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D Zharhary

Publications and source records attributed to D Zharhary.

11 recordsLinked to original sources
PubMed1990

Quantitative analysis of bone marrow thymic progenitors in young and aged mice.

Our studies on the capacity of bone marrow (BM) to generate T lymphocytes in aging have revealed that under the competitive conditions of thymic reconstitution, cells of aged mice are significantly inferior to those of the young. The present study was designed to further investigate the basis of this age-related change. Two mechanisms were considered: (a) The potential of BM-derived T cell precursors from aged mice to proliferate and differentiate in the thymic microenvironment is impaired. (b) The frequency of T cell precursors is reduced in BM of aged mice, thus affecting their ability to compete efficiently in reconstituting the thymus. These possibilities were studied in vitro by colonizing thymocyte-depleted fetal thymic lobes with BM cells from aged (24-month) and young (3-month) C57BL/6 mice. By determining the cell cycle duration of BM-derived cells which have seeded the thymic lobes, we found that cells originating from aged mice proliferate in the thymus at the same rate as those from young mice. Reconstitution with limiting numbers of BM cells indicated that the frequency of thymic progenitors in the BM is significantly reduced in aged as compared to young mice. We thus conclude that aging is associated with a quantitative reduction in the frequency of thymic progenitors in the BM.

Aging↗
PubMed1989

Altered VH gene segment utilization in the response to phosphorylcholine by aged mice.

Newly generated bone marrow B cell precursors of aged BALB/c mice, stimulated in splenic fragment cultures, display a markedly increased frequency of phosphorylcholine (PC)-responsive cells. This increased frequency is found for both precursors that utilize VHS107, a phenotype common to essentially all PC-specific B cells of young mice, and, surprisingly, for precursors that utilize VH genes other than VHS107. PC-specific hybridomas derived from bone marrow cells of aged mice utilize members of at least three VH gene segment families that have never been observed in PC responses of young mice. The ability of aged but not young mice to generate these unique PC-specific clonotypes may be evidence for constraints on V region utilization during repertoire development in young adults and has important implications for aging-associated changes in immune responsiveness.

Aging↗
PubMed1989

The role of IL-4 in the generation of B lymphocytes in the bone marrow.

It has been indicated that IL-4 supports the maturation of pre-B cells to B lymphocytes. The present study was designed to investigate the mechanism by which IL-4 influences this maturational process. In order to determine whether IL-4 acts directly on pre-B cells, we sorted out B220+, sIg- cells from bone marrow of young adult (C3H X C57BL/6)F1 mice. These purified populations of pre-B cells (greater than 95%) were incubated with and without 4 to 200 U/ml of rIL-4, and the generation of new B lymphocytes in these cultures was followed for several days. We found that the frequency of newly generated B lymphocytes (%sIg+) was similar in control and in IL-4-containing cultures. However, the total number of B lymphocytes was significantly higher in IL-4-containing cultures. This high number of B lymphocytes was a result of an increased survival of cells in IL-4-containing cultures. The effect was IL-4 specific because anti-IL-4 antibodies completely prevented this phenomenon. We thus conclude that IL-4 does not induce the maturation of pre-B cells but may be important in the process of B lymphocytes generation by providing a signal for survival of these cells.

Animals↗
PubMed1988

Age-related changes in the capability of the bone marrow to generate B cells.

The capability of the bone marrow (BM) to generate new B cells in aging was studied in vitro. BM cells from old (26 to 30 mo) or young (3 mo) BALB/c and (C3H/eB x C57BL/6)F1 mice were depleted of mature B cells and these surface Ig (sIg) BM cells were incubated in culture for 3 days. The frequency of newly generated B cells in these cultures was determined by assessing the frequency of slg+ cells and of B cells forming colonies in agar and by assaying the proliferative capacity of these newly generated B cells after stimulation by LPS. We found that BM cells from aged mice are significantly inferior to young ones in their capability to generate new B cells in culture. By mixing old and young slg- BM cells, we found that, in general, this reduction was not caused by a suppressive effect of T cells or of any other cells, but rather to lack of some sort of supportive cell or factor in the aged BM. In addition, we found that the frequency of cells expressing the B220 surface molecule, a B lineage-specific marker, is significantly reduced in aged BM. These results indicate that a quantitative decrease in B cell progenitors combined with changes in cell populations that are important in supporting B cell generation contribute to the age-related decrease in the capacity to generate B cells.

Aging↗
PubMed1988

Age-related changes in the capacity of bone marrow cells to differentiate in thymic organ cultures.

The capacity of the bone marrow to give rise to T cells in advanced age was studied in vitro by reconstituting fetal thymic lobes from 14-day C57BL/Ka (Thy-1.1) mice with bone marrow cells from old (24-month) or young (3-month) C57BL/6 (Thy-1.2) mice. The use of these congenic strains enabled distinguishing between donor and host contribution to the developing T cells. We found that bone marrow cells from aged mice maintained their capacity to reconstitute fetal thymic explants and to differentiate into various T-cell subsets as assessed by distinct T-cell-specific surface markers (Thy-1, Lyt-1, Lyt-2, and L3T4) and functions (concanavalin A-induced proliferative and cytotoxic responses). However, when mixtures of old and young bone marrow cells reconstituted fetal thymic explants, the cells of old mice were less efficient than those of young in their capacity to give rise to T cells. These results indicate that bone marrow cells from aged mice can reconstitute the thymus and differentiate into T cells; however, their reconstituting capacity is inferior to that of bone marrow cells from young mice.

Aging↗
PubMed1987

Ontogeny of T cells: development of pre-T cells from fetal liver and yolk sac in the thymus microenvironment.

The patterns of development of T cells from the very early stem cells that settle in the embryonic thymus have been studied. For this purpose, mouse embryonic thymuses (14 days) depleted of thymocytes were reconstituted with hemopoietic stem cells from fetal liver (FL) and yolk sac (YS) and T-cell development was followed in vitro in organ culture. It was found that cells derived from FL and YS of 10- to 14-day-old embryos were capable of reconstituting depleted thymic explants and exhibiting membrane markers in a pattern similar to that of thymocytes developing in intact thymic explants. Furthermore, these cells responded to concanavalin A in proliferative and cytotoxic assays as measured by limiting-dilution analysis. Thus, lymphohemopoietic stem cells emerging in the embryo prior to thymus lymphoid development are capable of differentiation in the thymus microenvironment into T cells, identified by phenotypic markers and functions that are characteristic of cells developing in the intact embryonic thymus.

Animals↗
PubMed1986

T cell involvement in the decrease of antigen-responsive B cells in aged mice.

The role of T cells in the reduced frequency of splenic B cells specific for several antigens in aged mice was studied by assessing B cell responsiveness in (a) aged nude mice and (b) irradiated young mice repopulated with splenic B cells or with Ig- bone marrow cells from young mice and T cells from aged vs. young mice. Using the fragment culture technique to assess B cells specific for 2,4-dinitrophenyl (DNP) and for (4-hydroxy-3,5-dinitrophenyl) acetyl, we found that the frequency of responsive splenic B cells in aged BALB/c nude mice was very similar to that of young nude mice. In addition, we found that in chimeric mice constructed with either bone marrow or splenic B cells from young mice and T cells from aged mice the frequency of DNP-specific splenic B cells was significantly lower than that in control chimeras constructed with T cells from young mice. These results indicate that T cells from aged mice can down regulate B cell responsiveness and that a mature, naive B cell may be its possible target. The results of both experimental approaches are consistent with a role for T cells in the regulation of responsive B cells in aging.

Aging↗
PubMed1986

The frequency and fine specificity of B cells responsive to (4-hydroxy-3-nitrophenyl)acetyl in aged mice.

The B-cell response to NP-Hy of two murine strains has been analyzed in order to evaluate the affects of aging on B-cell repertoire expression. The results indicate that for both BALB/c mice (Igha) and B10.D2 mice (Ighb) the frequency of (4-hydroxy-3-nitrophenyl)acetyl (NP)-responsive splenic B cells is approximately twofold lower, on a per B cell basis, in aged mice as compared to young adults. However, as with previous assessments of the response to DNP-Hy in aged mice, the frequency of newly generated surface immunoglobulin negative bone marrow precursor cells specific for NP in aged BALB/c mice is the same as in young mice. The decrease in frequency of responsive splenic B cells is not accompanied by a measurable decrease in repertoire diversity or changes in clonotype distribution as assessed by representation of kappa vs lambda light chain-bearing antibodies, binding of monoclonal antibodies to a panel of analogues of NP, and the proportionate representation of B10.D2 monoclonal antibodies that bear NPb idiotypic determinants. By these criteria it appears that down-regulation of B cells as they mature and emerge from the bone marrow of aged mice is pan-specific and does not disproportionately affect B cells of a predominant clonotype family. Consistent with other investigations which have demonstrated differences in secreted antibodies of immunized aged vs young mice, we have observed that 4 weeks after immunization of B10.D2 mice with NP-BSA, the frequency of newly generated secondary B cells is lower in aged than in young mice and the generation of lambda-bearing secondary precursor cells is particularly low. Thus, clonotype-specific down-regulation may play a role in shaping the B-cell repertoire subsequent to immunization of aged mice.

Aging↗
PubMed1977

Nitrophenylated derivatives of epsilon-aminocaproic acid: synthesis and physico-chemical characterization.

Methods for the synthesis of the mono-, di- and tri-nitro derivatives of epsilon-aminocaproic acid are presented. Special attention is given to the purification procedure, as we have found that methods recommended in the literature do not produce a single product. Evidence is presented which shows that recrystallizing the haptens from hot ethanol produces a by-product which is the ethyl ester of the haptens. Characterization methods and physical properties of the nitro-phenylated derivates of epsilon-aminocaproic acid are summarized.

Aminocaproates↗
PubMedDate not supplied

The affinity and spectrum of cross reactivity of antibody production in senescent mice: the IgM response.

Experiments were performed to determine whether the IgM component of the primary humoral immune response of senescent mice differs from that of young-adult mice in its affinity, specificity or heterogeneity. For this purpose, mice were immunized with the T-dependent antigen, TNP-KLH, or the T-independent antigen, TNP-LPS. Affinity and specificity of the anti-TNP response were studied at the cellular level by the plaque inhibition technique using the cross-reacting haptens TNP-epsilon-aminocaproic acid )TNP-EACA),DNP-EACA and ONP-EACA. It was found that when the immunogen was TNP-KLH, the peak IgM response was delayed in senescent animals by several days as compared to the response in young adults. However, the number of PFC on the day of peak response was comparable. No age related delay in the peak of response was detected when the antigen was TNP-LPS although the magnitude of response was reduced in old age. The average affinity of the plaque forming cell responses to both immunogens is comparable in young and old mice.

Aging↗