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Biomedical subjects

W C Davis

Publications and source records attributed to W C Davis.

At least 199 records · Page 11Linked to original sources
PubMed1989

Monoclonal antibodies to bovine major histocompatibility system antigens.

Of 89 monoclonal antibodies screened for anti-class I activity in a cytotoxic assay against bovine peripheral-blood lymphocytes, 6 reacted with all lymphocytes from all cattle tested, 72 failed to react at all and 11 reacted with polymorphic determinants. The reactivity of some of the 11 polymorphic monoclonal antibodies was dependent upon the bovine major histocompatibility system (BoLA) class I type. Eight monoclonal antibodies selected for putative anti-class II activity reacted with B-enriched lymphocytes from all cattle tested.

Animals↗
PubMed1988

T lymphocyte development in horses. I. Characterization of monoclonal antibodies identifying three stages of T lymphocyte differentiation.

Six monoclonal antibodies reacting with equine T lymphocytes at different stages of maturation were selected from antibodies produced against lymphoid cell preparations. EqT12 and EqT13 antibodies identified subsets of cortical thymocytes with high terminal deoxynucleotidyltransferase (TdT) activity and no phytolectin responsiveness. EqT12+ thymocytes were scattered throughout the cortex while EqT13+ thymocytes were located in the subcapsular cortex. EqT12 bound to small numbers of bone marrow cells, splenocytes, and circulating lymphoid cells, but not to mature T lymphocytes. EqT13 bound to very small numbers of bone marrow cells but not to more mature lymphocytes. EqT6 and EqT7 reacted with a large population of cortical thymocytes with high TdT activity and no phytolectin responsiveness. EqT2 and EqT3 bound primarily to medullary thymocytes with low TdT activity. Eq2+ thymocytes responded to phytolectin stimulation while EqT3+ thymocytes did not. EqT2 and EqT3 bound to 33% and 91% of circulating T lymphocytes, respectively. The T lymphocytes bound by both antibodies included cells capable of suppressing a mixed lymphocyte reaction. Thus, EqT12 and EqT13 identify cells with the functional characteristics of prothymocytes. EqT6 and EqT7 identify resident cortical thymocytes, and EqT2 and EqT3 identify a subpopulation of mature T lymphocytes and all mature T lymphocytes, respectively.

Animals↗
PubMed1988

Differentiation antigens on bovine mononuclear phagocytes identified by monoclonal antibodies.

Five monoclonal antibodies (MAb) produced against cell surface antigens on bovine mononuclear phagocytes (MPh) were characterized. None of the MAb recognized erythrocytes, thrombocytes, B lymphocytes or resting or activated T lymphocytes. Two MAb (IL-A22 and IL-A24) reacted with the majority of monocytes and granulocytes in peripheral blood, with 20-40% bone marrow cells comprising myelo-monocytic cells, and with a proportion of mature macrophages. Reactivity of the remaining three MAb was restricted to MPh: one of these (IL-A25) was apparently specific for pulmonary macrophages, whereas the molecules recognized by the other two (IL-A23 and CH16A) were expressed on subpopulations of blood monocytes and tissue macrophages. None of the MAb inhibited adherence of MPh to plasma-coated gelating surfaces or Fc-mediated rosette formation. One of the MAb, IL-A24, which reacts with MPh and granulocytes, inhibited antigen-specific proliferative response or peripheral blood mononuclear leukocytes (PBM) to the soluble antigen, keyhole limpet hemocyanin (KLH) but did not inhibit responses to concanavalin A or allogeneic leukocytes. This MAb was shown to react with two polypeptides of approximately 75 kD and 110 kD on the surface of peripheral blood monocytes.

Animals↗
PubMed1988

Characterization of a bovine thymic differentiation antigen analogous to CD1 in the human.

Three monoclonal antibodies (MoAb), TH97A, CC13, and CC14, define a thymic differentiation antigen in cattle. The antigen is expressed on 50-60% of bovine thymocytes, located mainly in the cortical areas, but is not expressed on peripheral blood mononuclear cells (PBMC). In cryostat sections of lymph node, the antibodies react with large dendritic-like cells in the paracortical regions. They also react with a proportion of the large 'frilly' cells in afferent lymph and with dendritic-like cells in the dermis. The antibodies apparently do not react with cells in the epidermis. Biochemical analysis of the antigen recognized by MoAb TH97A reveals two bands of 44 kDa and 12 kDa under reducing conditions. These polypeptides are distinct from bovine class I major histocompatibility complex molecules reactive with the MoAb w6/32. The tissue distribution of positive cells together with results of biochemical analyses indicate that the antigen recognized by these MoAb is the bovine analogue of the human CD1.

Animals↗
PubMed1988

Immunization of cattle with a 36-kilodalton surface protein induces protection against homologous and heterologous Anaplasma marginale challenge.

Immunization of cattle with a purified Anaplasma marginale major surface protein, AmF36, induced protection against homologous challenge with the Florida isolate. Similarly, immunized cattle were protected from challenge with the antigenically and structurally distinct Washington-O isolate of A. marginale. The degree of protection in AmF36-immunized cattle varied from complete prevention of rickettsemia to significant delay in the onset of rickettsemia compared with control immunized cattle. A single AmF36 vaccinate was not protected against homologous challenge despite development of a strong antibody response. Immunoprecipitation of A. marginale proteins with a monoclonal antibody to AmF36 identified minor molecular size heterogeneity in this protein from different isolates, including the Florida and Washington-O isolates. The apparent molecular size of this surface protein in the Florida isolate was 36 kilodaltons, whereas the analogous proteins in Washington-O and four other isolates of A. marginale from the United States had molecular masses of 33 to 34 kilodaltons. Significantly, the surface-exposed peptides of these proteins appear to be conserved among the different isolates. These results demonstrate the potential of AmF36 as a subunit immunogen for bovine anaplasmosis and indicate a structural basis for its cross-protective ability.

Anaplasma↗
PubMed1988

Identification of Babesia bovis merozoite surface antigens by using immune bovine sera and monoclonal antibodies.

Three Babesia bovis merozoite surface proteins with relative molecular weights of 37,000, 42,000, and 60,000 were identified by indirect immunofluorescence of live merozoites and by immunoprecipitation of 125I-surface-labeled merozoite proteins with immune bovine sera and monoclonal antibodies. These proteins were clearly of parasite origin, as evidenced by immunoprecipitation of metabolically labeled [( 35S]methionine) merozoites from cultures with specific antimerozoite monoclonal antibodies. In addition, two other proteins were identified with these methods. An 85-kilodalton protein was considered to be of parasite origin based on fluorescence reactivity with a monoclonal antibody. However, this protein was not detected after immunoprecipitation of metabolically labeled parasites, and thus, the exact nature of its origin is equivocal. A fifth protein of 145 kilodaltons was detected by immunoprecipitation after metabolic labeling but was not directly apparent on the surfaces of live merozoites. Since merozoite surface proteins may be important in the induction of protective immunity, those identified here are candidates for vaccine studies.

Animals↗
PubMed1988

Flow cytofluorimetric analysis of lymphocyte subset alterations in cattle infected with bovine viral diarrhea virus.

Clinically normal, bovine viral diarrhea virus (BVDV)-seronegative, 7 to 9-month-old steers were inoculated intranasally with NY-1, a noncytopathic strain of BVDV, or exposed intramuscularly to killed BVDV. Indirect immunofluorescence staining with monoclonal antibodies specific for bovine leukocyte subsets followed by flow cytometric analysis was used to monitor subsequent hematologic alterations. Infection with BVDV resulted in a transient leukopenia which was characterized by decreases in the absolute numbers of circulating T lymphocytes, including BoT4+ ("helper") and BoT8+ ("cytotoxic/suppressor") subsets, B lymphocytes, and neutrophils. There was no significant variation in numbers of non-T, non-B ("null") lymphocytes or monocytes. Exposure to inactivated BVDV in a combination vaccine did not cause significant alteration in the circulating numbers of any major leukocyte subset; however, significant variation was seen in the BoT4/BoT8 ratios and in the numbers of cells expressing major histocompatibility complex (MHC) class II antigens.

Animals↗
PubMed1988

Immunocytochemical identification of bovine Langerhans cells by use of a monoclonal antibody directed against class II MHC antigens.

We undertook a study to develop a reliable light microscopic technique for identifying Langerhans cells (LC) in bovine epidermis. Monoclonal antibodies (MCA) detecting bovine class II MHC antigens were used in conjunction with an avidin-biotin-peroxidase complex (ABC) immunocytochemical staining method. The specificity of the MCA for LC was confirmed ultrastructurally by use of gold-labeled second antibody. Epidermal sheets and epidermal single-cell suspensions examined by light microscopy confirm that bovine epidermal LC express class II antigens. Anti-bovine class II MCA is a dependable reagent for identification of LC in normal bovine epidermis.

Animals↗
PubMed1988

A cytotoxic murine monoclonal antibody that recognizes a porcine T cell subset involved in lectin-induced proliferation.

A panel of cytotoxic monoclonal antibodies (Moab) derived from mice immunized with porcine thymocytes has been developed which reacts with monomorphic determinants on porcine peripheral blood lymphocytes (PBL). These Moab recognized from 25% to 100% of PBL as tested by flow microfluorimetry One of the Moab (PT 81) that bound 39% of PBL, 30% of splenocytes and 65% of thymocytes as determined by flow microfluorimetry was selected for initial characterization. PT 81 specifically lysed 37% of Ficoll/Hypaque-prepared PBL depleted of monocytes by carbonyl iron ingestion. This antibody lysed 47% of T cells (PBL that formed dextran-enhanced, sheep erythrocyte rosettes; P less than 0.001) and 64% of a T cell subset (PBL that formed dextran-enhanced, porcine erythrocyte rosettes; P less than 0.001) when compared to cells treated with complement alone. Lysis of PBL with PT 81 plus complement caused a 100% enrichment in the number of surface immunoglobulin positive cells (P less than 0.01). The conclusion that PT 81 does not recognize B cells was further supported by double labelling experiments. Removal of PT 81 positive cells did not significantly affect the number of cells with C3b (zymosan-complement rosettes) or Fc gamma (erythrocyte-antibody rosettes) receptors. PBL that were treated with PT 81 plus complement were passed over Ficoll/Hypaque (density 1.09) to remove dead cells. The PT 81-depleted lymphocyte population displayed only 20%, 20%, 26% and 29% of the proliferative responses of control cells treated with complement alone (P less than 0.01) to several concentrations of the mitogens phytohemagglutinin, concanavalin A, soybean agglutinin and pokeweed mitogen, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Enumeration of T and B lymphocytes in bovine leukemia virus-infected cattle, using monoclonal antibodies.

Monoclonal antibodies and microfluorimetry were used to determine the absolute number of B and T lymphocytes in the blood of bovine leukemia virus (BLV)-infected cows. The blood lymphocyte populations from BLV-infected cows were significantly higher than those from BLV-negative cows. The increase in the lymphocyte population in 3 BLV-infected nonlymphocytotic cows was attributed to a significant increase in the number of T lymphocytes; in 3 BLV-infected persistently lymphocytotic cows, the increase was attributed to a significant increase in the number of B and T lymphocytes. One persistently lymphocytotic cow had a high lymphocyte count, and lymphocytes from this cow contained cells that appeared to stain with markers specific for bovine B and T lymphocytes. We concluded that infection of cattle with the B-cell lymphotropic retrovirus, BLV, not only affected B cells, but also T cells.

Animals↗
PubMed1988

Bovine pan T-cell monoclonal antibodies reactive with a molecule similar to CD2.

Monoclonal antibodies (mAb) CH128A and CH61A react with molecules of 50,000-60,000 MW. They are expressed by all T cells in cattle, comprising 44-69% of peripheral blood mononuclear leucocytes (PBM), the majority of lymphocytes in T-dependent areas of lymph node, and 75-80% of cells derived from the thymus including both cortical and medullary thymocytes. The molecule recognized by these mAbs is not expressed on B lymphocytes, monocytes/macrophages, or granulocytes. Both mAb inhibit spontaneous rosette formation by sheep erythrocytes and bovine lymphocytes. We postulate that these mAb see the bovine homologue of the human sheep red blood cell receptor CD2 and has been named BoT2.

Animals↗
PubMed1987

Antibodies define multiple proteins with epitopes exposed on the surface of live Babesia bigemina merozoites.

Babesia bigemina is one of several tick-borne hemoparasitic diseases of cattle that are inadequately controlled and cause substantial livestock production losses in tropical and subtropical climates. Recovery from acute babesiosis is associated with development of protective immunity against subsequent challenge with both homologous and heterologous parasites. Viable and infectious merozoites, the intraerythrocytic stage of B. bigemina responsible for clinical disease, were separated from contaminating host cells by density gradient centrifugation. Monoclonal antibodies developed against gradient-separated merozoites were screened for surface reactivity against live merozoites in an immunofluorescent binding assay. Surface-reactive antibodies immunoprecipitated five major biosynthetically radiolabeled merozoite proteins with relative m.w. of 72,000, 58,000, 55,000, 45,000, and 36,000 in SDS-PAGE. Two additional proteins immunoprecipitated with the 45,000 m.w. protein were unreactive with monoclonal antibody in western blots and are apparently part of a membrane complex co-precipitated by this antibody. In contrast, additional proteins of m.w. of 36,000, 35,000, and 33,000, immunoprecipitated with the 58,000 protein, all contain the surface-exposed epitope bound by monoclonal antibody. Immune serum from an animal that had recovered from infection with a Mexico isolate of B. bigemina immunoprecipitated five radiolabeled proteins from the Mexico isolate that co-migrated in SDS-PAGE with major proteins precipitated by surface-reactive monoclonal antibodies. In addition, antibodies against a Kenya isolate of B. bigemina immunoprecipitated the same co-migrating proteins from radio-labeled Mexico isolate, demonstrating epitope conservation between surface proteins of geographically different isolates. The identification of proteins with epitopes exposed on the surface of live merozoites and accessible to antibody provides candidates to be tested as protective immunogens in cattle.

Animals↗
PubMed1987

The development and analysis of species specific and cross reactive monoclonal antibodies to leukocyte differentiation antigens and antigens of the major histocompatibility complex for use in the study of the immune system in cattle and other species.

We examined the potential of developing a set of species specific and cross reactive monoclonal antibodies (MoAbs) for use in the study of the phylogenetic and functional relation of class I and class II antigens of the major histocompatibility complex (MHC) and leukocyte differentiation antigens in cattle and other species. Comparing immunization strategies demonstrated the number of hybrids producing cross reactive antibodies can be increased by hyperimmunization of mice with lymphoid cells from multiple species. Comparing various methods of assay (antibody-complement mediated cytotoxicity [CT], enzyme linked immunosorbent assay [ELISA] and flow microfluorimetry [FMF]), revealed FMF is the most useful technique for the primary assay of hybridomas producing MoAbs of potential interest. By using dual parameter and dual fluorescence analysis, we could determine whether a given MoAb reacted with mononuclear cells (lymphocytes and monocytes) and/or granulocytes, and also whether any two MoAbs of different isotype and specificity recognized antigens present on identical or separate populations of leukocytes. Comparing the patterns of MoAb reactivity with leukocytes obtained from cows, goats, sheep, pigs, horses and humans, as well as comparing the patterns of reactivity with a panel of lymphoid cell lines derived from cattle (with enzootic bovine leukemia) and humans (with various forms of leukemia), revealed sets of MoAbs reactive with unique antigenic determinants present on BoLA class I (15 MoAbs) and class II (9 MoAbs) antigens, and also MoAbs reactive with determinants present on leukocyte differentiation antigens (36 MoAbs). Dual fluorescence analysis demonstrated the antigens detected by some MoAbs are predominantly expressed on one lineage of leukocytes while others are expressed on two or more lineages of leukocytes. Dual and single fluorescence analysis also demonstrated the PNA receptor(s) is: expressed on T cells, granulocytes and class II antigen monocytes and absent or expressed in low amount on sIgM+ B cells and a newly defined Non T/Non B population of cells. The strategies described for identifying and analyzing the specificity of MoAbs demonstrate the feasibility of developing a set of cross reactive MoAbs for identifying homologous molecules in multiple species and delineating their functional and phylogenetic relation.

Animals↗
PubMed1987

Distribution of T and B lymphocytes in mammary dry secretions, colostrum and blood of adult dairy cattle.

The distribution of lymphocyte subpopulations from dry secretions, colostrum and blood from 10 healthy adult Hostein-Fresian cows was studied using the TH21A and B26A mouse monoclonal antibodies (MAb) to adult bovine B and T lymphocytes, respectively. The mammary gland lymphocytes (MGL) were isolated from composite sample of all four quarters by density centrifugation over discontinuous gradient of ficoll-diatrizoate. The peripheral blood lymphocytes (PBL) were purified using the ficoll-thrombin method. Isolated PBL and MGL were analyzed using the two fluorochromes method (TFM) and laser flow cytometry (LFC). The mean viability of isolated PBL and MGL from dry secretions and colostrum after the TFM and LFC were 92.4% +/- 3.2%, 91.4% +/- 6.0% and 87.1% +/- 6.1%, respectively. There was a good correlation between the two MAbs and the percentage of surface immunoglobulin (SIg) positive cells in the peripheral blood using the TFM. The PBL yielded a mean percentage of 21.2% B cells, 66.4% T cells and 9.4% "Null cells" (TH21A+; SIg-). The TFM on MGL from dry secretions and colostrum indicated two distinct patterns (group I and II) of SIg and reactivity to MAb markers (p less than 0.001). The MGL data included in group I and group II were gathered from both colostral and dry secretions. In comparison to the distribution of lymphocyte subsets within peripheral blood the mean percentages of B cells, T cells and "Null cells" in the mammary gland were respectively, 2.8%, 88.1% and 5.4% for group I and 3.5%, 89.0% and 15.1% for group II. In the mammary secretions, the use of SIg alone was not considered to be a good marker for B cells; in four animals a mean percentage of 15.6% (13.9/89.0 X 100) of the mammary gland T lymphocytes were also SIg+. Of the TH21A+ MGL, only 18.8% were SIg+ in group II compared with 34.1% for MGL from group I and 69.3% for the PBL. Marked differences in cell size distribution and cell surface antigen density were found when PBL and MGL from dry secretions were compared by LFC using the B26A MAb. The results of this study demonstrate a difference in the percentages of peripheral blood and mammary gland B and T lymphocytes and confirm previous findings in which the T lymphocytes were found to represent the major subpopulation of lymphocytes in bovine mammary secretions. This may represent an essential event in the adoptive transfer of cellular immunity through the colostrum in cattle.

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