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R L Boyd

Publications and source records attributed to R L Boyd.

At least 73 records · Page 4Linked to original sources
PubMed1993

Isolation of a cDNA encoding thymic shared antigen-1. A new member of the Ly6 family with a possible role in T cell development.

We have previously characterized a novel mouse thymocyte marker, defined as thymic shared Ag-1 (TSA-1), present on both immature thymocytes and a subset of thymic medullary epithelial cells. MTS 35, a mAb specific for TSA-1, alters T cell differentiation when added to fetal thymic organ cultures, suggesting TSA-1 may be important for T cell development in the thymus. In this study, we describe the isolation of a cDNA encoding TSA-1 using transient expression of COS-7 cells and selection with MTS 35. The predicted amino acid sequence of this cDNA encodes a 15 to 17-kDa protein and the expressed protein is linked to the membrane via a phosphatidylinositol moiety. TSA-1 is transcriptionally active at various levels in all organs examined, suggesting that its role is not solely intrathymic. TSA-1 shares amino acid sequence homology to the mouse Ly6 multigene family, epidermal growth factor-like receptors, and to cobra venom neurotoxin. The Tsa-1 locus is located on chromosome 15 linked to Ly6 on the mouse genome. We also examined the effects of MTS 35 in fetal thymic organ cultures repopulated with two subsets of thymocytes representing defined stages of T cell development. Our results suggest that TSA-1 may play a role during positive selection and the transition from CD4+CD8+ thymocytes to the mature CD4+CD8- and CD4-CD8+ subsets.

Amino Acid Sequence↗
PubMed1993

A lymphostromal molecule, thymic shared Ag-1, regulates early thymocyte development in fetal thymus organ culture.

Previously, we detailed the characterization of thymic shared Ag-1, a unique marker of immature thymocytes and isolated thymic stromal cells, defined by the mAb MTS 35. In this study, the functional relevance of this molecule to thymopoiesis was investigated by the addition of purified MTS 35 to fetal thymus organ culture. It down-regulated thymic shared Ag-1 expression and dramatically reduced thymocyte cell yield through inhibition of alpha beta-TcR+ T cell differentiation, post CD3-CD4-CD8- triple negative thymocytes. These effects were specific for the mAb MTS 35, because controls, which include both isotype-matched and other lymphostromal mAb, showed no similar effects. These results demonstrate that thymic shared Ag-1 is a functionally important marker of early thymocyte differentiation, particularly with regard to the alpha beta-TcR lineage.

Animals↗
PubMed1993

Development in the thymus: it takes two to tango.

Intrathymic T-cell development is dependent upon signals provided by the thymic stromal cell microenvironment. However, loss of thymic T cells in natural and experimentally induced situations is associated with a reduction in the surrounding epithelium, suggesting an interdependence between thymocytes and their microenvironment. Here, the authors review the evidence in favour of this intrathymic symbiosis, and hypothesize that T cells may provide maturation and survival signals that are necessary for the development and maintenance of their microenvironment.

Animals↗
PubMed1993

Comparison of three self-applied topical fluoride preparations for control of decalcification.

The purpose of this study was to compare the effectiveness of a 1100 ppm fluoride toothpaste used alone, or together with a 0.05% NaF rinse used once daily or a 0.4% SnF2 gel applied twice daily, in controlling the decalcification that often accompanies orthodontic treatment. Ninety-five consecutively treated adolescent patients were matched for age and sex and assigned to one of these three regimens. Single blind assessments of decalcification were performed on all labial surfaces of all erupted teeth before appliances were placed and 3 months after appliances were removed. Because the first molars had the highest decalcification scores, data for the whole mouth and for first molars were analyzed separately. When pre-treatment levels of decalcification were subtracted from post-treatment values, significantly lower decalcification scores (p < 0.05) were found for both whole mouth and first molars in the rinse and gel groups as compared with the control group (toothpaste alone). Although the gel group consistently had less decalcification than the rinse group, this difference only approached statistical significance. These results indicate that twice daily use of a 1100 ppm fluoride toothpaste and either a once-daily 0.05% NaF rinse or a twice-daily 0.4% SnF2 gel provides additional protection against decalcification beyond that achieved with toothpaste alone.

Adolescent↗
PubMed1993

Characterization of thymic nurse-cell lymphocytes, using an improved procedure for nurse-cell isolation.

Thymic nurse cells (TNC), multicellular complexes consisting of lymphoid cells enclosed within cortical epithelial cells, were isolated from mouse thymus by a modified procedure allowing immunofluorescent labeling and flow cytometric analysis of their lymphoid contents (TNC-L). Collagenase was the only protease used for tissue digestion, to ensure that surface antigen markers remained intact. Zonal unit-gravity elutriation was used to enrich the TNC on the basis of their high sedimentation rate, followed by immunomagnetic bead depletion to remove residual mononuclear cell contaminants and a density separation to remove debris. The TNC-L were then released from inside TNC by a short period of culture. The measured contamination of TNC-L with exogenous thymocytes was around 0.5%. Three-color immunofluorescent labeling revealed that TNC-L included, as well as a majority of immature CD4+8+3low thymocytes, about 12% of apparently mature CD4+8-3high and CD4-8+3high thymocytes. TNC are located in the cortex, where mature cells are rare; the occurrence of mature phenotype cells within these structures suggests that they represent a microenvironment for the selection and generation of mature T cells.

Animals↗
PubMed1993

Phenotypic mapping of the chicken embryonic thymic microenvironment developing within an organ culture system.

The chicken thymic microenvironment, as it developed in an embryonic thymus organ culture system, was phenotypically mapped using a panel of mAb defining both epithelial and nonepithelial stromal cell antigens. We have previously reported that thymocyte proliferation and differentiation with proceed for up to 6-8 days in thymus organ culture, hence demonstrating the functional integrity of the thymic microenvironment in vitro. During this time, the stromal component reflected that of the normal embryo with cortical and medullary epithelial areas readily identifiable by both morphology and surface-antigen expression. An abundance of subcapsular and cortical epithelial antigens was detected in the cultured thymus, particularly those normally expressed by the epithelium lining the capsule, trabeculae, and vascular regions (type I epithelium) in the adult and embryonic thymus. Medullary epithelial antigens developed in organ culture, although were present in lower frequency than observed in the age-matched embryonic thymus. MHC class II expression by both epithelial and nonepithelial cells was maintained at high levels throughout the culture period. With increasing time in culture, the ratio of epithelial to nonepithelial cells decreased, concurrent with a decrease in thymocyte frequency and suggestive of a bidirectional interaction between these two cell types. Thus, a functionally intact thymic microenvironment appears to be maintained in embryonic thymus organ culture, a model that is currently being exploited to assess the role of stromal antigens, as defined by our mAb, in the process of thymopoiesis.

Animals↗
PubMed1992

Treatment of fetal thymic organ culture with IL-1 leads to accelerated differentiation of subsets of CD4-CD8- cells.

Using fetal thymic organ culture (FTOC), we describe the effects of IL-1 on T cell differentiation, particularly within the CD4-CD8- subset. While treatment of FTOC with IL-1 led to a modest reduction in total thymocyte yield, it induced an increase in the percentage of CD4-CD8- cells that express IL-2R early in culture and a decrease in the number of their precursors (CD44+IL-2R- cells). The increase in the percentage of cells expressing IL-2R was not accompanied by an increase in the number of these cells. At later time points these IL-2R+ cells (and their precursors) were reduced relative to controls. The total number of CD4-CD8-CD3- precursor cells in IL-1-treated cultures was reduced to approximately half that in controls at Day 12 of culture. However, only minor inhibition of total cell number was observed, which, taken together with the greater frequency of IL-2R+ precursors, suggests that this depletion of the pool of precursors may have been due to the induction of premature differentiation rather than to its inhibition.

Animals↗
PubMed1992

Thymic shared antigen-1. A novel thymocyte marker discriminating immature from mature thymocyte subsets.

In a previous study, we raised a mAb (MTS 35) reacting with a plasma membrane Ag expressed on both cortical thymocytes and a subset of thymic medullary epithelial cells. In view of the shared expression of this molecule, we have defined it as thymic shared Ag-1 (TSA-1). Considering its selective reactivity with cortical, but not medullary thymocytes, the relevance of TSA-1 as a marker of immature T cells was investigated in detail in this study, using multicolor flow cytometric analysis. TSA-1 was found on all immature thymocyte subsets (CD3-4-8-, CD3-4+8-, CD3-4-8+, CD3-4+8+, CD3low4+8+). Conversely, CD3high4+8- and CD3high4-8+ thymocytes, early thymic migrants and peripheral T cells were TSA-1-. More refined gating and analysis of the transitional CD3intermediate/high4+8+ thymocytes, proposed candidates for negative selection, demonstrated that approximately one half were TSA-1-. In fact, there was a directly inverse relationship between TSA-1 and CD3 expression on thymocytes. In the periphery, TSA-1 was detected on B lymphocytes. TSA-1 is PI-linked and has a molecular mass of 17 kDa nonreduced, or 12 to 13 kDa reduced. Through cross-correlation analysis, this molecule was distinct from H-2K, PNA-R, CD5, CD11a/18, Thy-1, HSA, Ly6A/E, Ly6C, ThB, CD25, CD44. Hence TSA-1 appears to be a unique marker which exquisitely separates mature from immature thymocytes.

Animals↗
PubMed1992

Kinetics of chicken embryonic thymocyte development in ovo and in organ culture.

Thymocyte development was monitored in an embryonic thymus organ culture system to establish a model in the chicken in which the functional nature of the thymic microenvironment could be assessed. Thymus lobes were removed from 10-day-old embryos and cultured for 2-10 days. Cell yield increased to a maximum in 4-8 days of culture with a corresponding decrease in average cell size. An initial thymocyte population of predominantly CD3-CD4-CD8- cells gave rise to all CD3/CD4/CD8-defined subpopulations in vitro, maintaining high levels of CD3-CD4-CD8+ and CD3+CD4-CD8+ cells and a low representation of CD3-CD4+CD8-, CD3+CD4+CD8-, CD3-CD4+CD8+ and CD3+CD4+CD8+ thymocytes. This is the first observation of a CD3-CD4+CD8- population in the chicken. Developmental kinetics of CD3+ cells were similar to that in the embryo, suggesting that the in vitro environment is sufficient to promote and maintain thymocyte maturation. Thymocytes of both the gamma delta and alpha beta T cell receptor (TcR) lineages developed in that order, confirming in ovo data and the lineage potential of the first wave of thymocyte precursors. One unusual finding was a relative accumulation of gamma delta TcR+ thymocytes in culture, incorporating all CD4/CD8 subsets, including a previously undetected population, CD4+CD8-. This may indicate a favorable developmental environment or simply a lack of normal cellular emigration. A detailed comparison with T cell development in the embryo demonstrated that the chicken thymus organ culture system reflects thymic events in ovo during a limited time period and thus should prove useful in the identification of functionally relevant thymic molecules.

Animals↗
PubMed1992

Avian scleroderma: evidence for qualitative and quantitative T cell defects.

T cell activation is dependent upon calcium influx and protein kinase C activation, with subsequent lymphocyte proliferation dependent upon IL-2. Abnormalities in T cell proliferation, including abnormal calcium influx and defective protein kinase C activation, have been identified in aged mice and humans and many autoimmune diseases including diabetes, lupus and scleroderma. Since UCD line 200 chickens, which spontaneously develop a scleroderma-like disease, have both thymic defects and a diminished peripheral blood lymphocyte response to IL-2, we have further investigated T cell function in these birds. Interestingly, line 200 T cells respond poorly in vitro to a variety of diversely acting T cell mitogens including concanavalin A, phytohemagglutinin and anti-chicken CD3 monoclonal antibody. Moreover, they do not respond well even to phorbol myristate acetate in conjunction with ionomycin. Addition of exogenous IL-2-containing supernatant concurrently with mitogenic stimulation also had no significant effect. Analysis of intracellular free calcium demonstrated that the lymphocytes from diseased birds had a reduced influx of calcium (or release for intracellular stores) following stimulation. These data clearly reflect a unique defect in T cell activation associated with avian scleroderma. Analysis of chicken CD3, CD4 and CD8 expression revealed a 39% decrease in peripheral blood CD4+ cells in scleroderma birds, although this decrease was not sufficient to explain the 80-90% decrease observed in proliferation assays and calcium influx. Our data support the hypothesis that avian scleroderma is mediated via abnormal function of lymphocyte co-stimulatory molecules or intracellular calcium regulators.

Animals↗
PubMed1992

Periodontal considerations in the use of bonds or bands on molars in adolescents and adults.

This longitudinal study compared the periodontal status of bonded and banded molars in 20 adult and 40 adolescent patients before, during and after treatment with fixed orthodontic appliances. Plaque accumulation (measured by the Plaque Index), gingival inflammation (measured by the Gingival Index and the bleeding tendency), and pocket depth were assessed by one examiner at sites along the mesio-buccal line angle of the maxillary right first molar and the mandibular left first molar. Assessments were made immediately prior to the placement of fixed appliances (pretreatment), at 1, 3, 6, 9, 12 and 18 months after appliances were placed; and 3 months after appliances were removed (posttreatment). Loss of attachment between the pretreatment and posttreatment visits also was determined. At pretreatment, no significant differences were found in gingival inflammation between maxillary and mandibular banded and bonded molars. During treatment, both maxillary and mandibular banded molars showed significantly (p less than 0.05) greater gingival inflammation and plaque accumulation than did bonded molars. Three months after appliance removal, the maxillary molars that had been banded continued to show significantly more gingival inflammation and loss of attachment than did the maxillary molars that had been bonded. When all banded and bonded teeth were grouped by patient age, mean values for plaque accumulation and gingival inflammation in the maxillary molar regions were significantly greater for adolescents than for adults.

Adolescent↗
PubMed1992

Delineation of chicken thymocytes by CD3-TCR complex, CD4 and CD8 antigen expression reveals phylogenically conserved and novel thymocyte subsets.

To further define the relationship between thymocyte subsets and their developmental sequence, multi-parameter flow cytometry was used to determine the distribution of the CD3-TCR complex and the accessory molecules CD4 and CD8 on chicken thymocytes. As in mammals, adult thymocytes could be subdivided into CD3-, CD3lo, and CD3hi staining populations. CD4 and CD8 distribution on such populations revealed the presence of CD3-CD4+CD8- and CD3-CD4-CD8+ thymocytes, putative precursors to CD4+CD8+ cells, detectable in the adult and at high frequency during ontogeny. Of particular interest was the existence of CD3lo expression on CD4+CD8- and CD4-CD8+, and in some instances, on CD4-CD8- thymocytes. Such phenotypes are not easily detectable in the mammalian thymus but were readily observed in both adult and embryonic chicken thymus from 16 days of embryogenesis. Further analysis of the TCR lineage of these CD3lo cells revealed that they were essentially all of the alpha beta TCR type. Mature CD3hi thymocytes were found within the CD4+CD8+ and CD4+CD8- and CD4-CD8+ subsets. Both alpha beta and gamma delta TCR lineage thymocytes were detected within all CD4- and CD8-defined subsets, thus identifying novel thymocyte subsets in the chicken thymus, namely alpha beta TCR+CD4-CD8- and gamma delta TCR+ CD4+CD8- cells. Hence, this analysis of chicken thymocytes, while confirming the phylogenically conserved nature of the thymus, has revealed novel T cell subsets, providing further insight into the complexity of mainstream thymocyte maturation pathways.

Animals↗
PubMed1992

Five novel antigens illustrate shared phenotype between mouse thymic stromal cells, thymocytes, and peripheral lymphocytes.

Previously we characterized by immunohistology a group of rat anti-mouse thymic stromal mAbs (MTS 12, 32, 33, 35, and 37), which recognized novel plasma membrane determinants on both thymic stromal cells (TSCs) and thymocytes. The present study investigates in more detail this incidence of shared phenotype by an extensive flow cytometric analysis of MTS mAb reactivity on TSCs, thymocyte subsets, peripheral lymphocytes, and bone marrow cells. Examination of freshly isolated or cultured heterogeneous TSCs and TSC clones confirmed that the mAb identified plasma membrane molecules on distinct subsets of these cells. All but MTS 12 reacted with epithelial cells. Triple-labelling illustrated that MTS 32, 33, and 37 were also reactive with more than 90% of total thymocytes, but varied in their distribution on the four major CD4 and CD8 defined subsets. MTS 12, staining with thymic vascular endothelium by immunohistology, labelled more than 95% of each subset. MTS 35 reactivity in each subset correlated strongly with only the immature populations. Examination of peripheral lymphocytes by triple- and double-labelling unexpectedly showed that MTS 33, 35, and 37 did not recognize peripheral T cells but labelled all B cells. MTS 32 was negative for B cells, but positive for all CD8+ T cells, yet only a subset of CD4+ T cells. Further, MTS 33, 35, and 37 were present on a significant percentage of bone marrow cells. MTS 12 reacted with virtually all peripheral T and B cells, and about 50% bone marrow leukocytes. Collectively these results reveal the same novel epitopes on different thymic cell types and subsets thereof, highlighting specific similarities between cells of apparently diverse lineages. These findings may be of importance in the delineation of intercellular communications within the thymus and emphasize the integrated nature of the microenvironment in this organ.

Animals↗
PubMed1992

Comparison of a subgingivally placed cannula oral irrigator tip with a supragingivally placed standard irrigator tip.

This study compared the depth of irrigation of periodontal pockets achieved by a cannula subgingival irrigator tip and a standard oral irrigator tip. They were tested on periodontally involved teeth recommended for extraction from 17 patients. Before extraction, reference grooves were made circumferentially in each study tooth at the level of the gingival margin. In one group of 5 patients (29 teeth), a cannula was inserted halfway into the pocket at the facial, mesiofacial, distofacial, lingual, mesiolingual and distolingual surfaces and the surface irrigated for 5 s at 5 psi with a solution of plaque-staining dye from an oral irrigator. A 2nd group of 7 patients (29 teeth) was tested similarly with a standard irrigating tip at 80 psi. A 3rd (control) group of 5 patients (26 teeth) rinsed with the dye solution. Teeth were then extracted. The distance on each tooth from the reference notch to the apical extent of the stained plaque, and also to the coronal limit of the connective tissue attachment, was measured at 4 sites (mesial, distal, buccal, lingual) under a dissecting microscope to determine the extent of dye penetration. Mean linear penetration for the control group was only 0.1 mm. Irrigation with the cannula tip penetrated farther into both the medium (3.5-6 mm) and the deep (greater than 6 mm) periodontal pockets (p less than 0.01) than did irrigation with the standard tip.(ABSTRACT TRUNCATED AT 250 WORDS)

Catheterization↗
PubMed1992

Phenotypic analysis of the chicken thymic microenvironment during ontogenic development.

The development of monoclonal antibodies (mAb) reactive with the thymic microenvironment has identified distinct subpopulations within the stromal component, but the function of these subregions in intrathymic T-cell differentiation remains essentially an enigma. In this study, we have used such a panel of mAb to examine the chicken thymus during ontogenic development to gain insight into the contributions of these thymic regions to the distinct phases of T-cell development and to further characterize the development of this organ. Our reagents have demonstrated the complex differentiation of the primitive endodermal epithelium into more specialized structures and the development of other thymic stromal components from mesectodermal cells. We also describe molecules localized to the subcapsular and perivascular regions, which have an ontogenic expression corresponding to the early localization and stimulation of thymic precursors and another molecule on the medullary vasculature expressed corresponding to the exit of mature cells from the thymus. In addition, two markers of distinct medullary epithelial clusters are initially expressed corresponding to the appearance of T-cell receptor-1 (TcR-1) and TcR-2 positive cells in the medulla, respectively. These mAb potentially represent excellent reagents for further definition of the thymic modulation of T-cell differentiation.

Age Factors↗
PubMed1992

Phenotypic characterization of chicken thymic stromal elements.

Phenotypic profiles of the thymic stromal components provide an excellent approach to elucidating the nature of the microenvironment of this organ. To address this issue in chickens, we have produced an extensive panel of 18 mAb to the thymic stroma. These mAb have been extensively characterized with respect to their phenotypic specificities and reveal that the stromal cells are equally as complex as the T cells whose maturation they direct. They further demonstrate that, in comparison to the mammalian thymus, there is a remarkable degree of conservation in thymic architecture between phylogenetically diverse species. Eleven mAb reacted with thymic epithelial cells: MUI-73 was panepithelium, MUI-54 stained all cortical and medullary epithelium but only a minority of the subcapsule, MUI-52 was specific for isolated stellate cortical epithelial cells, MUI-62, -69, and -71 were specific for the medulla (including Hassall's corpuscle-like structures), MUI-51, -53, -70, and -75 reacted only with the type-1 epithelium, or discrete regions therein, lining the subcapsular and perivascular regions and MUI-58 demonstrated the antigenic similarity between the subcapsule and the medulla. Seven other mAb identified distinct isolated stromal cells throughout the cortex and medulla. Large thymocyte-rich regions, which often spanned from the outer cortex to medulla, lacked epithelial cells. These mAb should prove invaluable for determining the functional significance of thymic stromal-cell subsets to thymopoiesis.

Animals↗
PubMed1992

Two-year longitudinal study of a peroxide-fluoride rinse on decalcification in adolescent orthodontic patients.

The purpose of the present study was to determine if once daily use of a 1.5% H2O2 rinse with 0.05% NaF was more effective in preventing decalcification in adolescent orthodontic patients than comparable use of a 0.05% NaF rinse without H2O2, or in patients using no rinse at all. Ninety-five subjects were selected consecutively from adolescents scheduled to receive fixed orthodontic treatment on both dental arches. Three groups were formed that were matched in percentages for age and sex. The first group (control group, n = 35) used a 1100 ppm F toothpaste only. The second group (NaF rinse group, n = 30) used both the same toothpaste and a once daily 0.05% NaF rinse. The third group (H2O2-NaF rinse group, n = 30) used the toothpaste and a once daily rinse containing both 0.05% NaF and 1.5% H2O2. Decalcification was assessed single-blind on the facial surfaces of all erupted teeth at baseline (before appliances were placed), and 3 months after fixed appliances were removed. The difference between baseline and post-treatment decalcification levels determined the incidence of decalcification during orthodontic treatment. Since the first molars were found to have the highest decalcification scores, separate analyses of variance were carried out for the whole mouth and first molar assessments. A p value of less than 0.05 was considered statistically significant. The results showed no significant differences between any of the groups before orthodontic treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗