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A mutant of wild-type Streptococcus sobrinus 6715-13 has been isolated which resists aggregation by exogenous dextran. This variant is able to form adherent plaque deposits in vitro when cultured in the presence of sucrose and has dextranase activity. In these respects it is the complement of previously described isolates which are plaque formation defective but aggregation normal. Measurements of the incorporation of glucose from glucosyl-labeled sucrose into glucan by cell-associated glucosyltransferase enzyme activity and the thermal labilities of catalytic and receptor functions, as well as the binding of labeled dextrans to the cells, provide evidence that neither dextranase nor glucosyltransferase is the receptor involved in dextran-induced aggregation. Blockage of such bacterial aggregation by anti-glucosyltransferase or anti-dextranase sera suggests cross-reactivity between the antigenic determinants of proteins which recognize alpha(1-6) glucan linkages. A model is proposed, consistent with these and previous findings, in which enzymatic function precedes dextran receptor activity in emergence from the cell. It is also proposed that dextran receptor components of the multireactive glucosyltransferase enzyme(s) and dextranase(s) are spatially separate from, although functionally and antigenically related to, the receptors on the bacterial surface involved in dextran-induced aggregation.

Immune sera to strains of Streptococcus mutans were found to inhibit agglutination of bacterial suspensions to which either high-molecular-weight dextran or sucrose was added. This inhibitory activity was shown to be mediated by antibody of the immunoglobulin G class. A semiquantitative assay was developed which demonstrated cross-inhibition of dextran/sucrose-induced agglutination among several strains of S. mutans. Antiserum to a partially purified glucosyltransferase was found to lack agglutination inhibition activity, consistent with the hypothesis that the dextran-binding antigen detected by the assay is immunologically distinct from the glucan-synthetic enzyme. A model for glucan synthesis and binding consistent with the reported data is described.

Hybrid cell lines producing monoclonal antibodies against Bacteroides forsythus or Wolinella recta were generated by fusion of SP2/0 or FO myeloma cells with splenocytes from Balb/c mice immunized with formalinized cells of B. forsythus FDC 331 or W. recta D13a-g, respectively. Enzyme-linked immunosorbent assays and indirect immunofluorescence tests were used to analyze the distribution of the recognized antigens on a panel of 70 strains representing 35 taxa, most of which are members of the oral flora. All monoclonal antibodies--eight against B. forsythus and six against W. recta--proved specific for the immunizing species. Four of the monoclonal antibodies against W. recta recognized antigens expressed by only some of the tested W. recta strains, thus confirming the earlier noted antigenic heterogeneity of this species. Antibody binding patterns consistent with those previously described or distinct for new serogroups could not, however, be observed. Four of the eight anti-B. forsythus monoclonal antibodies bound to only two of the three tested B. forsythus strains. All the remaining monoclonal antibodies detected every strain tested of the respective species against which they were raised. Preliminary results indicated that several of these antibodies should be very useful for the direct identification and quantification of these organisms in subgingival plaque.

The purpose of our experiment was to evaluate the destructive potential of a strain of Actinomyces viscosus on the periodontium of sensitized rodents, describing the induced lesions on the basis of quantitative cytology. The experimental design comprised in principle the following procedures. Young germfree rats were immunized either by intravenous or intradermal injections with heat-killed cells of A. viscosus Ny 1 or sham immunized intradermally with physiological saline. After a period suitable for activation of the humoral and cell-mediated immune systems, Ny 1 was monoassociated in all animals by oral implantation. During the ensuing 42 days the animals were allowed to react against the continuous peripheral oral antigen challenge. Since A. viscosus is known as a heavy dental plaque-forming organism, the animals could be expected to develop local immunopathological lesions in the periodontal tissues. These lesions were then studied by quantitative cytology after sampling procedures allowing optimal tissue preservation. The degree of bone loss observed in all treatments was unrelated to the destructive capacity of the infiltrates, suggesting the presence of distinct mechanisms responsible for the activation of osteoclasts and factors interfering with fibroblast activity. Although the cellular composition of the infiltrated tissues was analyzed at the end of the experiment only, distinct stages of the lesions in the different treatments allowed reconstruction of the sequence of events. After an acute inflammatory phase, a classic delayed hypersensitivity reaction developed which was transformed after some time by a large superimposed plasma cell accumulation. The particular but undefined immune status was the significant factor determining the final type of peripheral infiltrative reaction.

In caries tests on rats, mutanase (mu-1,3-glucanglucano-hydrolase) was admixed in different quantities to a cariogenic diet. The animals were fed eight times a day with a feeding machine for 25 days. A highly significant inhibition of fissural caries was achieved by concentrations of over 50 MU per gram of diet. As a simultaneous plaque reduction was not observed, the effect of the enzyme appears to be due to reduced adhesion or colonization capacity of streptococcus mutans strains in the fissures.

The immunosuppressive effect of cyclosporin A (CS-A) was investigated in RIC-Sprague-Dawley rats. In vivo, CS-A totally abolished the formation of antibodies to the hapten dinitrophenyl (DNP) in rats immunized with DNP-keyhole limpet haemocyanin. In vitro, the effect of CS-A was investigated in spleen cell cultures stimulated by concanavalin A, phytohaemagglutinin or lipopolysaccharide. The suppression due to CS-A was more pronounced in cultures set up with cells from rats fed the drug than in spleen cell cultures from control animals supplemented with serum containing CS-A. Purified by filtration through Degalan-rat Ig-anti IgG columns, T lymphocytes from CS-A treated rats were no longer suppressed by CS-A serum in contrast to purified T cells obtained from control rats. Thus, CS-A seems to interfere with the mitogenic triggering of a subpopulation of T lymphocytes resulting in a functional clonal deletion.

The colonization on rat molars of S. sobrinus OMZ 176, S. mutans OMZ 376, or a combination S. sanguis OMZ 9 and S. sobrinus OMZ 176 after a short exposition to various fluoride solutions and disinfectants was tested in vitro. The test solutions included Act, Candida, Veadent, sodium fluoride, amine fluoride, stannous fluoride, zinc fluoride hexetidine, stannous fluoride/amine fluoride solutions, chlorhexidine and water. The sterilized rat molars were immersed in the above test solutions for 60 seconds, then incubated with streptococci in broth for 8 hours, again dipped into the same test solutions for 60 seconds and reincubated for an additional 30 hours. The streptococcal suspension contained 14C labelled sucrose solutions. The deposits on the molars were dissolved in 6N potassium hydroxide during 16 hours. Finally, the beta rays emitted by the dissolved radiolabelled suspension were counted using a scintillation counter. The sodium fluoride containing solutions exerted no or a very limited effect on the bacterial deposits. In contrast to the other test solutions, sanguinaria extract (Veadent mouth rinse) mildly inhibited the S. sobrinus and S. mutans deposits, but plaque formation by the combination of streptococci was not hampered. Zinc fluoride/hexetidine, amine fluoride and stannous fluoride/amine fluoride solutions had a distinct and significant inhibitory effect on S. sobrinus and S. mutans deposits, but only a weak effect when mixed cultures were used for plaque formation. Chlorhexidine significantly inhibited the deposits of the three bacterial strains used in these experiments.

The histopathology of human root caries was examined in extracted teeth by different optical methods. The present part of the study details the sequential stages of initial caries in both cementum and peripheral dentin. Significant differences are shown between the mechanisms operating on the various dental hard tissues during development of caries. Histologically distinguishable reaction patterns depended on both the degree of the cariogenic challenge and the respective structural features of cementum and peripheral dentin. Earliest lesions, histologically visible as small clefts traversing cementum and extending into peripheral dentin, were clinically not detectable. Cementum was stepwise destroyed until peripheral dentin became exposed. The exposed peripheral dentin was sclerosed and tubule-free. Demineralization of dentin preceded the degradation of the organic matrix. Frequently, a hypermineralized layer occurred in both cementum and exposed dentin. Its localization was not identical with the anatomical surface. Initial penetration of bacteria into peripheral dentin occurred along small clefts. Breakdown of the organic matrix was the final step in the destructive phase of the carious process.