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Biomedical subjects

Y Bito

Publications and source records attributed to Y Bito.

At least 37 records · Page 2Linked to original sources
PubMed1980

The development of unusual B-cell functions in the testosterone-propionate-treated chicken.

Chickens were treated with 4 mg of testosterone propionate on the twelfth day of embryonic life. Bursal remnants of testosterone-treated chickens were very small in size and had very few or no bursal follicles: the lymphoid tissue was replaced substantially by fibrosis. Testosterone-treated chickens formed almost exclusively IgM antibodies to sheep red blood cells and influenza virus, whereas no IgM or IgG response to Brucella abortus or Salmonella pullorum, and no IgG response to sheep red blood cells was demonstrable. Surgical removal of bursal remnants of testosterone-treated chickens at hatching did not significantly affect IgM response to sheep red blood cells. These B-cell functions of testosterone-treated chickens were not improved by addition of T cells, as shown by adoptive cell transfer experiments. Thus, there appears to be an unusual type B-cell development which is independent of the bursa of Fabricius.

Animals↗
PubMed1980

The B-cell development independent of the bursa of Fabricius but dependent upon the thymus in chickens treated with testosterone propionate.

Spleen cells taken from chickens treated with testosterone propionate, surgically bursectomized and immunized, were treated with anti-bursa-cell antiserum in the presence of complement, and transferred together with the mixed antigens into immunodeficient chickens. The recipient chickens showed restored capacity for antibody response to sheep red blood cells. In contrast, adoptive immune responses by spleen cells from normal chickens were abolished by treating with anti-bursa-cell antiserum in the presence of complement. These findings indicate that antibody-forming cells in TP-treated chickens do not bear cell-surface antigens specific for bursa cells; Testosterone-treated chickens were thymectomized at 7 days of age and immunized with the mixed antigens; the chickens thus treated were not able to produce antibodies. Thymocytes and thymus-derived cells taken from normal chickens were transferred into the testosterone-treated and surgically thymectomized chickens; but the antibody responses were not restored, indicating that absence of antibody formation in testosterone-treated, thymectomized birds is not due to lack of T cells as such. This result was confirmed by using adoptive transfer of B cells taken from testosterone-treated chickens together with T cells.

Animals↗
PubMed1980

A T-cell subpopulation committed to help B cells for immune responses restricted to IgM type.

Immune responses againt bovine serum albumin by chicken were dependent upon thymus-derived cells. Thirty-five of seventy chickens that had been neonatally thymectomized and subsequently immunized with bovine serum albumin produced IgM antibodies, but not IgG antibodies, against the antigen. T cells (IgM-T cells) of such chickens were able to help B cells to produce IgM antibody responses but were not able to help them to switch IgM- to IgG-antibody responses. Helper activity of the IgM-T cells was much less susceptible to the cytotoxic effect of anti-thymus cell serum and complement than was that of normal T cells. The introduction of the IgM-T cells into normal chickens at the same time as the initiation of immunization of the chickens did not affect immune responses by them at all, indicating the absence of suppressor T cells in the IgM-T cell preparations. Injection of chicken thymus factor into immunodeficient chickens transplanted with normal B cells and IgM-T cells developed the capability to help B cells to switch IgM- to IgG-antibody responses. On the basis of these findings the authors propose the existence of helper T cells which are characterized by peripheralization in early periods of ontogeny, the possession of helper activity for only IgM-antibody responses, the lack of helper activity for the switch from IgM- to IgG-antibody responses and relative insusceptibility to the cytotoxic effect of anti-thymus cell serum and complement.

Animals↗
PubMed1980

A B-cell subpopulation relatively insusceptible to the cytotoxic effect of anti-bursa cell serum and partially defective in immune function.

Chicken B cells treated with diluted anti-bursa cell serum in the presence of complement were transferred together with normal T cells and sheep red blood cells into immunodeficient recipient chickens, and spleen cells taken from these were examined for the development of plaque-forming cells. The production of IgM-plaque-forming cells was considerably more resistant to the cytotoxic effect of the antiserum than that of IgG-plaque-forming cells. Cells producing IgM antibodies were also less susceptible to the cytotoxic effect of the antiserum and complement than were those producing IgG antibodies. Such differential susceptibility of development of IgM- and IgG- plaque-forming cells was observed only in chickens aged about 2 weeks or younger. These findings indicate the existence of a B-cell subpopulation which is relatively insusceptible to the cytotoxic effect of the antiserum and is incapable of switching from IgM- to IgG-immune responses. The B cells resistant to the cytotoxic effect of diluted anti-bursa cell serum and complement were more susceptible to X-irradiation than were normal B cells. Immune responses against sheep red blood cells by the B cells resistant to the cytotoxic effect were dependent upon the help of T cells.

Animals↗
PubMed1978

Relationship between bactericidal action of complement and fluidity of cellular membranes.

The mode of complement-mediated killing of Escherichia coli B cells grown at 25 and 42 degrees C and of E. coli K-12 UFAts cells grown in the presence of oleic and elaidic aicds was examined in relation to their membrane lipid compositions and the thermodynamic properties of membrane phospholipids. Phospholipids isolated from 25 degrees C-grown cells of strain B and from oleic acid-incorporated cells of strain K-12 UFAts had lower phase transition temperatures than did phospholipids from E. coli strain B grown at 42 degrees C or those from strain K-12 UFAts grown on elaidic acid. The rate of cellular susceptibility to complement action closely correlated with the liquid crystalline phase of phospholipids of cell membranes. These findings suggest that membrane fluidity is obligatory for the final expression of complement action.

Blood Bactericidal Activity↗
PubMed1978

The role of the thymus for maturation of transferred bursa cells into immunocompetent B cells in chickens treated with cyclophosphamide.

Chickens injected with cyclophosphamide and X-ray irradiated in the newly hatched period were immunized with a mixture of sheep red blood cells, Brucella abortus and Salmonella pullorum at 4, 5 and 6 weeks of age, and were examined for serum antibody titres, serum immunoglobulin concentration and bursal and splenic structures at 7 weeks of age. The neonatal treatments suppressed completely or almost completely antibody responses, immunoglobulin production and formation of bursal follicles and splenic germinal centres. The transplantation of bursa cells into the chickens immunologically impaired by the treatments restored these functions and structures. In contrast, the transfer of bursa cells into chickens thymectomized, cyclophosphamide-treated and X-ray irradiated did not result in efficient restoration of the bursa-dependent immune system; 10-day-old bursa cells hardly restore the system, although 4-week-old bursa cells did so slightly. The chickens thymectomized, cyclophosphamide-treated, X-ray irradiated and repopulated with 10-day-old bursa cells were examined for the existence of functional B cells with the use of a syngeneic cell transfer system. The experiments verified that immunocompetent B cells had not developed in the chickens thus treated.

Animals↗
PubMed1976

Humoral immune responses characteristic of testosterone-propionate-treated chickens.

White Leghorn chickens treated with testosterone-propionate on the 3rd day of embryonation were immunized with a mixture of sheep red blood cells, Brucella abortus and Salmonella pullorum at various ages, and the resulting agglutinins were titrated. The production of IgM antibody against sheep red blood cells was not affected significantly by testosterone-propionate. On the contrary, immune responses against the bacterial antigens were strongly suppressed by the same treatment. Production of IgG antibodies was strongly suppressed by the same treatment. There was little correlation between the production of IgM antibody against sheep red blood cells and the presence of bursal follicles. Immune responses against bacterial antigens correlated with the presence of the follicles. Production of IgG antibodies also correlated with the maintenance of bursal lymphoid structure.

Agglutinins↗
PubMed1976

The augmentation of antibody responses by preliminary intrabursal priming in the chicken.

Direct injection of antigen into bursal tissue of young chickens followed by subsequent intravenous immunization markedly stimulated agglutinin production against Brucella abortus. In contrast, preliminary intravenous immunization did not produce stimulation. The promoting effect of intrabursal injection was antigen-specific. Antigen injection into the bursa reduced the extent to which subsequent bursectomy suppresses the immune response. Bursa cells from young chickens which had been injected with antigen intrabursally were active in transferring the ability to give a secondary response to B. abortus when injected into bursectomized-irradiated chickens. The cells derived from chickens primed intravenously or from normal chickens were inactive. The implant of bursa cells from the 18-day-old chickens which had been injected with antigen intrabursally or intravenously at 11 days of age showed a promoting effect in restoring the ability to give secondary responses to both of B. abortus and Salmonella pullorum as compared with that of the implant of the bursa cells from unimmunized donors. These findings are discussed in relation to the existence of precursor cells that can respond to the antigen with a potential to enhance the antibody response to subsequent antigenic stimuli but are not yet mature enough to produce the antibody.

Age Factors↗
PubMed1975

Diverse effects of bursectomy on humoral immune responses in the chicken.

Chickens bursectomized hormonally or surgically at various ages in embryonic to postembryonic lives were immunized with a mixture of antigens, and the antibodies produced titrated. immune responses to Salmonella pullorum (SP), Brucella abortus (BA). Staphylococcus aureus (Staph) and ovalbumin (OA) were more markedly suppressed by the bursal deprivation than those to heterogenous erythrocytes, viruses and such bacteria as Pasteurella multocida (PM) and Escherichia coli B. The immune response to bovine serum albumin (BSA) was on a level between the two groups. Hormonal bursectomy in embryonic life permitted chickens immunized with sheep red blood cells (SRBC) to produce antibody of the IgM type but not of the IgG type. In surgically bursectomized chickens IgG but not IgM production was inhibited. Chickens hormonally bursectomized on the third day of egg incubation produced IgM to a level higher than the normal chickens in contrast with the suppressed IgG production. Such diversity in the bursal influences on antibody responses was discussed in relation to ontogeny of the humoral immune system.

Animals↗
PubMed1975

The bursal origin of an immunocompetent cell for antibody formation in the chicken.

Surgically bursectomized and irradiated chickens were given bursal, splenic, bone marrow or thymic cells taken from syngeneic donors, together with killed Brucella abortus and Salmonella pullorum. Blood samples were taken from those chickens 7 days later, and the serum agglutinin titres were determined. The cells of any lymphoid organ taken from 28-day-old chickens were more effective in restoring antibody response than those from 18-day-old ones. The restorative capacities of the bursa and splenic cells were greater than those of the bone marrow and thymic cells. On the other hand, splenic, bone marrow or thymic cells taken from bursa-less chickens, and lymphoid cells taken from normal chickens but treated with anti-bursa serum in the persence of complement, were virtually incapable of restoring the immune response. Bursal, splenic or bone marrow cells taken from neonatally thymectomized chickens, and bursal or thymic cells treated with anti-thymus serum were effective, being comparable with the corresponding cells taken from normal chickens or treated with normal sera, in restoring the suppressed immune response in chickens devoid of the lymphoid system. These facts clearly indicate that the primary and central agent crucial for development of the humoral immune response against the two bacterial antigens tested is the bursa. It is strongly suggested from the results of adoptive immunization using intrabursally primed cells that the cells recognizing Brucella abortus exist within the bursa of 4-day-old chicken.

Animals↗