Interaction of gram‐negative periodontal pathogens with retinoic acid‐induced and dimethyl sulfoxide‐induced HL‐60 cells

Abstract

As a first step toward elucidating the reasons for differences among periodontal pathogens in their cytotoxic effects on HL-60 cells, we used transmission electron microscopy to examine morphological aspects of granulocyte-bacteria interactions. Unopsonized Actinobacillus actinomycetemcomitans strain Y4 and Bacteroides gingivalis ATCC 33277 adhered to, and were phagocytosed by, retinoic acid-induced and dimethyl sulfoxide-induced HL-60 cells. In contrast, there was only minimal interaction between Wolinella recta ATCC 33238 and these induced granulocyte-like cells. Only isolated examples of adherence of W. recta to HL-60 cells were seen. In specimens prepared for routine transmission electron microscopy, ingested W. recta were not observed. In immunogold experiments, phagocytosed W. recta were noted, but only rarely. Opsonization of A. actinomycetemcomitans, B. gingivalis and W. recta with specific antisera appeared to increase their level of interaction with the HL-60 cells. We suggest that the HL-60 cell line may be useful in elucidating structure-function relationships between human neutrophil-like cells and putative periodontopathogens.