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Biomedical subjects

R N Powell

Publications and source records attributed to R N Powell.

At least 37 records · Page 2Linked to original sources
PubMed1987

In vitro modulation of T6 expression on gingival Langerhans cells by interleukin-1 inhibitors and ETAF.

T6 antigen is a highly specific marker for human Langerhans cells (LC). Previous studies have demonstrated that Interleukin-1 (IL-1) and an IL-1 inhibitor (ILS) modulate LC T6 expression (T6E) in explant culture. The present study examined the in vitro modulation of T6E by two molecules: epidermal-cell-derived thymocyte-activating factor (ETAF), and a bone-derived protein (BP) implicated in the control of bone homeostasis. The effect of purified ILS was also examined. ETAF mimicked the stimulatory effect of IL-1 on LC T6E, while BP depressed T6E in a manner resembling that seen with ILS. No agents altered Class II (DR and DQ) expression by LC. BP was a specific IL-1 inhibitor, and did not inhibit thymocyte proliferation in the standard IL-1 bioassay in the absence of IL-1. These results demonstrate that molecules resembling IL-1 or ILS can modulate T6E, and implicate locally produced ETAF and ILS in the regulation of T6E in the oral mucosa in vivo.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1987

Phenotypic and functional analysis of T cells extracted from chronically inflamed human periodontal tissues.

T-cell subsets extracted from chronically inflamed periodontal tissues were identified using monoclonal antibodies, and their functional activity was analysed using the autologous mixed lymphocyte reaction (AMLR). Tissue was obtained from a total of 33 adult periodontitis (AP) patients and 6 normal/marginal gingivitis (N/MG) patients. All AP patients had received repeated oral hygiene instruction and root planing prior to the surgery, and the majority (30 out of 33) had at least one site with greater than 6 mm loss of attachment from the cementoenamel junction within the surgical field. The N/MG patients had no loss of attachment, and probing depths were less than 3 mm. Single cell suspensions were obtained following collagenase digestion (90 minutes at 37 degrees C) and mechanical disruption of the tissue. T-cell subsets were identified using an indirect immunofluorescence assay on cells obtained from 19 AP patients and the 6 N/MG patients. The mean (+/- standard error) helper:suppressor (T4:T8) ratio for the AP patients was found to be 0.94 +/- 0.48 compared with 1.65 +/- 0.16 for the N/MG group and 1.51 +/- 0.12 for peripheral blood controls. HLA-DR positive macrophages were identified and were found to include both acid phosphatase (AcP) positive and adenosine triphosphatase (ATPase) positive populations. Functional analysis was carried out using cells extracted from the remaining 14 AP patients. Cells from six of these 14 patients were found to be capable of spontaneous proliferation. Co-culture experiments using autologous T and non-T populations revealed that cells from only four patients were able to respond in an AMLR while those from only one of the 14 patients were able to stimulate the AMLR.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Isolation and purification of ILS, an interleukin 1 inhibitor produced by human gingival epithelial cells.

Recent studies have described the presence of an interleukin 1 (IL-1) inhibitor (ILS) in supernatants from human gingival organ cultures. This report describes the isolation and purification of ILS. ILS was produced in serum-free medium and purified to apparent homogeneity by ion exchange chromatography and high pressure liquid chromatography. IL-1 and ILS eluted as discrete proteins using this system, with ILS appearing as a single protein band of 97,400 molecular weight on SDS-PAGE. ILS inhibited the effects of both murine IL-1 and IL-2 on thymocyte proliferation, and was heat resistant, moderately resistant to freeze-thawing and stable for 2 years at 0-4 degrees C or -20 degrees C. Production of ILS by gingival epithelial cell cultures was not affected by depletion of Langerhans cells, implying that ILS is primarily a keratinocyte product.

Chromatography, High Pressure Liquid↗
PubMed1986

The ultrastructure of human gingival Langerhans cells in health and disease.

There was a statistically significant shift towards increased proportions of type I Langerhans cells (containing many Langerhans-cell granules) and reduced proportions of both type II Langerhans cells (containing few granules) and indeterminate cells in diseased oral epithelium when compared to healthy oral epithelium. Langerhans cells and indeterminate cells were also seen in the sulcular epithelium of healthy and diseased specimens but never in junctional or pocket-lining epithelium.

Adult↗
PubMed1986

The autologous mixed lymphocyte reaction (AMLR) as a possible indicator of immunoregulation in chronic inflammatory periodontal disease.

Immunoregulatory control at both a local and systemic level is likely to be an important factor in the control of chronic inflammatory periodontal disease, explaining, at least in part, the individual variations between patients as well as the cyclical nature of the disease process. The autologous mixed lymphocyte reaction (AMLR), which is due to the stimulation of T cells by autologous HLA-DR positive non-T cells in the absence of specific antigen, is thought to be an in vitro correlate of immunoregulation. It is possible therefore, that the AMLR may detect systemic immunoregulatory phenomena in chronic inflammatory periodontal disease and that aberrations in the AMLR may be a manifestation of the disease and in turn reflect disease activity. Recent evidence does in fact suggest that the peripheral blood AMLR may identify particular disease groups, provided age and time of peak responsiveness are taken into account and hence may have an epidemiological application. It remains to be determined, however, that when used in a longitudinal fashion, the AMLR does reflect individual disease activity. These results are reviewed and areas of future research discussed.

Autoimmune Diseases↗
PubMed1986

The antimicrobial and clinical effects of a single subgingival irrigation of chlorhexidine in advanced periodontal lesions.

The antimicrobial effects of subgingival chlorhexidine (CH) irrigations on the pathogenic flora in advanced periodontal lesions were assessed. Changes in the patterns of colonization within the subgingival sites were monitored by differential dark-field microscopy, in 16 patients, over a period of 10 weeks. In addition, changes in the clinical parameters of the diseased sites were also monitored. Initial base-line evaluations were made for both the clinical and microbiological parameters. 4 sites of moderate to advanced periodontal disease were selected in each patient. These were randomly irrigated with a single dose of either 0.2% CH gel, 0.2% CH solution, or physiological saline, while 1 site was left as a control. The patients were seen weekly, until the 5th week, then at the 7th and 10th weeks. At each appointment, a microbiological sample was taken from the subgingival region of each site, together with an assessment of the clinical indices. Results indicated that a single irrigation of an 0.2% solution of CH or 0.2% CH gel had a marked effect in decreasing the % of spirochaetes and, to some extent, motile bacteria. There was a concomitant shift in colonization to cocci, fusiform and filamentous organisms in pockets that were irrigated; this coincided with a reduction in the % of bleeding sites. Various patterns of colonization were observed which have been described and may assist in differential dark field (DDF) monitoring of lesions. Bleeding on blunt probing was found to be correlated with a flora dominated by spirochaetes. No other correlations were found over the 10-week period between the other parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗
PubMed1986

Prevalence and distribution of gingivitis and dental caries in children aged 6-12 years in Brisbane primary schools.

A study of caries experience and gingivitis prevalence in 6-, 9- and 12-yr-old children attending primary schools in Brisbane was undertaken in November/December 1983. Children from high socioeconomic level (SEL) schools exhibited lower dmft and DMFT scores at all ages. At age 6 yr the proportion of children with caries-free primary dentitions was for high SEL Schools 70%, for middle SEL schools 52% and for low SEL Schools 23%. At 12 yr DMFT scores were 1.8 (high), 2.1 (middle) and 3.3 (low). Similar differences in gingivitis prevalence occurred, children from high SEL schools displaying a much lower proportion of bleeding sites than those from middle and low SEL schools. For selection of children at "high risk" to gingival disease for intensive prevention programmes, an increased emphasis on probing techniques is indicated to achieve diagnostic consistency.

Australia↗
PubMed1986

Chemiluminescence in the assessment of polymorphonuclear leukocyte function in chronic inflammatory periodontal disease.

Polymorphonuclear neutrophils (PMN's) constitute the primary host resistance factor against infection. They are prominent cells in both the gingival tissue and gingival sulcus in most forms of periodontal disease. Although defective PMN function has been implicated in the pathogenesis of localized juvenile periodontitis (LJP) and rapidly progressive periodontitis (RPP), this may not necessarily be the case in adult periodontitis (AP). A number of studies have failed to detect PMN dysfunction in AP. However, it may be that in this form of chronic inflammatory periodontal disease (CIPD) the defects in peripheral blood PMN function are subtle and the methods used may lack the necessary sensitivity. Chemiluminescence (CL) is the light energy produced by the PMN during its interaction with bacteria or other particles and has been demonstrated to correlate well with antibacterial integrity. Measurement of CL produced by phagocytically challenged PMN's may provide a very sensitive assay of the functional ability of these cells, and, hence, may be useful in assessing PMN activity in CIPD. Recent studies using PMN's obtained from periodontal diseased patients challenged with the periodontopathic organism Fusobacterium nucleatum have revealed an elevated CL response compared to non-diseased controls. These results are reviewed and areas for future research discussed.

Bacterial Physiological Phenomena↗
PubMed1986

Modulation of class II (DR and DQ) antigen expression on gingival Langerhans cells in vitro by gamma interferon and prostaglandin E2.

The effect of human and murine gamma interferon (IFN-gamma) on Class II (DR and DQ) expression by human gingival Langerhans cells (LC) was examined using an organ culture system. Human and murine IFN-gamma increased the expression of both DR and DQ antigens during a 72-h period. Maximal levels of DR expression (100% of T6+ cells) were produced within 6 h of IFN-gamma treatment and were maintained during culture. DQ expression was maximal (100% of T6+ cells) at 18 h and was more labile than DR. The effect of IFN-gamma on DR and DQ was abrogated by prostaglandin E2 (PGE) while indomethacin, and inhibitor of PGE synthesis, mimicked the effect of IFN-gamma on DR and DQ expression. Gingival keratinocytes maintained their expression of DR for 72 h in the presence of gamma-IFN, but did not express DQ under any of the culture conditions used in this study. These results demonstrate that gamma-IFN induces differential expression of Class II antigens in the oral mucosa in vitro, and suggest that gamma-IFN and PGE may be involved in the control of DR and DQ antigen expression in vivo.

Animals↗
PubMed1986

Interleukin-1 modulates T6 expression on a putative intra-epithelial Langerhans cell precursor population.

T6 is an antigen which is a highly specific marker for Langerhans cells. Previous studies have demonstrated that Interleukin-1 (IL-1) and an IL-1 inhibitor (ILS) modulate T6 expression (T6E) in explant culture. The present study examined the effects of IL-1 and ILS on T6E in dispersed gingival epithelial cell (EC) cultures. EC were obtained by trypsinization of gingival fragments obtained during periodontal surgery. T6E by EC was demonstrated using OKT6 monoclonal antibody in an immuno-peroxidase technique. In both unseparated and T6-depleted EC, IL-1 (0.5 U/mL) stimulated T6E, and this effect was abrogated by ILS (1:30). ILS alone depressed T6E in unseparated EC cultures. All effects were consistent between four- and 24-hour culture periods, and no treatment affected EC viability, thus excluding cell proliferation or necrosis as a vector for the action of IL-1 and ILS. These results indicate that a population of epithelial cells exists which is induced to express T6 under the influence of IL-1. IL-1 and ILS act in combination to regulate T6E on these precursor cells and on DR(-) Langerhans cells in gingival epithelium.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1986

In situ demonstration of natural killer (NK) cells in human gingival tissue.

Recent studies have raised the possibility that natural killer (NK) cell activity may play a role in tissue destruction in chronic inflammatory periodontal disease (CIPD). This study aimed to locate and identify these cells in healthy and diseased gingival tissue. Leu 4, Leu 7, and Leu 11 monoclonal antibodies were used to characterize lesions of CIPD and to identify NK cells. Gingival tissue from three patient groups was examined. Group 1 subjects participated in a 21-day experimental gingivitis study. Group 2 subjects were children aged less than 8 years who had gingivitis associated with deciduous teeth. Group 3 consisted of patients with CIPD undergoing periodontal surgery. In group 1, NK cells were absent in health (Day 0) and gradually increased in number with increasing inflammation up to Day 21. The number and distribution of NK cells in Group 2 subjects resembled those seen after a 21-day experimental gingivitis study. In Group 3 subjects, lesions of CIPD which contained greater than 90% Leu 4+ cells ("T cell" lesions) contained few Leu 7+ cells and no Leu 11+ cells. The greatest number of NK cells were found in the "B cell" lesions (less than 60% Leu 4+ cells). The absence of NK cells in gingival health and their presence in diseased gingiva suggests that these cells are involved in the immune response to the accumulation of plaque.

Adult↗
PubMed1986

Modulation of gingival Langerhans cell T6 antigen expression in vitro by interleukin 1 and an interleukin 1 inhibitor.

A human gingival organ culture system was used to test the hypothesis that interleukin 1 (IL-1) modulates the expression of the cortical thymocyte antigen T6 on Langerhans cells (LC). In cultures enriched with E. coli lipopolysaccharide, T6 expression peaked concurrently with supernatant IL-1 activity. Addition of exogenous IL-1 produced a dose dependent increase in LC T6 expression while not affecting the expression of the Class II antigens DR and DQ by LC. An IL-1 suppressor factor (ILS) was associated with the loss of T6 antigens which occurred in conventional organ cultures. ILS inhibited the thymocyte response to IL-1 and neutralized the effects of IL-1 on both thymocytes and LC. In isolation ILS depressed T6 expression by eliminating resting DR negative LC. This factor may act to regulative negatively, the action of IL-1 as has been suggested for IL-1 inhibitors of similar molecular weight.

Antigens, Differentiation, T-Lymphocyte↗