William P. McArthur

Leukotoxic activity in different strains of the bacterium Actinobacillus actinomycetemcomitans isolated from juvenile periodontitis in man

Abstract Type culture strains and dental isolates (from juvenile periodontitis) of Act. actinomycetemcomitans (Aa) were tested for their ability to kill human polymorphonuclear leukocytes (PMN) in vitro. The majority of Aa, as well as sonic extracts prepared from these organisms, rapidly destroyed PMNs, shown by the extracellular release of lactate dehydrogenase from PMNs and by degenerative ultrastructural alterations. The leukotoxic properties of Aa could be modulated by serum: normal human sera enhanced killing but juvenile periodontitis or various rabbit anti-Aa sera neutralized toxic activity. Whereas toxic and non-toxic strains of Aa shared common antigens, immunologic analyses revealed a unique antigen in sonic extracts of leukotoxic organisms. Thus Aa-derived leukotoxin may be an aetiologic vector in juvenile periodontitis.

Lactoferrin-mediated modulation of mononuclear cell activities: I. Suppression of the murine in vitro primary antibody response

Abstract The effect of the iron-binding glycoprotein lactoferrin (LF) on the in vitro primary antibody response of mouse splenic cells to a T-lymphocyte-dependent antigen, sheep erythrocytes (SE), and a T-lymphocyte-independent antigen, trinitrophenolated Brucella abortus , was examined. Both iron-saturated and native LF (8% saturated) at 10 −10 to 10 −6 M concentrations but not transferrin (an iron-binding glycoprotein similar to LF) significantly ( P

Interaction of inflammatory cells and oral bacteria: Release of lysosomal hydrolases from rabbit polymorphonuclear leukocytes exposed to Gram-positive plaque bacteria

Abstract The purpose was to ascertain whether Gram-positive bacteria derived from dental plaque could stimulate the release of lysosomal enzymes from rabbit peritoneal exudate polymorphonuclear leukocytes (PMNs). Microorganisms which were capable of inducing periodontal syndromes in experimental animals and of synthesizing extracellular polysaccharides were capable of triggering hydrolase release from PMNs. On the other hand, bacteria which did not produce extracellular polysaccharides under the conditions employed were relatively inactive in inducing a PMN-release response. Lysosome release resulting from bacterial-PMN interactions may be one important mechanism in the pathogenesis of gingivitis and periodontal disease.

Redirecting the Humoral Immune Response against Streptococcus mutans Antigen P1 with Monoclonal Antibodies

ABSTRACT The adhesin P1 of Streptococcus mutans has been studied as an anticaries vaccine antigen. An anti-P1 monoclonal antibody (MAb) bound to S. mutans prior to mucosal immunization of mice was shown previously to alter the amount, specificity, isotype, and biological activity of anti-P1 antibodies. The present study was undertaken to screen this and four additional anti-P1 MAbs for immunomodulatory activity when complexed with S. mutans and administered by a systemic route and to evaluate sera from immunized mice for the ability to inhibit adherence of S. mutans to immobilized human salivary agglutinin. All five MAbs tested influenced murine anti-P1 serum antibody responses in terms of subclass distribution and/or specificity. The effects varied depending on which MAb was used and its coating concentration. Two MAbs promoted a more effective, and two others a less effective, adherence inhibition response. An inverse relationship was observed between the ability of the MAbs themselves to inhibit adherence and the ability of antibodies elicited following immunization with immune complexes to inhibit adherence. Statistically significant correlations were demonstrated between the levels of anti-P1 serum immunoglobulin G2a (IgG2a) and IgG2b, but not of IgG1 or IgG3, and the ability of sera from immunized animals to inhibit bacterial adherence. These results indicate that multiple anti-P1 MAbs can mediate changes in the immune response and that certain alterations are potentially more biologically relevant than others. Immunomodulation by anti-P1 MAbs represents a useful strategy to improve the beneficial immune response against S. mutans.

Activation of the complement system by some Gram-positive oral bacteria

Abstract Actinomyces viscosus 19246, T 14 V and T 14 AV, Streptococcus mutans and Streptococcus sanguis consumed complement in vitro . Complement (C) profile analysis revealed that C 4 and C 3–9 were consumed concomitantly in unadsorbed human serum. In serum from which naturally occurring agglutinating antibodies had been removed, the same microorganisms caused C 3–9 consumption in the absence of a demonstrable loss of C 4 activity. Congenitally C 4 -deficient guinea-pig serum (C 4 D) supported a similar consumption of C 3–9 . The Gram-positive plaque microorganisms tested activated serum complement by the classical as well as the alternate pathways. Dental plaque microorganisms may cause a similar activation of gingival crevicular fluid complement in vivo , thus resulting in complement-mediated inflammatory processes.

Immune modulation of connective tissue functions: Studies on the production of collagen synthesis inhibitory factor by populations of human peripheral blood mononuclear cells

Abstract It has been shown previously that a soluble factor(s) from human peripheral blood mononuclear cells was capable of specifically suppressing collagen synthesis by normal human dermal fibroblasts (S. A. Jimenez, W. McArthur and J. Rosenbloom, J. Exp. Med. 150 , 1421, 1979). In this communication, the cell sources and the conditions for synthesis of this collagen synthesis inhibitory factor (CSIF) are identified. CSIF production by mononuclear cells was directly related to the number of cells in culture and was significantly enhanced by a variety of mitogens and by antigens. Homologous serum or bovine serum albumin was required for CSIF production and maximal levels were reached 48 hr after stimulation. Thymus-derived lymphocytes appeared to be the main cells responsible for CSIF synthesis but B lymphocytes also produced the factor in response to proper B-cell mitogens. Preparations of plastic-adherent mononuclear cells were also found to produce increased CSIF but it was not possible to exclude completely the presence of T lymphocytes in these preparations and therefore, the cell source of CSIF in these preparations was not clearly established. Through the use of metabolic inhibitors it was shown that CSIF production required de novo protein synthesis but not cell division. Indo-methacin had no effect on either the production of CSIF or on CSIF-mediated inhibition of collagen synthesis. The results indicate that CSIF has the classic characteristics of a lymphokine and suggest a mechanism by which the immune response could modulate connective tissue function.

Activation of the alternative pathway of complement in human serum byPropionibacterium acnes (Corynebacterium parvum) cell fractions

Activation of the alternative pathway of complement is known to be initiated by bacterial structures. We have fractionatedPropionibacterium acnes cells, purified various cell fractions, and tested their complement-activating ability in human serum chelated with ethyleneglycol bis- (β-aminoethylether)-N, N1-tetraacetic acid. The majority of complement-activating activity was localized in the wall fraction. This activity was resistant to lipid extraction, protease, RNAse, DNAse and lysozyme treatment. NaIO4, formamide, and hot (but not cold) trichloraacetic acid (TCA) extraction ablated the complement-activating capacity of cell walls. Compounds removed by extraction failed to consume significant hemolytic activity against antibody-coated sheep erythrocytes (EA). Addition of TCA-extracted soluble material to cell wall suspensions resulted in an inhibition of hemolytic consumption by the cell wall. These results indicate that, inP. acnes, complement-activating molecules are located in the cell wall and are carbohydrate in nature. Peptidoglycan, lipid, protein, and nucleic acids do not appear to contribute to the cell walls ability to activate complement.

Electron microscopic study of the interaction of oral microorganisms with polymorphonuclear leukocytes.

Abstract A variety of Gram-positive plaque bacteria can trigger lysosomal enzyme release from rabbit polymorphonuclear leukocytes (PMNs) in vitro . This electron microscopic study was undertaken to assess the correlation between phagocytic activity by PMNs and lysosome release to Streptococcus mutons 6715, Streptococcus sanguis G9B, and Actinomyces viscosus T14. PMN phagocytic activity was quantitated by determining the percentage of cells showing evidence of phagocytosis (phagocytic index) and the number of bacteria within the PMNs (avidity index). High phagocytic activity was accompanied by vigorous PMN lysosomal enzyme release. On the other hand, when PMNs exhibited low phagocytic activity lysosomal enzyme release was minimal. For example, Streptococcus mutans grown in brain-heart infusion broth did not induce significant lysosome release or demonstrable phagocytic activity by PMNs. In contrast, Strep. mutans grown in BHI containing sucrose or pre-incubated with anti- Strep. mutans antibodies acted as potent triggers of lysosome release and PMN phagocytosis. Our results indicate that various species of oral Gram-positive bacteria trigger different responses from PMNs and that phagocytic activity of PMNs correlates well with the ability of these microorganisms to stimulate lysosomal enzyme release.

Characterization of a lymphokine produced by human T cells which inhibits collagen synthesis

Human lymphocytes, isolated from peripheral blood, were cultured for 48 hr in a defined medium containing 10 mg/ml bovine serum albumin and phytohemagglutinin. A lymphokine which inhibits collagen synthesis by cultured human dermal fibroblasts was purified from the lymphocyte incubation medium by successive steps of ammonium sulfate precipitation, gel filtration chromatography, and isoelectric focusing. Good recovery of this collagen synthesis inhibitory factor (CSIF) was obtained and a factor with an approximate molecular weight of 55,000 and a pI of 6.2 was isolated. The purification of the factor should permit further studies on its mechanism of action.

Inhibition of chemiluminescence in human neutrophils by dapsone.

Dapsone at doses of 0·5 to 5·0 μ/ml was found to produce a dose‐dependent inhibition of opsonized zymosan‐induced human polymorphonuclear leukocyte(PMN) chemiluminescence (CL) in vitro. Simultaneous exposure of PMN to dapsone and zymosan was as effective in reducing CL as preincubation of PMN with dapsone. Preincubation of PMN with dapsone followed by washing, resulted in the loss of dapsone‐mediated CL inhibition, indicating that dapsone did not permanently alter the CL‐generating mechanism and that the drug had to be present to inhibit CL. Dapsone did not absorb light at the wavelength of CL and was not toxic to PMN at concentrations tested. Sodium azide, an inhibitor of myeloperoxidase‐mediated CL inhibited PMN CL to the same degree as dapsone. When incubated together with PMN, dapsone and azide did not produce an additive inhibition of CL. These data suggest that inhibition of myeloperoxidase may be the mechanism by which dapsone inhibits PMN CL.