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R J Boackle

Publications and source records attributed to R J Boackle.

15 recordsLinked to original sources
PubMed1991

Interaction of the envelope glycoprotein of human immunodeficiency virus with C1q and fibronectin under conditions present in human saliva.

Human saliva has been shown to reduce the infectivity of human immunodeficiency virus (HIV) particles in vitro. The factors in human saliva involved in this inhibition of HIV infectivity are unknown, although the salivary sediment of normal individuals has the major HIV neutralizing activity. Interestingly, the first complement component (C1) has been detected on the surface of the salivary sediment in the whole saliva of normal individuals. At the relatively low ionic strength of saliva, we determined that purified human C1q bound with high affinity to the envelope glycoprotein of HIV. Normally, the interaction of the C1q globular heads with immune complexes causes C1 activation. However, direct interactions between C1 and rgp120 (or rgp160) did not lead to C1 fixation, as determined by hemolytic studies with rate-limiting levels of C1, nor did rgp120 cause C1 activation as determined by activated C1s-mediated C4 conversion in normal human serum. Using ELISA, it was observed that intact C1, with the C1r2C1s2 tetramer associated with the collagen-like stem of C1q, did not bind to immobilized rgp120, whereas free C1q did bind. In addition, digestion of the C1q stem portion with collagenase completely eliminated its binding to rgp120. These findings suggest that the collagen-like stem region of C1q, rather than the globular heads, may participate in the binding to the envelope glycoprotein of HIV. Fibronectin, which is present in submandibular saliva, appeared to bind to rgp120 and to enhance the interaction of C1q with rgp120. It is conceivable that C1q and fibronectin, in binding and sequestering HIV particles (i.e. to the salivary sediment), may play an important role in the reduction of HIV transmission via saliva. Further studies will be needed to test the latter speculation.

Blotting, Western↗
PubMed1991

The interaction of salivary secretions with the human complement system--a model for the study of host defense systems on inflamed mucosal surfaces.

When complement first contacts salivary secretions, as when gingival crevicular fluid first meets saliva at the gingival margin, complement function is enhanced. The immediate potentiation of the complement system at equal volume ratios of serum to saliva is due to several factors, including the lower ionic strength of saliva when compared with serum and the presence of certain salivary glyproteins such as the nonimmunoglobulin agglutinins that appear to simultaneously activate C1 and affect (sequester) certain complement control proteins, such as Factor H. This initial potentiation of the complement cascade by saliva may aid in defending the area immediately above the gingival crevice from oral microbiota that are being coated with a combination of serous exudate components and salivary components. As serum becomes much more diluted with saliva (i.e., crevicular fluid moves away from the supragingival area), the acidic proline-rich salivary proteins (APRP) begin to disrupt the unbound C1q-C1r2-C1s2 macromolecular complexes. Thus, the APRP along with other C1 fixing substances in saliva appear to restrict complement function, but only when the ratios of saliva to serum exceed 250:1. Since certain salivary glycoproteins bind to viruses, the potentiation of the complement system by saliva may also play a role in neutralizing certain viral infections on mucosal surfaces where tissue transudates containing complement begin to contact mucosal secretions such as saliva. Again, the ratio of serous fluid to mucosal secretion appears to be an important factor. This article also discusses some of our preliminary data and speculations concerning the binding of the self-associating high-molecular-weight nonimmunoglobulin salivary agglutinins (NIA) with the envelope of the human immunodeficiency virus (HIV) and the possible cooperative role of C1q and fibronectin in aiding neutralization of HIV infectivity.

Complement Activation↗
PubMed1991

Characterization of C1 inhibitor binding to neutrophils.

In a previous study we have isolated neutrophil membrane proteins that non-covalently bind to native C1-INH (105,000 MW) and a non-functional, degraded C1-INH (88,000 MW; C1-INH-88). To further characterize the binding nature, we have designed a novel kinetic C1 titration assay which enables not only a quantification of the removal of fluid-phase C1-INH by neutrophils, but also a concomitant measure of residual C1-INH function. Native C1-INH, when adsorbed to EDTA-pretreated neutrophils, lost its function in the inhibition of fluid-phase C1. The non-functional C1-INH-88, which is probably devoid of a reactive centre, was found to block the binding of native C1-INH to neutrophils. Pretreatment of neutrophils with serine esterase inhibitors did not abrogate binding capacity of the cells for C1-INH, whereas the binding affinity for C1-INH was lost when the cells were pretreated with trypsin. An array of human peripheral blood leucocytes and several lymphoid cell lines has surface binding sites for C1-INH, but not on human erythrocytes and U937 cells. Binding was further confirmed using (i) C1-INH-microsphere beads to neutrophils, in which the binding was blocked when pretreating neutrophils with excess C1-INH or with trypsin, and (ii) radiolabelled C1-INH to neutrophils, which was competitively blocked by unlabelled non-functional C1-INH-88. Desialylation of C1-INH significantly reduced its binding affinity for neutrophils, indicating that the membrane receptor sites on neutrophils could be specific for the binding of sialic acid residues on C1-INH. Overall, our studies indicate that neutrophils or other leucocytes possess specific surface binding sites for the sialic acid-containing portion of C1-INH.

Binding, Competitive↗
PubMed1989

Interaction of dental cements with the complement system.

The relative complement-activating properties of several dental cements were investigated. After the cements were incubated with fresh human serum as a source of complement, the percent of the electrophoretic conversion was assessed by means of the C3 crossed-immunoelectrophoresis technique. It was determined that the ZnO-containing cements--which include zinc phosphate, zinc polycarboxylate, zinc oxide eugenol, and zinc hexyl vanillate--each caused C3 conversion, indicative of complement activation. Glass-ionomer cement, which does not contain ZnO, did not activate the complement system. In dose-response studies, ZnO at relatively low concentrations was effective in causing C3 conversion, while at higher concentrations ZnO appeared to block C3 conversion. Supernatants from ZnO suspensions also caused C3 conversion. Cement particle size, as well as soluble degradative products containing ZnO or Zn++, were suggested as possible factors contributing to the differential effects of the dental cements on complement activation and/or function.

Complement Activation↗
PubMed1988

Complement activation as a possible in vitro indication of the inflammatory potential of endodontic materials.

Samples of four brands of gutta-percha and the nine ingredients that make up one brand were studied in vitro to observe their interaction with the serum complement system, thus allowing for assessment of their possible inflammatory potential. Crossed immunoelectrophoresis of the third complement component was used as an indicator of complement activation. The four different brands of gutta-percha showed comparable complement activation as determined by C3 conversion. When the ingredients of one brand of gutta-percha were examined for complement-activating properties, major activities were associated with gutta-percha compound, agerite stalite-antioxidant, and titanium oxide food grade. The significance of the possible inflammatory potential of gutta-percha and its ingredients, as it relates to endodontic therapy, is discussed.

Complement Activation↗
PubMed1987

The effects of aggregated human IgG and IgG-immune complexes on the agglutination of bacteria mediated by non-immunoglobulin salivary agglutinins.

Non-immunoglobulin salivary agglutinins (SBA) for bacteria which bind to Streptococcus milleri TJ7 were isolated from parotid saliva and their interactions with human IgG studied. Purified SBA showed a single band on sodium dodecyl sulphate-polyacrylamide gel electrophoresis with a molecular weight of approx. 500,000. Heat aggregated human IgG (63 degrees C, 30 min), but not native IgG, interacted with SBA and thereby interfered with the ability of the SBA to agglutinate Strep. milleri. Immune complexes prepared from tetanus toxoid and isolated human IgG anti-tetanus toxoid antibody also inhibited salivary bacterial agglutination by SBA; antigen (tetanus toxoid) alone or antibody (anti-tetanus toxoid antibody) alone did not have this effect. Direct-binding studies with immobilized SBA on nitrocellulose paper showed that aggregated IgG bound to immobilized SBA and that this binding was inhibited by EDTA. Thus it appears that heat or specific antigen is able to induce an aggregation of IgG which results in the binding of the aggregated form of IgG to SBA.

Agglutination↗
PubMed1986

Evidence for the binding of human serum amyloid P component to Clq and Fab gamma.

In order to clarify the mechanism of interaction of serum amyloid P component (SAP) with complement, the interaction of SAP with C1q and with IgG was studied. It is known that SAP binds Sepharose in the presence of calcium. When purified 125I-C1q was incubated with SAP prior to Sepharose affinity chromatography, 125I-C1q was retained. However, in the absence of SAP, the 125I-C1q was not retained. To further examine the interaction of SAP with C1q, isolated SAP was incubated at varying ratios with C1q in the presence of 1.5 mM Ca2+. These mixtures were subsequently examined via crossed immunoelectrophoresis against goat anti-SAP. A change in the electrophoretic behavior of SAP was observed in the presence of C1q. In other studies, it was observed that SAP might interact with the collagen-like stem of C1q. In these latter studies, 125I-SAP was incubated with pepsin digests of C1q in a microtitre solid-phase binding assay. In addition, a microtitre solid-phase binding assay was utilized in order to investigate the possible binding of isolated 125I-SAP with IgG. Interestingly in the presence of Ca2+, human IgG and Fab gamma, but not Fc gamma, were found to bind 125I-SAP.

Antigen-Antibody Reactions↗
PubMed1978

Activation of the alternate complement pathway by peptidoglycan from streptococcal cell wall.

Activation of the alternate complement pathway in human serum by several bacterial components was compared. Peptidoglycan from group A streptococcal cell walls was the most active material, on a weight basis, followed by cell walls, protoplast membranes, and whole cells. The group-specific carbohydrate was inactive. Treatment of peptidoglycan with low concentrations of lysozyme or short periods of sonic treatment enhanced complement activation. High concentrations of lysozyme or extended sonic treatment of peptidoglycan destroyed or greatly reduced the capacity to activate complement. Lysozyme treatment of group A streptococcal cell walls or lipopolysaccharide had no measurable effect. Activation of the alternate complement pathway by group D streptococcal cell walls was destroyed by lysozyme. Activity of peptidoglycan was not inhibited by N-acetyl glucosamine, N-acetyl muramic acid, or D-alanine-D-alanine. Conversion of C3 and factored B by peptidoglycan was shown to occur by immunoelectrophoresis and crossed immunoelectrophoresis.

Animals↗
PubMed1978

The effects of human saliva on the hemolytic activity of complement.

Human saliva was tested for the presence of factors that affect the complement system. Parotid saliva and salivary fractions were incubated at 37 C with human serum as a source of complement. Samples removed from the mixtures within the first 15 minutes had higher levels of whole hemolytic complement activity than did appropriate controls. The final ionic strength of the saliva-serum mixtures was critical to the hemolytic activity of complement. After 60 minutes all serum-saliva mixtures had lower levels of hemolytic activity than did serum-buffer controls. With regard to whole saliva, the salivary sediment was found to be strongly complement-reactive.

Animals↗
PubMed1977

Detection of functional complement components in gingival crevicular fluid from humans with periodontal diseases.

Crevicular fluid was collected from patients with periodontitis by a capillary tube procedure. Complement component activities were determined by functional assay systems, with human complement, and partially purified human first complement component (C1) as controls. The complement-fixing properties of the dental plaque of each patient were also examined C1 activity in the crevicular fluid of all patients was approximately 1/8 of whole serum C1 and diminished rapidly with time after collection. There was no significant relationship between C1 concentration and crevicular fluid flow rate. Hemolytic activity of whole complement was also invariable detected when sufficient amounts (8 micronl) of crevicular fluid could be obtained. Dental plaque was found to fix C1. A role for crevicular complement in inflammatory periodontal disease is suggested.

Complement C1↗