An in vitro study of polymorphonuclear leucocyte-mediated injury to human gingival keratinocytes by periodontopathic bacterial extracts.

Human gingival keratinocytes were cultured and, after the first passage, subjected to cell detachment assays with polymorphonuclear leucocytes (PMNs) and/or sonic extracts from Actinobacillus actinomycetemcomitans Y4, and Eikenella corrodens 1073. The effector-to-target cell ratio was 30:1. Bacterial extracts alone caused no disruption of keratinocyte monolayers. PMNs alone also caused only minimal detachment after 14 h incubation. Adding A. actinomycetemcomitans to the PMN-keratinocyte co-cultures at the concentration of 100 micrograms/ml caused dramatic cell detachment. The effect of A. actinomycetemcomitans was heat labile and not inhibited by polymyxin B. Cell detachment was inhibited by alpha 1-antitrypsin, whereas catalase and superoxide dismutase could not prevent it. No lysis of keratinocytes was observed after incubation, as judged by 51Cr release. E. corrodens had little effect even at the concentration of 1000 micrograms/ml. H2O2 and partially purified PMN elastase also caused detachment of keratinocytes. These data indicate that PMNs can cause non-lytic detachment of keratinocytes when interacting with certain bacteria.