Multiple Choice Questions Test - IV (Basic Periodontology).
When naïve B-cells encounter invading pathogens, in particular extracellular micro-organisms, they undergo affinity maturation via clonal selection, somatic hypermutation, and Ig receptor editing. When activated, B-cells bearing the higher or highest affinity for Ag are rescued from apoptosis. Subsequently, these B-cells with mutated B-cell receptor genes, located in the germinal centers of regional lymph nodes, undergo further isotype- switching and differentiate into effector or memory B-cells. Certain cytokines such as interferon-γ (IFN-γ), interleukin-4 (IL-4), IL-5, IL-10, IL-12, transforming growth factor-β (TGF- β), anti-CD40-Ligand/CD40, and bacterial lipopolysaccharides (LPS) are potent stimulators of antibody class-switching.
Reference: Yen-Tung A. Teng. The Role of acquired immunity and Periodontal Disease Progression. Crit Rev Oral Biol Med 14(4):237-252 (2003)
FcγRIIa receptoris found on all granulocytes, antigen-presenting cells, platelets, endothelial cells and a subset of T cells. FcγRIIIa is present on monocytes and macrophages, NK cells and a subset of T cells. The FcγRIIIb is the major IgG receptor of neutrophils.
Reference: Loos, B. G., Leppers-Van de Straat, F. G., Van de Winkel, J. G. & Van der Velden, U. (2003) Fc gamma receptor polymorphisms in relation to periodontitis. Journal of Clinical Periodontology 30, 595–602.
Interleukin-1β (IL-1β) and several other cytokines, including IL-1α, tumor necrosis factor (TNF), and lymphotoxin, stimulate bone resorption and also inhibit bone formation in vitro, but IL-1β has most potent effects in mediating bone resorption.
Reference: Alexander MB, Damoulis PD (1994). The role of cytokines in the pathogenesis of periodontal disease. Curr Opin Periodontol 1:39-53.
ACC are small, short (0.4×1 µm) straight or curved rods with rounded ends. Electron microscope studies have demonstrated membrane vesicles that appear to release from cells. On blood agar, colonies are small, gray to white, translucent, smooth and non-haemolytic. Growth is stimulated by addition of CO2 and species grows well in 5-10 % of CO2. ACC ferments a range of sugars including glucose and fructose but not sucrose and lactose. Acid end products include lactate, succinate, acetate and propionate.
References: Zambon JJ. Actinobacillus actinomycetemcomitans in human periodontal disease. J Clin Periodontol 1985: 12: 1-20
Slots J. Selective medium for isolation of Actinobacillus actinornyceterncornitans. J Clin Microbiol 1982: 15: 606- 609
Like all other epithelial tissues, junctional epithelia undergo turnover, which means replacement by cell division in the basal layer and migration of the daughter cells to the surface of the epithelium where they eventually die and are shed into the oral cavity. After shedding these epithelial cells come into oral fluid (mainly saliva) in the mouth and are then called salivary corpuscles. Junctional epithelium has a very high turnover rate, estimated to be about 6 days in humans. The turnover rate of JE is important because it should be taken into account when evaluating healing in patients following surgical procedures involving the periodontal tissues.
Reference: Herbert F. Wolf, Klaus H. Rateitschak Color Atlas of Dental Medicine: Periodontology: Periodontology
In Ehler-Danlos syndrome, periodontal disease can be associated to syndromes type I, VII, III, or IV. Only in relation to type I is a predisposition to periodontal disease described, while type VIII presents as early onset periodontitis, premature loss of permanent teeth, fragility of the alveolar mucosa and gingival bleeding.
Reference: Zacy Carola Nualart Grollmus, Mariana Carolina Morales Chávez, Francisco Javier Silvestre Donat. Periodontal disease associated to systemic genetic disorders. Med Oral Patol Oral Cir Bucal 2007;12:E211-5.
Most clinically relevant bacteria are aerobic, facultatively anaerobic, or strictly anaerobic. Aerobic bacteria use oxygen as a terminal electron acceptor and grow well in room air. Anaerobic bacteria are unable to use oxygen as an electron acceptor, but some aerotolerant strains will still grow slowly and poorly in the presence of oxygen. Oxygen is inhibitory or lethal for strictly anaerobic bacteria. In addition to oxygen, the availability of CO2 is important for growth of certain bacteria. Organisms that grow best with higher CO2 concentrations (i.e., 5% to 10% CO2) than is provided in room air are referred to as being capnophilic. For some bacteria a 5% to 10% CO2 concentration is essential for successful cultivation from patient specimens.
Gingipains are cysteine proteinases produced by P. Gingivalis which are responsible for about 85% of the general proteolytic activity generated by this bacterium. These enzymes are encoded by three genes (rgpA, rgpB, and kgp). In most P. gingivalis strains the gingipains are associated with the bacterial cell surface. Whereas RgpA and Kgp occur in a form of noncovalent complexes of unique catalytic domains with practically identical hemagglutinin/adhesion domains, RgpB is a single-chain enzyme.
Reference: Katarzyna Popadiak, Jan Potempa, Kristian Riesbeck and Anna M. Blom. Biphasic Effect of Gingipains from Porphyromonas gingivalis on the Human Complement System. J Immunol 2007; 178:7242-7250.
Studies have implicated Porphyromonas gingivalis, Fusobacterium nucleatum and Tannerella forsythia in connective tissue attachment loss and periodontal inflammation and these organisms have been isolated from atherosclerotic plaque.
Reference: Ford PJ, Gemmell E, Hamlet SM et al. Cross-reactivity of GroEL antibodies with human heat shock protein 60 and quantification of pathogens in atherosclerosis. Oral Microbiol Immunol 2005; 20: 296–302.
Humoral immune system is also affected by smoking. Macrophages are components of both cellular and humoral immunity. It has been demonstrated that alveolar macrophages from smokers exhibit reduced expression of class II MHC.
Pankow W Neumann K, Ruscheff J, Schroder R, von Wichert P (1991). Reduction in HLA-DR density on alveolar macrophages of smokers. Lung 169:255-262.
Mancini NM, Bene MC, Gerard H, Chabot F, Faure G, Polu IM, et al. (1993). Early effects of short-time cigarette smoking on the human lung: a study of bronchoalveolar fluids. Lung 171:277-291.