Effects of periodontopathic bacteria on IL‐1 and IL‐1 inhibitor production by human polymorphonuclear neutrophils

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Abstract
The effect of heat‐killed periodontopathic bacteria on the production of interleu‐kin‐1 (IL‐1) and an IL‐1 inhibitor by human polymorphonuclear neutrophils (PMN's) was examined. Peripheral blood was obtained from 18 healthy volunteers and the PMN's were separated using dextran sedimentation and Ficoll‐Paque density gradient centrifugation. The PMN's (5 ×105 cells/well) were cultured in serum‐free media with or without heat‐killed periodontopathic bacteria. Four gram‐negative periodontopathic bacteria were used; Bacteroides gingivalis FDC 381, Bacteroides forsythus FDC 338, Actinobacillus actinomycetemcomitans Y4 and Fusohacterium nucleatum FDC 263. The non‐oral Fusobaclerium mortifenint ATCC 25557 was used as a control organism. IL‐1 activity was assayed using thymocyte proliferation. The non‐oral organism F. mortiferum stimulated IL‐1 production by PMN's, in contrast none of the periodontopathic bacteria stimulated IL‐1 release although the bacteria themselves had an IL‐1 enhancing effect. Following fractionation of the periodontopathic bacteria stimulated PMN supernatants, an IL‐I inhibitory fraction was identified. These results may illustrate a further mechanism by which periodontopathic bacteria may evade the protective effect of PMN's and may also suggest a regulatory role for PMN's in chronic inflammatory periodonlal disease.