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W C Davis

Publications and source records attributed to W C Davis.

At least 163 records · Page 9Linked to original sources
PubMed1993

The DA6-147 monoclonal antibody raised against the HLA-DR alpha chain identifies a cryptic epitope on the BoLA-DR alpha chain.

By combining immunoprecipitation of BoLA molecules with monoclonal antibodies raised against 2 different major histocompatibility class II antigens, TH14B and TH81A, and western blotting using the anti-HLA DR alpha monoclonal antibody DA6-147, we characterized an epitope conserved on BoLA- and HLA-DR alpha chains. This epitope, not accessible on intact cells, was revealed after cell lysis. In addition, these results allowed us to define TH14B as an anti-BoLA-DR monoclonal antibody whereas TH81A, raised against the products of a second MHC locus, is probably an anti-BoLA-DQ monoclonal antibody.

Animals↗
PubMed1992

Immunophenotypic characterization of owl monkey peripheral blood mononuclear cells.

A two-phase study was initiated to delineate the peripheral blood lymphocyte populations present in owl monkeys and to correlate those populations with immune response and parasitism during malaria infection. The goal of phase I of the study was to elucidate a monoclonal antibody panel that could be used to characterize peripheral blood mononuclear cell (PBMC) populations with flow cytometric techniques. Forty-two monoclonal antibodies (reported to be reactive with human and macaque lymphocyte antigens) were screened for activity to owl monkey PBMC. Eleven monoclonals were found to react: anti-H42A (MHC Class II DP-like); anti-TH14B (MHC Class II DR-like); and anti-TH81A5 (MHC Class II DQ-like); anti-H58A (MHC Class I); anti-DH59B (granulocyte and monocyte); anti-B1 (B cell); anti-T4 (CD4); anti-Leu3a (CD4); anti-Leu11a (CD16); anti-60.3 (CD18); and anti-OKM1 (NK and monocyte). In a preliminary retrospective study correlating antibody titers, parasitemia values, and MHC Class I and Class II marker profiles on PBMC to test antigens used in malaria vaccine trials, a significant negative association was observed between cells bearing MHC Class II molecules and the other elements of the comparison. In summary, an appropriate panel of monoclonal antibodies has been identified for characterizing PBMC in owl monkeys, and preliminary studies indicate a possible association between clinical outcome and expressed phenotypic PBMC markers.

Animals↗
PubMed1992

Bovine major histocompatibility complex class I specific monoclonal antibodies characterized by flow cytometry, one- and two-dimensional electrophoresis, western blot and inhibition of cytotoxic T lymphocyte function.

To identify and characterize the bovine major histocompatibility complex (MHC) class I molecules, a panel of 11 monoclonal antibodies (mAbs) were analyzed. The mAbs reacted with bovine MHC class I antigens, as assessed by flow cytometry and immunoprecipitation followed by one- and two-dimensional gel electrophoresis. Analysis by flow cytometry revealed that class I molecules were expressed less on a class I mutant B-lymphoblastoid cell line than on the parent cell line. The relative molecular weights of the proteins identified by these mAbs were similar to those reported previously for cattle and humans. Nonequilibrium pH gradient two-dimensional gel electrophoresis showed that RH16C recognized four different class I gene products, indicating this mAb reacts with a conserved epitope present on different class I molecules. These mAbs effectively blocked cytotoxic T lymphocyte killing of allogeneic lymphoblasts, suggesting the functional importance of beta-2m in this process. These mAbs should be useful reagents for studying bovine MHC class I molecules.

Animals↗
PubMed1992

The cellular immunology of bovine paratuberculosis: the predominant response is mediated by cytotoxic gamma/delta T lymphocytes which prevent CD4+ activity.

Peripheral blood T-cell subsets were obtained from an experimentally sensitized bovine and from nine bovines naturally infected with Mycobacterium paratuberculosis and tested for their ability to respond to antigen. It was determined that following antigen challenge, proliferative responses followed a biphasic pattern: an initial CD4+ proliferative response, a period of anergy, and a final response governed by gamma/delta T lymphocytes. The anergic phase was characterized by a dramatic drop in peripheral blood CD4+ cells; the nature of the non-responsiveness could not be determined. The anergic phase was followed by increased proliferative responses of non-MHC restricted gamma/delta T lymphocytes. Although CD4+ cells had the ability to proliferate in response to M. paratuberculosis antigens in the absence of gamma/delta T cells, antigen-primed CD4+ lymphocytes failed to incorporate [3H]-thymidine in the presence of gamma/delta T cells and M. paratuberculosis antigen. It was concluded that M. paratuberculosis-specific gamma/delta T lymphocytes have immunoregulatory function and exhibit cytotoxic activity against antigen-primed CD4+ helper cells. The data suggest that the inability of effector cell populations to prevent intracellular proliferation of M. paratuberculosis may be a result of cytotoxic killing of the T helper lymphocyte population required for macrophage activation.

Animals↗
PubMed1992

The Anaplasma marginale msp5 gene encodes a 19-kilodalton protein conserved in all recognized Anaplasma species.

Immunization with Anaplasma marginale outer membranes induced immunity against clinical disease which correlated with antibody titer to outer membrane proteins, including a 19-kDa protein (N. Tebele, T. C. McGuire, and G. H. Palmer, Infect. Immun. 59:3199-3204, 1991). This 19-kDa protein, designated major surface protein 5 (MSP-5), was encoded by a single-copy 633-bp gene. The molecular mass of MSP-5, defined in immunoblots by binding to monoclonal antibody ANAF16C1, was conserved among all recognized species of Anaplasma: A. marginale, A. centrale, and A. ovis. Recombinant MSP-5, which absorbed the antibody reactivity of bovine immune serum to native MSP-5, was recognized by anti-A. marginale and anti-A. centrale immune sera in a competitive inhibition assay with monoclonal antibody ANAF16C1. The presence of antibody to the epitope defined by monoclonal antibody ANAF16C1 in all postinfection sera tested indicates that this epitope is a potential diagnostic antigen for use in identifying persistently infected cattle.

Amino Acid Sequence↗
PubMed1992

Transmembrane protein oligomers of caprine arthritis-encephalitis lentivirus are immunodominant in goats with progressive arthritis.

To dissect mechanisms of caprine arthritis-encephalitis lentivirus-induced arthritis, an undefined immunodominant viral glycoprotein, gp90 (G. C. Johnson, A. F. Barbet, P. Klevjer-Anderson, and T. C. McGuire, Infect. Immun. 41:657-665, 1983), was characterized. Monoclonal antibody to gp90 and specific antiserum to env gene products demonstrated that gp90 was a transmembrane protein (TM) dimer. Goats with progressive arthritis had high antibody titers to oligomeric and monomeric (38-kDa) TM.

Animals↗
PubMed1992

A rapid, reliable method of evaluating growth and viability of intraerythrocytic protozoan hemoparasites using fluorescence flow cytometry.

Fluorescence flow cytometry was employed to assess the potential of a vital dye, hydroethidine, for use in the detection and monitoring of the viability of hemoparasites in infected erythrocytes, using Babesia bovis as a model parasite. The studies demonstrated that hydroethidine is taken up by B. bovis and metabolically converted to the DNA binding fluorochrome, ethidium. Following uptake of the dye, erythrocytes containing viable parasites were readily distinguished and quantitated. Timed studies with the parasiticidal drug, Ganaseg, showed that it is possible to use the fluorochrome assay to monitor the effects of the drug on the rate of replication and viability of B. bovis in culture. The assay provides a rapid method for evaluation of the in vitro effect of drugs on hemoparasites and for analysis of the effect of various components of the immune response, such as lymphokines, monocyte products, antibodies, and effector cells (T, NK, LAK, ADCC) on the growth and viability of intraerythrocytic parasites.

Animals↗
PubMed1992

Repeated restraint and isolation stress alters adrenal and lymphocyte functions and some leukocyte differentiation antigens in lambs.

Lambs were used to evaluate the effect of repeated restraint and isolation stress (RIS) on secretion of cortisol, lymphocyte proliferative responses to mitogens, production of interleukin-2, and expression of leukocyte differentiation antigens. Differentiation antigens evaluated included cluster of differentiation antigens 2, 4, and 8 (CD2, CD4, and CD8, respectively); B cells; and major histocompatibility complex (MHC) class II, DQ, and DR. Lambs were assigned to either control (CON; n = 12) or to RIS treatment (n = 12) then were stanchioned in environmentally controlled rooms at 18 degrees C and constant light for 11 d before jugular vein catheters were inserted on d 0 of the experiment. On d 12, 13, and 14, lambs in the RIS treatment were removed to another location, restrained, and isolated from visual and tactile contact with other lambs for 6 h on each day. Following the 6-h stress treatment, lambs were returned to their home stanchions. The CON lambs remained in their stanchions. Samples of serum were obtained from all lambs, beginning before RIS (0 h) and at .5-h intervals until the completion of stress (6 h) on d 12 and 14. In addition, samples of whole blood were obtained at 0 and 6 h on d 12, 13, and 14 for evaluation of immune function characteristics. Fitted polynomial curves describing the cortisol response in RIS and CON lambs differed (P less than .005) on both d 12 and 14, reflecting the unmistakable increase in cortisol in response to the stressor.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Bovine mononuclear leukocyte subpopulations in peripheral blood and mammary gland secretions during lactation.

Florescence flow cytometry and monoclonal antibodies were used to analyze the composition of leukocytes from peripheral blood and mammary gland secretions. Samples were obtained from Holstein dairy cows, free of IMI, at six time points during the lactation cycle. The percentage of monocytes in peripheral blood mononuclear cells varied from 15 to 31%; the lowest percentage occurred at the early nonlactation period. The percentage of T lymphocytes from mammary gland secretions varied from 16% during the periparturient period to 62% at late lactation. The B lymphocytes varied from 7% at late lactation to 25% during the periparturient period. Macrophages varied from 21 to 69%; the highest percentage occurred during the periparturient period. The mean ratio of CD4+:CD8+ T lymphocytes in the peripheral blood and mammary gland secretions was 1.53 and .85, respectively. A subpopulation of activated CD8+ T lymphocytes present in mammary gland secretions throughout the lactation cycle coexpressed a new activation molecule, ACT2. Increases in the proportion of CD8+ T lymphocytes were associated with an increase in the percentage of CD8+, ACT2+ T lymphocytes. Activated CD8+ T lymphocytes may play an important role in the regulation and expression of the local immune response to pathogens.

Animals↗
PubMed1992

Characterization of B-cell phenotypic changes during ileal and jejunal Peyer's patch development in sheep.

Changes in B-cell phenotype during development of ileal and jejunal Peyer's patches (PP) of sheep were investigated using flow cytometry and immunoperoxidase-stained cryosections. On Day 104 of gestation (term at 150 days) B-cell clusters were identified in the lamina propria of the ileum. These clusters were composed of cells that expressed surface IgM (sIgM), lambda or kappa light chain, and BAQ44A, a B-cell differentiation molecule. No cells in the clusters stained for terminal deoxynucleotide transferase. On Day 132 gestation, a change was evident in the phenotype of ileal PP B cells. Most B cells expressed a reduced level of sIgM and 20% were BAQ44A-. The B cells in the dome region were BAQ44A+ but few BAQ44A+ cells were present in the follicles. At 6-8 weeks of age BAQ44A+ cells were restricted to the dome region of the ileal PP; flow cytometric analysis confirmed that 25% of B cells isolated from the dome/follicle complex were BAQ44A+. Thus, the primordial PP was populated with B cells that were phenotypically similar to circulating B cells (sIgMhigh, BAQ44A+). After 132 days gestation, the predominant B-cell phenotype in the ileal PP changed to sIgMlow and BAQ44A-. This phenotypic change could be the result of either early immigrant B-cell differentiation or subsequent colonization by sIgMlow BAQ44A- B cells. The phenotypic changes of ileal PP follicular B cells were not complete until after birth and different phenotypic changes were observed in follicles of the jejunal PP of young lambs.

Animals↗
PubMed1992

An analysis of the growth and differentiation of B cells isolated from follicles of the ileal Peyer's patch of sheep.

We developed a method to isolate and culture cells from the lymphoid follicles of the ileal Peyer's (PP) patch of young sheep (6-12 weeks). These cells were 98% sIgM+ B cells and 1% T cells. Cultured follicular cells were used to investigate B-cell proliferation and differentiation. Less than 50% of B cells were viable after 24 hr of culture and this decrease in B-cell viability also occurred following co-stimulation with pokeweed mitogen (PWM) and recombinant bovine interleukin-1 (rBoIL-1) or rBoIL-2. In contrast, co-stimulation with PWM and either rBoIL-1 or rBoIL-2 induced a marked proliferative response that was maximal on Day 4 of culture. Cytokine-induced proliferation of the B cells required PWM co-stimulation and proliferation induced by rBoIL-1 and rBoIL-2 was neither additive or synergistic. This suggests that PWM bound a molecule or molecules that signalled responsiveness to both rBoIL-1 and rBoIL-2. Culture of follicular cells with PWM and both rBoIL-1 and rBoIL-2 also resulted in B-cell differentiation. This differentiation was associated with decreased proliferation, an increased number of viable B cells, and increased expression of both surface IgM and non-Ig membrane molecules. Thus, co-stimulation of ileal PP follicular cells with PWM and rBoIL-1 and rBoIL-2 resulted in both B-cell proliferation and differentiation.

Animals↗
PubMed1992

Selection of BoCD25 monoclonal antibodies by screening mouse L cells transfected with the bovine p55-interleukin-2 (IL-2) receptor gene.

The bovine interleukin-2 receptor-alpha (IL-2R alpha) gene has been isolated and a rabbit antiserum against a fusion protein of the gene has been produced. However, the antiserum does not inhibit IL-2-dependent proliferation. Since a panel of monoclonal antibodies (mAb) to bovine activation antigens was available, we transfected the gene into mouse L fibroblasts, selected stable transfectants with the rabbit antiserum, and screened for antibodies that bound the transfected cells but not the untransfected cells. Three mAb were selected and all three precipitated a molecule of M(r) 55,000 (under reducing conditions) from activated cells, as expected from homology with mouse and human IL-2R alpha (CD25, Tac). One of the three mAb was a strong inhibitor of IL-2-dependent proliferation of bovine lymphocytes. Thus, the availability of transfected cells allowed us to establish quickly and unequivocally the antigenic specificity of a number of antibodies.

Animals↗
PubMed1991

A flow cytometric method for assessing viability of intraerythrocytic hemoparasites.

We have developed a rapid, reliable method of evaluating growth and viability of intraerythrocytic protozoan hemoparasites. The assay involves the selective uptake and metabolic conversion of hydroethidine to ethidium by live parasites present in intact erythrocytes. The red fluorescence imparted by ethidium intercalated into the DNA of the parasite permits the use of flow cytometry to distinguish infected erythrocytes with viable parasites from uninfected erythrocytes and erythrocytes containing dead parasites. Comparison of the fluorochromasia technique of enumerating the number and viability of hemoparasites in cultured erythrocytes with enumeration in Giemsa-stained films and uptake of [3H]hypoxanthine demonstrated the fluorochromasia technique yields comparable results. Studies with the hemoparasite, Babesia bovis, have shown the fluorochromasia technique can also be used to monitor the effect of parasiticidal drugs on parasites in vitro. The cumulative studies with the fluorochromasia assay suggest the assay will also prove useful in investigations focused on analysis of the immune response to hemoparasites and growth in vitro.

Animals↗
PubMed1991

Negative signaling by surface IgM on B cells isolated from ileal Peyer's patch follicles of sheep.

Lymphoid follicles from the sheep ileal Peyer's patch (PP) were used to prepare a cell suspension consisting of 98% surface IgM-positive (sIgM+) B cells and 1% T cells. Co-stimulation of follicular cells with pokeweed mitogen and either recombinant bovine interleukin 1 (IL 1) or IL 2 resulted in a marked proliferative response. In contrast, the addition of soluble F(ab')2 rabbit anti-sheep Ig completely inhibited the proliferative response induced by pokeweed mitogen and IL 1 or IL 2 co-stimulation. Anti-Ig inhibition of B cell proliferation was specific for ileal PP follicular cells and was not observed with mesenteric lymph node cells or splenocytes. Furthermore, suppression of ileal PP follicular B cell proliferation required at most divalent cross-linking of sIg was independent of Fc receptors, but was dependent on the concentration of anti-Ig and required 48 h for maximal effect. Negative signaling by sIgM indicates that ileal PP follicular B cells are functionally distinct from B cells in other secondary lymphoid tissues. Also, the present observations are consistent with previous reports indicating that B cell proliferation in ileal PP follicles is antigen independent.

Animals↗
PubMed1991

Analysis of bovine herpesvirus 4 (DN 599) major antigens with monoclonal antibodies and polyclonal immune serum.

Monoclonal antibodies (MAbs) and polyclonal immune sera were produced and used to identify the major antigens of bovine herpesvirus type 4 (BHV-4). SDS-polyacrylamide gel electrophoresis of immunoprecipitates of radiolabeled lysates from infected cells resolved 24 peptide bands varying from 12 kDa to over 300 kDa. Six peptides were identified as major viral antigens by immunoprecipitation. Based on the pattern of radioimmunoprecipitation, MAbs were assigned into four groups. Group 1 precipitated a tunicamycin-sensitive glycoprotein complex which contained six components (245, 190, 152, 123, and 48/46 kDa). Deglycosylation with endoglycosidase F revealed two peptides with Mr of 93 and 38 kDa as the basic peptides of the glycoprotein complex. In addition, a 115 kDa glycopeptide containing glycan-peptide bonds of mixed type was identified. Group 2 precipitated a non-glycosylated protein complex consisting of three monomers (33/31/30 kDa). Groups 3 and 4 reacted with single monomeric non-glycosylated peptides with Mr of 48 and 14 kDa, respectively. Although none of the MAbs exhibited significant neutralizing activity, some reacted strongly in immunosorbent and/or immunohistochemical assays, suggesting they may be good candidates for use in diagnostic assays.

Animals↗
PubMed1991

Individual antigens of cattle. Bovine CD2 (BoCD2).

The data obtained in the workshop provide further evidence that CH128A and IL-A26 and the 12 new mAbs that form a cluster recognise the bovine orthologue of CD2. The mAbs inhibit rosetting with SRBC, stain cells in primary and secondary lymphoid organs in patterns consistent with those obtained in humans with anti-CD2 mAbs, and the 11 IgG mAbs all immunoprecipitate a peptide with a Mr of 58-62 kDa. It is not clear from the studies whether the epitopes defined by the mAbs correspond with the region I and II epitopes present on CD2. None of the data suggest that any of the mAbs recognise the region III (CDD2R) epitope (Peterson and Seed, 1987; Knapp et al., 1989). Further studies are now needed to define the physical and functional relation of the epitopes and establish whether antibody-mediated activation corresponds with that noted in humans. Data reported in one study (Baldwin et al., 1988) with IL-A26 suggest possible differences in the requirements for activation. In addition, further studies are needed to demonstrate how many cell types express BoCD2. In mice, evidence has been presented which shows the mouse orthologue is expressed on some B cells (Yagitta et al., 1989). Studies in cattle have clearly shown CD2 is present on the majority of CD4+ and CD8+ T-cells and a small population of CD4-/CD8- cells (Baldwin et al., 1988; Davis, unpublished observations). Evidence presented in this workshop has shown that some CD2+ cells express a WC2 molecule (Sopp et al., 1991).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Individual antigens of cattle. Differentiation antigens expressed predominantly on CD4- CD8- T lymphocytes (WC1, WC2).

The 14 mAbs representing workshop cluster 1 recognise a 215/300 kDa antigen expressed on a subpopulation of lymphocytes which express low levels of CD5 but are negative for other B and T cell markers defined by workshop antibodies. Separate studies with cDNA probes for bovine CD3 and T cell receptor indicate that these lymphocytes are gamma/delta T cells. It is of note that the different mAbs react with varying proportions of this cell population, suggesting that the antigen undergoes considerable post-translational modification. A further two mAbs, designated workshop cluster 2, react with a 37/47 kDa heterodimeric molecule expressed in a subpopulation of the WC1+ cells and on an additional small population of T lymphocytes. The cell populations recognised by the two mAbs are different although they overlap in some animals. It is suggested that these mAbs may be specific for T cell receptor molecules.

Animals↗