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T Umiel

Publications and source records attributed to T Umiel.

17 recordsLinked to original sources
PubMed1979

Characterization of reactive and suppressive cells in the mouse embryonic liver by peanut agglutinin (PNA).

Embryonic liver cells suppressed the MLC response of adult mouse spleen cells and reactivity to mitogens Con A, PHA and LPS. Suppression was exerted by cells agglutinated by PNA (PNA+ cells). Cells reacting to LPS and to DxS were found in the nonagglutinated (PNA-) cell fraction. The PNA+ fraction did not react to DxS nor did it reduce the response of sdult spleen cells to this mitogen.

Animals↗
PubMed1978

Ontogeny of suppressor cells. II. Suppression of graft-versus-host and mixed leukocyte culture responses by embryonic cells.

Ontogenic development of suppressor cells was studied in mouse embryos. It was found that liver cells of embryos at various stages of gestation were capable of interfering with the mixed leukocyte culture (MLC) reaction. The MLC reaction was also inhibited by embryonic spleen and thymus cells. However, the latter were inhibitory only when originating in 16- and 17-day-old embryos. Embryonic liver cells were also found to interfere with the graft-versus-host (GVH) response induced in neonatal (BALB/c x C57BL)F1 or (C3H X C57BL)F1 mice by adult parental-type C57BL spleen cells. The effect was expressed in the mortality rates but was less pronounced in the splenomegaly reaction measured in vivo or in an in vitro test system. Suppression of the GVH mortality response was manifested predominantly when the liver cells were syngeneic with the effector cells. In contrast, the MLC reaction was inhibited by liver cells syngeneic or allogeneic with the effector cells. The possible developmental patterns of these cells are discussed.

Animals↗
PubMed1978

Syngeneic GvH induced in popliteal lymph nodes by spleen cells of old C57BL/6 mice.

The frequency of autoimmune processes seems to increase with age. We have studied here whether lymphoid cells of aged mice have the potential to express autoreactivity by the use of the in vivo graft-vs-host (GvH) assay. It was found that spleen cells from old (104 weeks) C57BL mice caused significant enlargement of the popliteal lymph node upon injection into the footpads of syngeneic young or old recipients. Histologically this enlargement presented characteristics of a GvH reaction. This effect, which was not abolished by irradiation of the hosts, was totally cancelled by in vitro irradiation or by anti-theta treatment of the donor cells. These results indicate that T cells from aged mice have the potential to manifest autoimmune reactivity.

Aging↗
PubMed1976

Immunosuppression by fetal liver as a model for tolerance to self.

The embryonic liver chimera system was used as a model to study the development of tolerance to self antigens. It was found that the permanent tolerant state which was induced in (C3H/eb x C57BL/6)F1 irradiated hosts following reconstitution with parental C57BL liver cells could be due to the development of suppressor cells within the liver cell inoculum, which specifically prevent reactivity of immunocompetent cells. General suppressor activity could be found in embryonic liver cells at early stages of gestation. However, the differentiation of such cells into specific suppressor of "self" antigens is dependent on the presence of the thymus.

Animals↗
PubMed1976

Augmentation of cell mediated lysis (CML) by THF.

The in-vitro model of cell mediated lysis (CML) was used to study whether a thymic hormone (THF) participates in the processes which lead to generation of effector cells. It was found that THF increases the capacity of effector cells from spleens of intact mice in the CML assay. This effect of THF on generation of effector cells was manifested when THF was present during the mixed lymphocyte culture. On the other hand, addition of THF to the effector (CML) phase did not elevate the lytic capacity of killer cells. Moreover, THF compensated the impaired lytic capacity of effector cells from adult thymectomized mice and raised it to the level of intact mice. The results are compatible with the hypothesis that THF acts on the generation of CML effector cells of both intact and adult thymectomized mice.

Animals↗
PubMed1975

Recent studies on the role of the thymus in early stages of lymphopoiesis and immune differentiation.

The influence of thymus deprivation and thymus restoration was studied: a) on the cycling capacity of colony forming cells (CFU-S) in the bone marrow and b) on the establishment of tolerance in liver radiation chimeras. After neonatal thymectomy a reduction in the number of CFU-S in the bone marrow was observed. This reduction was accompanied by a striking decrease in the proportion of cycling cells in the bone marrow of thymus deprived mice. On the other hand, restoration of thymus function by thymic hormone (THF), by implantation of thymus in semi-impermeable cellophane bags, or by pregnancy, raised the number of cycling cells in the bone marrow to that of normal controls. Parental embryonic liver cells reconstitute lethally irradiated mice, and permit establishment of tolerance to further challenges of immunocompetent cells syngeneic to liver donors. We found here that adult thymectomy prevents the establishment of permanent tolerance in liver chimeras. Again, restoration of thymic function by THF permitted liver chimeric mice to resist the immunologic attack of parental spleen lymphocytes syngeneic to donor liver cells.

Age Factors↗
PubMed1975

Increased reactivity of responding cells in the mixed lymphocyte reaction by a thymic humoral factor.

A thymic humoral factor (THF) induces competence in a certain sector of the lymphoid cell population. The target cell for THF activity was studied using the one-way mixed lymphocyte culture (MLC). Cells from various lymphoid tissues (responding cells) were preincubated in THF for 1 hour and then mixed with mitomycin-C-treated cells (stimulating cells). The results obtained indicate that THF increases MLC competence of lymphocytes from spleen and thymus origin of intact mice and that of spleen of thymus-deprived mice. In contrast, no enhancing effect in the MLC response by THF could be observed when bone marrow-derived spleen cells, cortisone-resistant thymocytes or lymph node cells were used as responding cells. These results confirm our hypothesis that THF leads to differentiation of young thymus-derived (T) cells, promoting them to maturation and thus to the acquisition of full immune competence.

Animals↗
PubMed1975

Specific inhibition of the graft-versus-host reaction in fetal or neonatal liver chimeras.

The fetal liver chimera system was used as a model to study the nature of transplantation tolerance in radiation chimeras. A permanent state of tolerance was induced in (C3H/eb times C57BL/6)F1 irradiated mice after reconstitution with parental C57BL/6 fetal or neonatal liver cells. It was found that although enough host hemopoietic cells were present in such chimeras to provide antigenic stimulation, subsequent inoculation of these chimeras with C57BL/6 immunocompetent cells syngeneic to liver donor cells specifically abolished their response against the host. In addition, cells obtained from liver chimeras after their challenge with C57BL cells were unable to produce a graft-versus-host response upon transfer to (C3H/eb times C57BL/6)F1 newborn mice. Transfer of serum of these mice could not prevent immune reactivity of syngeneic C57BL/6 cells neither in the graft-versus-host nor in the mixed lymphocyte culture assays. These observations are compatible with the hypothesis that suppressor cells may differentiate within the fetal liver, which specifically inhibits the immune reactivity of syngeneic cells, and thus leads to the establishment of tolerance.

Animals↗
PubMed1975

Immunosuppression by embryonic liver cells.

Liver cells from embryonic and newborn mice were found to interfere with mixed lymphocyte culture (MLC) reactions measuring either cytotoxicity by 51Cr release from target cells or 3H-thymidine incorporation. In both experimental systems a suppression was noted when the stimulator cells were syngeneic or unrelated to the liver donor. In addition, 18-day embryonic and neonatal liver cells were found to interfere with production of antibodies to alpha-dinitrophenyl-poly-L-lysine (alpha-DNP-PLL) in vitro. These findings conform with the hypothesis that embryonic cells can actively suppress immune reactions and thereby prevent a possible response to self.

Aging↗