence were generally not observed unless organisms were preopsonized with fresh serum. In spite of the fact that large numbers of spirochetes could be identified within PMN phagosomes, biochemical and ultrastructural evidence indicated limited degranulation on the part of the phagocytic cells. This can be contrasted to other plaque organisms which stimulated dose‐dependent degranulation in association with the phagocytic process. In fact, PMNs pretreated with soluble extracts of spirochetes, but not with non‐spirochetal organisms, were generally less responsive to zymosan‐induced degranulation. The data suggest that spirochetes may limit fusion of lysosomes to phagosomes and thereby influence the course of the inflammatory process in response to these as well as other organisms. These findings may be relevant in explaining the mechanisms of infection associated with the colonization of the gingival crevice by spirochetes.