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Biomedical subjects

W C Davis

Publications and source records attributed to W C Davis.

At least 109 records · Page 6Linked to original sources
PubMed1995

Expression of the pim-1 protooncogene: differential inducibility between alpha/beta- and gamma/delta-T cells and B cells.

The pim-1 gene encodes a serine/threonine protein kinase with expression restricted primarily to cells of hematopoietic lineage and is thought to play a role in the signal transduction events associated with lymphocyte activation. A rapid increase in pim-1 mRNA levels was found after stimulation of normal unseparated PBMCs with phorbol ester (PMA) and a calcium ionophore (ionomycin) with the peak level occurring 4 hr poststimulation. Treatment of PBMCs with ionomycin alone caused only a minimal increase in pim-1 mRNA, whereas treatment with PMA alone induced a large increase in pim-1 mRNA, suggesting that the activation of a signaling pathway involving protein kinase C is responsible for the accumulation of this transcript. In enriched subpopulations of resting alpha/beta-T cells, gamma/delta-T cells, and B cells, pim-1 expression was found to be constitutively expressed, albeit at lower levels in T cells. This basal level of pim-1 expression could be increased by stimulation of alpha/beta-T cells (approx fivefold) and gamma/delta-T cells (approximately sevenfold) with PMA plus ionomycin. In contrast, pim-1 expression was not inducible in B cells. In PBMCs, half-life determination studies showed that turnover of pim-1 mRNA was markedly prolonged as a result of message stabilization induced by PMA plus ionomycin treatment. In addition, stable pim-1 transcripts were also observed in all transformed lymphoid cell lines examined. Taken together, these results suggest that the stability of pim-1 transcripts may be linked to the regulation of cell growth and represent the first direct demonstration that pim-1 expression is indeed regulated in a cell-type-specific manner.

Animals↗
PubMed1995

Expression of gamma delta T cell receptor on caprine globule leukocytes.

Histochemical characteristics and immunological surface phenotypes of globule leukocytes (GLs) of normal goats were investigated in the intestine. In the small intestine, GLs were concentrated in the base of the villus and around the crypt, whereas in the cecum and colon they were randomly distributed. Their cytoplasmic granules exclusively stained with phosphotungstic acid hematoxylin, and were negative for peroxidase and histamine in contrast to those of subepithelial mast cells. The existence of chondroitin sulfate in some granules of GLs and heparin in most granules of mast cells were revealed by alcian blue staining and digestion with chondroitinase ABC. Isolated intestinal GLs were positive for T cell receptor (TcR) 1-N24 (gamma delta) and CD8 alpha, and negative for WC1-N3 and WC1-N4. Cryostat sections of ileum revealed preferential intraepithelial distribution of both TcR1-N24+ cells and CD8+ cells. WC1-N3+ and WC1-N4+ cells were rarely seen in the epithelium and lamina propria. These results indicate that caprine GLs are a gamma delta T cell subset, which is a different cell population from WC1 positive gamma delta T cells.

Animals↗
PubMed1995

Up-regulation of IL-2 receptor alpha and MHC class II expression on lymphocyte subpopulations from bovine leukemia virus infected lymphocytotic cows.

Infection with bovine leukemia virus (BLV) leads to a persistent lymphocytosis (PL) characterized by a marked increase in circulating B lymphocytes that express the orthologue of CD5. To gain insight into the factors accounting for lymphocytosis, experiments were conducted to determine the functional activation status of lymphocytes from BLV seronegative and BLV infected aleukemic cows with PL. Stimulation with the B lymphocyte mitogen Staphylococcus aureus Cowan strain I (SAC), recombinant human interleukin-2 (rIL-2), or pokeweed mitogen (PWM), a T lymphocyte-dependent B lymphocyte mitogen, revealed differences in the pattern of expression of IL-2 receptor alpha (IL-2R alpha) and major histocompatibility (MHC) class II molecules on B and T lymphocytes from uninfected and BLV infected PL cows. rIL-2 induced expression of IL-R alpha on B lymphocytes from PL cows but not B lymphocytes from BLV seronegative cows. SAC alone, or in combination with rIL-2, had no effect on B lymphocytes from BLV seronegative cows. However, rIL-2 alone or in combination with SAC induced expression of IL-2R alpha on B lymphocytes from PL cows. PWM stimulated expression of IL-2R alpha on bovine B lymphocytes regardless of BLV status, and induced a significantly higher level of expression on B lymphocytes from PL cows. Mitogens and rIL-2 had a similar stimulatory effect on induction of IL-2R alpha expression on CD4 T lymphocytes regardless of BLV status. Only PWM induced expression of IL-2R alpha on bovine CD8 T lymphocytes and induced a significantly higher level of expression on this T lymphocyte subset from PL cows. Examination of freshly isolated B lymphocytes from PL cows revealed increased spontaneous expression of the MHC class II molecule compared to B lymphocytes from control cows. None of the culture conditions examined induced MHC-II expression on CD4 and CD8 T lymphocytes from BLV seronegative cows. In contrast, SAC+IL-2 and PWM induced MHC-II expression on CD4 and CD8 T lymphocytes from BLV infected PL cows, resulting in a significantly greater proportions of these lymphocyte subsets expressing this molecule compared to CD4 and CD8 T lymphocytes from control cows. The data indicate that infection with BLV affects the response of B and T lymphocytes to signals of activation, up-regulating the expression of surface molecules involved in both direct contact and cytokine-mediated T lymphocyte-dependent B lymphocyte activation.

Animals↗
PubMed1995

The behaviour of monoclonal antibodies in the First International Pig CD Workshop reacting with gamma delta/Null T lymphocytes in the blood of SLAb/b line pigs.

Further studies were carried out on the monoclonal antibodies (mAbs) from the First International Swine CD Workshop which react with gamma delta Null T-lymphocytes, defined by the binding of mAb w020/141 (MAC320) as Swine Workshop Cluster number SWC6. Studies were also carried out on several other mAbs from the same workshop which identify other CD antigens, but whose binding is not restricted exclusively to gamma delta Null T-lymphocytes. The first group consists of 11 mAbs (w021, w022, w059-w065, w105 and w117) and the second group of 18 mAbs (w008, w026, w056, w067-w071, w080, w091-w094, w110, w111, w118, w119 and w121). All mAbs were characterised by binding to peripheral blood lymphocytes (PBL) from normal, sham-thymectomized (STx) and thymectomized (Tx) pigs of the Babraham SLAb/b line and by their overlap, using two-colour immunofluorescence with biotinylated mAb MAC320 (w020/141), which identifies all gamma delta Null cell T-lymphocytes and the Null cell subpopulation identified by MAC319 (w021). The Null cell-specific mAbs were also used in inhibition studies of MAC319 and MAC320 binding and by staining PBL with pairs of mAbs together with either MAC319 or MAC320. Based on these data we suggest a putative relationship of the Null cell subsets defined by these mAbs with each other.

Animals↗
PubMed1995

A highly stable and selective biosensor using modified nicotinic acetylcholine receptor (nAChR).

Methods for developing stable, sensitive and selective bilayer lipid membrane (BLM)-based biosensors are discussed. Stable BLMs were formed over micromachined polyimide apertures. Selective sensors were made by incorporating nicotinic acetylcholine receptors (nAChRs) modified with bispecific antibodies (BsAbs). When two BsAbs, attached to one nAChR, encounter antigen (Ag), channels are blocked. Sensitivity to single Ag molecules would be possible by monitoring closure of individual nAChRs.

Animals↗
PubMed1995

Conserved recombinant antigens of Anaplasma marginale and Babesia equi for serologic diagnosis.

The competitive inhibition ELISA (CI-ELISA) format overcomes problems associated with antigen purity since the specificity of the CI-ELISA depends solely on the monoclonal antibody (mAb) used. Therefore, the CI-ELISA format is well suited for use with recombinant antigens. Molecular clones expressing a conserved 19 kDa protein of Anaplasma marginale and a 34 kDa protein of Babesia equi were derived and characterized. The 19 kDa A. marginale protein, conserved in all recognized Anaplasma species, and present in the infected tick salivary gland, was reactive with all bovine immune sera tested. The 34 kDa B. equi protein contains a protein epitope bound by antibody in equine immune sera from 19 countries. Monoclonal antibodies reactive with these proteins were derived and applied with recombinant copies of the 19 kDa A. marginale and 34 kDa B. equi proteins in a CI-ELISA format.

Amino Acid Sequence↗
PubMed1995

Biochemical and phenotypic characterization of the ovine beta 2 (leucocyte) integrins.

This paper is concerned with the relationship of the three distinct members of the ovine beta 2-integrin family of leucocyte adhesion molecules that play an important role in cell-cell and cell-matrix interactions. A panel of monoclonal antibodies (mAbs) specific for sheep and cattle macrophages was characterized by flow cytometry, immunohistology, and immunoprecipitation for reactivity to the beta 2 integrins. Immunoprecipitation analysis of sheep antigens showed that these monoclonal antibodies could be divided into four distinct groups. All precipitated an M(r) 95,000 beta chain but they differed in the size or number (or both) of the alpha chains recognized. Group 1 precipitated alpha chains of M(r) 180,000; group 2 had M(r) 170,000 alpha chains; the group 3 alpha chain was of M(r) 150,000 and group 4 mAbs precipitated alpha chains of all three sizes. The relationship between these antibodies was demonstrated by sequential immunoprecipitation, which showed that the reactivities of antibodies in groups 1, 2 and 3 were mutually exclusive but that group 4 antibodies shared a common specificity with the other three groups. By analogy with the human and murine beta 2 integrin families, group 1 antibodies seemed to be specific for CD11a (LFA-1); group 2 were CD11b (CR3 or Mac1); group 3 were CD11c (CR4 or p150/95) and group 4 were CD18. In addition to different molecular weights, these antibodies had different cellular and tissue distributions. CD11a and CD18 were distributed identically. The antigens recognized by both were present on all the leucocyte populations. The mAbs recognizing CD11b reacted with a sub-population of peripheral blood B lymphocytes and all myeloid cells (alveolar macrophages, peripheral blood monocytes and granulocytes) except afferent lymph dendritic cells (ADC). Anti-CD11c (p 150/95 or CR4) antibodies reacted strongly with macrophages and ADC but were weakly reactive on monocytes and negative on neutrophils. CD11c was also present on a sub-population of peripheral blood B cells.

Animals↗
PubMed1995

Identification and characterization of the major proteins of malignant catarrhal fever virus.

Malignant catarrhal fever virus (MCFV), a gamma-herpesvirus, causes a severe inflammatory and lymphoproliferative disease of cattle and other susceptible ruminants. Polyclonal antisera and monoclonal antibodies (MAbs) to the Minnesota isolate of MCFV were produced and used to examine the characteristics of the viral proteins. Immunoprecipitation of antigens of the Minnesota isolate of MCFV with polyclonal antisera revealed at least 11 proteins with molecular masses ranging from 17 kDa to 145 kDa. Among 279 candidate anti-MCFV hybridomas, 14 were selected and clustered into six groups on the basis of the patterns of reactivity to viral proteins in immunoprecipitation and immunoblot. The group I MAbs exhibited strong neutralizing activity and recognized a glycosylation-dependent conformational epitope on a 110 kDa protein. The MAbs in group II bound a non-neutralizing conformational epitope on a 130 kDa non-glycosylated protein. A glycosylated protein complex of 115/110/105/78/45 kDa moieties was identified by the MAbs in group III. The MAbs in groups IV, V and VI reacted with non-glycosylated proteins of 36/34 kDa, 24 kDa and 17 kDa, respectively. Comparison of three MCFV isolates [the Minnesota isolate, the Austrian isolate (Au-732) and the African prototype isolate (WC-11)] revealed no apparent differences in immunoprecipitation patterns with the single exception that the 110 kDa protein of WC-11 was slightly smaller than its counterpart in the Minnesota isolate.

Animals↗
PubMed1995

Immunohistologic studies on subpopulations of lymphocytes in cattle with enzootic bovine leukosis.

The distribution of subpopulations of lymphocytes in lymph nodes and tumors from cattle with enzootic bovine leukosis (EBL) was examined by immunohistochemistry using a panel of monclonal antibodies against leukocyte differentiation molecules of EBL. The lesions in lymph nodes could be divided into three types based on the extent of infiltration and proliferation of neoplastic cells with provirus and differential expression of leukocyte differentiation molecules. The number of B-B2+, sIgM+ cells was reduced in frequency in follicles during the neoplastic cell proliferation. CD4- and CD8-positive alpha/beta T cells and gamma/delta T cells positive for WC1 (workshop cluster designation) were also reduced in frequency in areas infiltrated with neoplastic cells. Almost all neoplastic cells were B-B2- and IgM-positive. However, there were a few B-B2- and/or IgM-negative cells or cells stained faintly in all cases. WC1+ cells were not observed in tumor tissues. However, CD4+ and CD8+ cells were observed throughout tumor tissues, suggesting a role for these cells in tumor immunity.

Animals↗
PubMed1995

Phenotypic analysis of neoplastic cells from calf, thymic, and intermediate forms of bovine leukosis.

Immunohistochemistry and flow cytometric analysis were used with monoclonal antibodies to examine the phenotype of neoplastic cells from cattle with sporadic bovine leukosis (three cases of calf form, two cases of thymic form, and three cases of intermediate form). Three cases of calf form and two cases of intermediate form were positive for B cell lineage in immunohistologic examination and in flow cytometric analysis for B-B2+, sIgM+, and major histocompatibility class II+. Two cases of thymic form and one case of intermediate form were CD2+, CD5+, CD6+, and CD8+ in immunohistologic examination and in flow cytometric analysis. The results show that neoplastic cells develop from B and T cell lineages in sporadic bovine leukosis.

Animals↗
PubMed1995

A novel BoLA class II molecule with a tissue distribution different from BoLA-DR or BoLA-DQ molecules.

This study was designed to investigate the lymphoid tissue distribution of a new BoLA class II molecule defined by a unique monoclonal antibody H42A. We immunostained various lymphoid organs of 4-month-old Holstein calves with this monoclonal antibody and compared its tissue distribution to the BoLA-DR and BoLA-DQ expressions. Our results demonstrate a unique tissue distribution of the H42A-defined molecules, restricted to epithelial cells of the thymic medulla but extending in the periphery to the different cells involved in antigen presentation (B-cells, macrophages and dendritic cells). The peculiar distribution of this new BoLA class II molecule suggests that it has a specific function.

Animals↗
PubMed1995

Peripheral blood and synovial fluid mononuclear cell phenotypes in lentivirus induced arthritis.

OBJECTIVE: To identify the phenotypes and activation status of peripheral blood (PB) and synovial fluid (SF) mononuclear cells associated with caprine arthritis encephalitis virus (CAEV) induced arthritis in goats. METHODS: PB and SF mononuclear cells from 8 goats chronically infected with CAEV and 2 mock-infected goats were phenotyped by single immunofluorescence flow cytometry using a panel of monoclonal antibodies (Mab) to caprine leukocyte differentiation molecules. The activation status of mononuclear cell subsets was evaluated by dual immunofluorescence flow cytometry using Mab to major histocompatibility complex (MHC) class II molecules and the interleukin 2 receptor (IL-2R). RESULTS: Three CAEV infected goats had chronic progressive arthritis, clinically evident by periarticular swelling of carpal joints with excessive SF containing inflammatory cells and radiographic changes indicating soft tissue swelling and erosion of articular surfaces. The other 5 infected goats and 2 mock-infected control goats did not exhibit criteria of arthritis. The composition of PB mononuclear cells (11.3 +/- 5.0% monocytes, 21.1 +/- 4.7% B cells, 29.6 +/- 5.4% CD4+ cells, 15.2 +/- 6.1% CD8+ cells, and 9.7 +/- 3.9% gamma delta T cells) was not significantly different between mock-infected and CAEV infected goats. In contrast, cells within the SF of arthritic carpal joints consisted of 71.9 +/- 7.9% CD8+ T cells, 13.3 +/- 5.9% CD4+ T cells and < 2% B cells. The proportions of SF macrophages (7.8 +/- 5.2%) and gamma delta T cells (6.5 +/- 1.3%) were not significantly different from PB. All SF mononuclear cells were activated with respect to class II determinants orthologous to HLA-DR, DP and DQ. IL-2R expression by CD4+ and CD8+ T lymphocytes in SF was reduced compared to PB. CONCLUSION: Lymphocytes infiltrating the SF of arthritic carpal joints of CAEV infected goats consisted of a predominant subset of class II activated CD8+ T lymphocytes and a minority population of CD4+ T lymphocytes, both of which express very little IL-2R. These results parallel previous reports of the phenotypes and activation status of mononuclear cells in rheumatoid SF. A potential connection between T lymphocyte subset reactivity to CAEV and immunopathogenesis of arthritis is suggested.

Animals↗
PubMed1995

Immunopathology of chronic lentivirus-induced arthritis.

This study evaluated histopathology and mononuclear cell phenotypes in synovial lesions of chronic arthritis induced by experimental infection of Saanen goats with caprine arthritis-encephalitis lentivirus. Histological examination of carpal joint synovium of three infected goats with clinical arthritis revealed progressive lesions consisting of membrane villus hypertrophy with extensive angiogenesis and mononuclear cell infiltration and degenerative changes of membrane villus necrosis associated with loss of vasculature and infiltrates. Changes in synovial tissue of five age-matched infected goats without clinical arthritis were limited to moderate synovial membrane hyperplasia also noted in an age-matched uninfected goat. Immunohistochemistry identified CD45R+ CD5- B lymphocytes as the principal component of most perivascular infiltrates in arthritic synovium. Other mononuclear cells included perivascular CD4+ and CD8+ T lymphocytes and macrophages with a prominent accumulation of CD8+ T lymphocytes at the lining surface of inflamed villi. T lymphocytes and macrophages as well as synovial lining cells were activated with respect to MHC class II but not for interleukin-2 receptors. Inflamed villi also contained lymphoid aggregates comprised of B cell germinal centers and activated T-cell mantles. B cells expressing immunoglobulin occurred around follicles and throughout inflamed villi. These findings indicate that memory immune responses that favor expansion and maturation of B cells and immunoglobulin production contribute to the immunopathology of chronic arthritis.

Animals↗
PubMed1995

Effects of dexamethasone on cell-mediated immune responses in cattle sensitized to Mycobacterium bovis.

Systemic administration of dexamethasone led to a significant reduction in the size of the tuberculin reaction in response to intradermal injection of bovine purified protein derivative in 18 cattle experimentally sensitized to Mycobacterium bovis (P < 0.01) and 8 cattle naturally infected with M bovis (P < 0.001). The reaction in 6 of the 7 M bovis infected cattle that received dexamethasone was classified as negative for the standard interpretation of the single intradermal comparative tuberculin test. Significantly fewer BoCD2+ (P < 0.05) and BoCD4+ T cells (P < 0.001) were present at the reaction site and in blood of dexamethasone-treated cattle, compared with untreated control cattle. Significantly fewer cells expressing the interleukin-2 receptor and WC1+ gamma delta T cells (P < 0.001), and a significantly greater number of cells expressing the ACT2 antigen (P < 0.05) were found at the reaction site in dexamethasone treated cattle than in controls. The number of BoCD8+ T cells at the reaction site and in blood was not significantly affected by administration of dexamethasone. In vitro production of interferon-gamma by lymphocytes incubated with bovine purified protein derivative also was significantly lower (P < 0.01) in the dexamethasone treated cattle.

Animals↗
PubMed1994

Efficient optimization of ELISAs.

In this paper, we describe a technique for using the statistical method of fractional factorial design in the optimization of an ELISA. Fractional factorial design dramatically reduces the total number of experiments required in the optimization. In addition, this technique enables us to determine the parameters that give the maximum sensitivity range with the most accuracy for the ELISA studied.

Animals↗