AN INVITRO STUDY OF POLYMORPHONUCLEAR LEUKOCYTE-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 mug/ml caused dramatic cell detachment. The effect of A. actinomycelemcomitans was heat labile and not inhibited by polymyxin B. Cell detachment was inhibited by alpha1-antitrypsin, whereas catalase and superoxide dismutase could not prevent it. No lysis of keratinocytes was observed after incubation, as judged by Cr-51 release. E. corrodens had little effect even at the concentration of 1000 mug/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.