Periodontal diseases are inflammatory lesions of the gingival and periodontal tissue and are characterized by increased numbers of Gram negative organisms and an infiltrate of polymorphonuclear leukocytes (neutrophils) into the gingival crevice. Lipopolysaccharides (LPS) from enteric Gram negative microorganisms (e-LPS) have been demonstrated to be potent modulators of numerous immunological and pathological responses. While there are similarities among LPS molecules, there are also differences which are likewise reflected in differences in their biological activities. Recent evidence by others, using e-LPS, and in our laboratories, using LPS from periodontal pathogens (pp-LPS), suggests that certain neutrophil functions may also be modulated by LPS. It is noteworthy, however, that the e-LPS differs significantly from pp-LPS with respect to their effects on neutrophil function. Because neutrophils play a major role in the control of periodontal diseases, modulation of neutrophil function by the pp-LPS, may influence the course of these diseases. The purpose of this investigation is, therefore, to study the effect of LPS from Actinobacillus actinomycetemcomitans (associated with juvenile periodontitis) and Bacteroides gingivalis (associated with adult periodontitis), on neutrophil functions relevant to host defense. The effect of these LPS on neutrophil chemotaxis, phagocytosis' degranulation, and superoxide production will be compared to the effect of well characterized E. coli LPS. In addition, the possible modulation of neutrophil receptors for FMLP, C3b, IgGFc and C5a by these LPS will be studied. Finally, possible differences between the responses of neutrophils from normal and periodontal disease patients will be examined. In summary, the overall objective of this investigation is to gain a more detailed understanding of the role of LPS from periodontal pathogens in modulating neutrophil mediated host defense in periodontal disease.