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Biomedical subjects

O Vainio

Publications and source records attributed to O Vainio.

At least 127 records · Page 7Linked to original sources
PubMed1984

Proliferation of chicken peripheral blood leukocytes in response to pokeweed mitogen is macrophage dependent.

Chicken peripheral blood leukocytes (PBL) proliferate in vitro in response to a wide range of pokeweed mitogen (PWM) concentrations. The PWM response was not influenced by the major histocompatibility complex (MHC) haplotype nor by the intrinsic responsiveness of the PBL to concanavalin A (Con A). The results indicate that PWM under our conditions stimulates B-lineage cells, although a T-cell subset is also clearly induced to division. The PBL from B-cell-depleted animals gave substantially lower responses than those from normal controls. Pokeweed mitogen stimulation of PBL was adherent cell dependent. Thus the low PWM response of adherent cell-depleted PBL was reconstituted by the addition of irradiated unseparated PBL. Furthermore, purified irradiated adherent cells containing greater than 90% macrophages were also able to reconstitute PWM responses. Finally, we have shown that PWM was able to induce large numbers of B cells to produce cytoplasmic immunoglobulin. However, only a minor proportion of such cells were induced to immunoglobulin secretion.

Animals↗
PubMed1984

B-L antigens (class II) of the chicken major histocompatibility complex control T-B cell interaction.

The detailed study of the genetic control of T-B cell interactions in the chicken has been hampered by the lack of defined major histocompatibility complex (MHC) recombinant chicken lines. In the present study we have used some recently described MHC recombinant chicken lines separating regions encoding antigens that are homologous to class I and class II antigens of mammals in adoptive bursa cell transfer experiments, in which bursa cells from newly hatched chicks were transplanted into cyclophosphamide (Cy)-treated chicks. Subsequent immunizations of the recipients with a thymus-dependent antigen (SRBC) and a thymus-independent antigen (Brucella abortus) showed that the generation of germinal centers in the spleen and the production of antibodies to SRBC required identity between donor and recipient class II antigens (B-L antigens), whereas response to Brucella antigen did not require identity at any of the known MHC loci of the chicken. The results thus reveal that also in the chicken class II (B-L) region genes encode cell-surface glycoproteins that serve as restriction elements in T-B cell cooperation.

Animals↗
PubMed1983

Genetic control of the response of chicken T lymphocytes to concanavalin A: cellular localization of the low responder defect.

Genetic variation in the response of chicken lymphocytes to the T cell mitogen concanavalin A (Con A) has previously been studied by assaying tritiated thymidine [( 3H]dThd) uptake of cultured cells following mitogen stimulation. Our present results show, firstly, that low [3H]dThd uptake (e.g. in cultures of Con A-stimulated cells from low responder CB, CC or G-B1-lo birds) is correlated with low proliferative activity and with reduced capacity to form Con A-dependent T cell colonies in semi-solid agar. Secondly, in cultures containing mixtures of cells from high and low responder birds, the cells from each partner respond independently to Con A (there is neither suppression of high responder, nor activation of low responder cell proliferation). Finally, Con A-stimulated cultures of high responder cells respond better to T cell growth factors, as well as producing more growth factor activity, than cultures of low responder cells. These results suggest that the basis for the low responder phenotype is an intrinsic inability of low responder T lymphocytes to respond to Con A by differentiating into growth factor-sensitive blast cells.

Animals↗
PubMed1983

Origin of peripheral blood macrophages in bursa-cell-reconstituted chickens. Further evidence of MHC-restricted interactions between T and B lymphocytes.

MHC class-I antigens on peripheral blood macrophages and bursa cells were analysed after adoptive bursa cell transfer to cyclophosphamide-treated immunodeficient chickens. We studied the expression of B-F locus-encoded antigens (B-F is homologous to mouse H-2K, D) on macrophages and B cells and found that macrophage B-F antigens are of host origin, whereas bursa cells express only donor-type B-F antigens. Both syngeneic and allogeneic bursa cells restored IgM antibody production to a T-cell-independent antigen, Brucella, but only syngeneic bursa cells could restore the IgG antibody response to a thymus-dependent antigen, sheep erythrocytes. The results indicate that B-cell maturation and macrophage-B-cell interaction are not MHC-restricted but that a restriction exists in T-cell-B-cell collaboration.

Animals↗
PubMed1983

B cell genotype determines interaction preference with T cells: no effect of maturation environment.

B cell development in the bursa of Fabricius of the chicken was examined. We constructed neonatal bursa cell chimeras (F1 leads to parent, parent leads to F1) and studied the in vivo interaction of these chimeric B cells with host-derived T cells in adoptive cell transfer to determine whether there exists any environmental effect on B cells for MHC-restricted T-B cell interaction. The results indicate that F1 B cells that have developed in a parental host bursa still behave as normal F1 B cells and do not show any change in their MHC-restriction pattern. In addition, parent leads to F1 chimeric B cells were indistinguishable from normal parental B cells. B cells from all constructed chimeras, including fully allogeneic, responded well to the T-independent antigen Brucella. We conclude that the genotype of the B cell, and not the developmental environment, determines the MHC restriction phenotype of mature B cells.

Animals↗
PubMed1983

Increased endogenous retroviral gene expression is a consequence of lymphocyte activation.

Plasma cells of line 151(5) chickens have been shown to express elevated levels of endogenous retroviral envelope glycoprotein (VEG), measured relative to levels expressed by both immature B cells and resting peripheral B lymphocytes. In this study we analyzed the relationship between peripheral blood lymphocyte (PBL) maturation and the level of VEG expression. A culture system was developed that would support maturation of pokeweed mitogen-activated peripheral B lymphocytes. As analyzed by cytofluorometry, both Ig+ and Ig- lymphoblasts present in the pokeweed mitogen-stimulated cultures expressed detectable levels of VEG in contrast to bursacytes and PBL. Similarly, Ig- blasts, which were present in concanavalin A-stimulated cultures of PBL and presumed to represent activated T cells, were also positive for the expression of VEG. Immature T cells, i.e., thymocytes, although negative by immunofluorescence analysis, expressed VEG at levels that were detectable by radioimmunochemical techniques. These results indicate that T cells as well as B cells constitutively express VEG, and that mitogenic activation of the resting lymphocyte induces an increase in VEG expression.

Animals↗
PubMed1982

Studies on the chicken lymphocyte receptor for aggregated IgG.

Chicken lymphocytes isolated from different lymphoid organs were analyzed for Fc IgG receptor by binding of heat aggregated IgG (agg IgG) in the indirect immunofluorescence test. The binding of agg IgG was shown to be specific for Fc IgG receptor, since IgM and F(ab')2 fractions were bound to the lymphocytes in a much less degree. The highest frequency of agg IgG binding cells, almost 100%, was found in the bursa of Fabricius. In contrast to bursa, only a small percentage of thymus cells bound agg IgG. Dose-dependent experiments showed that binding of agg IgG to thymus cells takes place only at high concentrations of the aggregates whereas bursa cells bind agg IgG also at low concentrations. The finding indicates the existence of high and low avidity agg IgG receptors and/or different density of Fc receptors on bursa and thymus cells. A far lower percentage of EA rosette forming cells than of agg IgG binding cells in the various lymphoid organs may depend on the existence of two different Fc IgG receptors on the chicken lymphocytes.

Animals↗
PubMed1981

A rosette assay for identification of Ia-like alloantigens on chicken lymphoid cells.

An Ia-rosette assay for the detection of Ia-like alloantigens on the chicken lymphoid cell surface is described. The method is based on the ability of cells treated with alloantiserum to Ia and then with rabbit antiserum against the Fc portion of chicken IgG, to form rosettes with sheep erythrocytes (SRBC) coated with chicken anti-SRBC IgG antibody. Interference with Ia-rosette formation by Fc IgG receptors was eliminated by pronase treatment which removes Fc receptor activity without affecting Ia antigens. The Ia-rosette assay is at least as sensitive as the triple-layer immunofluorescence test for identification of Ia antigens. In addition, the assay allows morphological study and separation of the rosetting cells.

Animals↗
PubMed1981

Enhancing effect of surgical bursectomy on antibody response.

Effect of surgical bursectomy on antibody response was studied in chicks injected intrabursally with sheep red blood cells (SRBC) and Brucella abortus on day 2 of life and challenged intravenously with the same antigens on day 9. Bursectomy performed 2 days after the priming resulted in a significantly decreased anti-SRBC plaque-forming cell (PFC) response, whereas bursectomy performed 4 or 5 days after the priming clearly enhanced the PFC response. The enhancing effect of bursectomy on the PFC response was also observed if the priming was made intravenously. In antibody titers against SRBC the enhancing effect was observed only if a secondary and tertiary challenge was performed at the age of 28 and 36 days, respectively. Titers of Brucella antibodies were either reduced by the bursectomy (performed 2 or 4 days after the intrabursal priming) or left unaffected (bursectomy performed 5 days after the priming). These findings are discussed in relation to bursa-derived suppressor cells.

Animals↗
PubMed1981

T cell dependent B cell differentiation in the chicken.

Transplantation of bursa cells into surgically thymectomized (STx), cyclophosphamide(CY)-treated and X-irradiated (X) newly hatched chicks resulted in a morphological and functional reconstitution of the bursa-dependent immune system only when the transplanted bursa cells were supplemented with thymus cells. Without supplementation with thymus cells, morphological restoration of the bursa, antibody formation to sheep red blood cells and Brucella abortus, and germinal center formation remained deeply deficient. Bursa cells alone induced a full reconstitution of the bursa-dependent immunity in non-thymectomized. CY-treated and X-irradiated cell recipients. The incomplete restoration of STx-CY-X chickens after transplantation of bursa cells was not due only to lack of T helper cells, as indicated by the incomplete restoration of the bursal morphology and of antibody formation against Brucella abortus, a thymus-independent antigen. It is concluded that T cells are necessary for the B cell differentiation in the bursa of Fabricius. The mechanism behind this phenomenon remains unclear but our results indicate that a complete T cell function is not a prerequisite for this, since STx-CY-X birds reconstituted with bursa and thymus cells together did not have their mitogen (PHA, Con A) responses normalized.

Animals↗
PubMed1980

A simple method for detecting cells producing antibodies of specific immunoglobulin classes in the chicken.

A simple plaque method for detecting cells producing antibodies of specific immunoglobulin class in the chicken is described. This method is based upon the inability of chicken antibody to activate guinea-pig complement. IgM- and IgG-specific plaque-forming cells in the spleen of chickens immunized with sheep red blood cells were detected using guinea-pig complement and rabbit anti-chicken-mu- or gamma-chain serum. The specificity of the immunoglobulin class of plaques was confirmed by the abolition of class-specific hemolytic plaques after treatment of the lymphoid cells with rabbit antisera specific for chicken heavy chains in the presence of guinea-pig complement. The method is very simple and rapid, and IgM and IgG specific plaques are reliably detected.

Animals↗
PubMed1979

Germinal center formation in BSA-tolerant chickens.

In chickens rendered neonatally tolerant to BSA the germinal center formation was significantly decreased after stimulation with BSA at the age of 3 weeks. At the breakdown of tolerance after the age of 6 weeks the IgG antibody formations recovered before the IgM production. Stimulation of tolerant birds with unrelated antigens resulted in slightly decreased antibody response but the germinal center formation was on the same level as in normal controls.

Aging↗
PubMed1979

Maturation of bursal stem cells within allogeneic or syngeneic bursal microenvironment: surface determinants and capacity for germinal centre formation.

Maturation of bursal stem cells in an allogeneic environment was studied. The occurrence of surface IgM, surface IgG, and Ia-like antigens on B cells after differentiatoin within an allogeneic bursa was studied. Furthermore, the immediate capacity of B cells to form germinal centres after differentiation in an allogeneic bursa was studied by injecting them with histocompatible T cells into "test-tube" birds. The results indicate that the switch to surface-IgG-bearing cells occurs in an allogeneic bursa in a similar manner as in a syngeneic bursa. Studies of the occurrence of Ia-like antigens on bursa cells demonstrate that they retain their original Ia-like antigens, even during maturation in an allogeneic host. Third, the results demonstrate that after differentiation within an allogeneic environment bursa cells have acquired the ijmediate capacity to cooperate with histocompatible T cells as measured by germinal centre formation in "test-tube" birds.

Animals↗