Biomedical subjects

S C Clark

Publications and source records attributed to S C Clark.

At least 55 records · Page 3Linked to original sources

PubMed1994

Synergistic interaction between interleukin-12 and steel factor in support of proliferation of murine lymphohematopoietic progenitors in culture.

We have investigated the effects of interleukin (IL)-12 (natural killer cell stimulatory factor/cytotoxic lymphocyte maturation factor) on the proliferation of murine myeloid and lymphohematopoietic progenitors in methylcellulose culture. In the presence of erythropoietin (Ep), IL-12 alone failed to support colony formation by mononuclear and enriched marrow cells of normal mice. Steel factor (SF) alone supported primarily formation of granulocyte/macrophage (GM) colony formation. However, the combination of the two cytokines yielded a significant number of multilineage colonies. When tested on marrow cells from 5-fluorouracil (5-FU)-treated mice, the combination of IL-12 and SF, but not the single factors, was effective in support of formation of various types of colonies. Approximately 25% of these colonies yielded pre-B-cell colonies when replated in secondary culture containing SF and IL-7, indicating that IL-12 can interact with SF in supporting the development of primitive lymphohematopoietic progenitors. These results demonstrate that IL-12, a cytokine believed to be involved in the development of cell-mediated immune responses, has a wider range of activity, including committed myeloid and multipotent lymphohematopoietic progenitors.

Animals↗

PubMed1994

Awareness of illness in schizophrenia and schizoaffective and mood disorders.

BACKGROUND: The literature on insight, or self-awareness, in schizophrenia suggests that this cognitive dimension may be of nosological value. Poor insight has descriptive validity at the phenomenological and neuropsychological levels of schizophrenia and has prognostic validity in terms of the prediction of the course of illness. The lack of empirical data on the diagnostic specificity of poor insight to schizophrenia and the previous use of insight measures with questionable reliability and validity have limited this interpretation. METHODS: In the present study, we assessed insight into multiple aspects of mental disorder using a measure with demonstrated reliability and validity. A sample of 412 patients with psychotic and mood disorders coming from geographically diverse regions of the United States and one international site was studied. The main aims were to determine the prevalence of self-awareness deficits in patients in whom schizophrenia was diagnosed, to examine the relative severity of self-awareness deficits associated with schizophrenia compared with that of schizoaffective and mood disorders with and without psychosis, and to evaluate the clinical correlates of self-awareness in patients with schizophrenia. RESULTS: The results indicated that poor insight is a prevalent feature of schizophrenia. A variety of self-awareness deficits are more severe and pervasive in patients with schizophrenia than in patients with schizoaffective or major depressive disorders with or without psychosis and are associated with poorer psychosocial functioning. CONCLUSIONS: The results suggest that severe self-awareness deficits are a prevalent feature of schizophrenia, perhaps stemming from the neuropsychological dysfunction associated with the disorder, and are more common in schizophrenia than in other psychotic disorders.

Adaptation, Psychological↗

PubMed1994

Reversal of acute myelogenous leukemia in humanized SCID mice using a novel adoptive transfer approach.

Advanced human malignancies cannot be permanently cured by adoptive transfer of autologous lymphokine-activated killer (LAK) cells. Moreover, administration of high doses of IL-2 to maintain LAK activity in vivo is associated with severe toxicity. In this study, we tested the anti-tumor efficacy of a uniquely potent MHC non-restricted human killer T cell clone (TALL-104) in humanized severe combined immunodeficient (SCID) mice bearing acute myelogenous leukemia (AML). We show that, in appropriate experimental conditions, TALL-104 cells could effectively reverse the aggressive growth of the myelomonocytic leukemia cell line U937 in SCID mouse tissues, leading to complete abrogation of AML. A single transfer of TALL-104 cells at the time of tumor challenge in combination with recombinant human (rh) IL-12 (1 microgram/d) prolonged significantly the life of the mice. However, eradication of leukemia, as monitored both clinically and by PCR, was achieved by repeated injection of the effectors at close intervals. Complete cure was obtained also upon transfer of lethally irradiated (non-proliferating) TALL-104 cells together with low doses of rh IL-2 (100 U/d). Most notably, of the mice that received multiple transfers of TALL-104 cells without cytokines in an advanced disease stage, 50% were clinically cured, and 50% survived significantly longer. The potential of TALL-104 cells as an effective and safe leukemia purging agent is discussed.

Animals↗

PubMed1994

Additive effects of steel factor and antisense TGF-beta 1 oligodeoxynucleotide on CD34+ hematopoietic progenitor cells.

We previously demonstrated that TGF-beta 1 antisense oligodeoxynucleotides can release early CD34+ bone marrow progenitors from quiescence, and increase the numbers of mixed and large erythroid colonies. As Steel Factor (SF) has a similar effect on colony formation by CD34+ cells, we tested whether this factor acts by blocking the inhibitory effects of TGF-beta. That this is not generally the case was demonstrated by the finding that the combination of TGF-beta 1 antisense with SF in cultures of CD34+ bone marrow cells yielded enhanced colony formation that was more than additive when compared to cultures containing the single agents. This combination also yielded enhanced colony formation by CD34+ umbilical cord blood cells, but in this case, the effect was slightly less than additive. Thus in cord blood, some, but not all, of the progenitors that are maintained in quiescence by TGF-beta can be triggered into cycle by SF. However, the absolute number of CFU-GEMMs found in the antisense TGF-beta plus SF cultures of cord blood was 4-fold higher than that found in comparable bone marrow cultures. These data correlate well with our previous observations that umbilical cord blood contains 4-fold more CD34+ CD38- cells, the population found to respond to TGF-beta 1 antisense oligodeoxynucleotides.

Antigens, CD↗

PubMed1993

Stage-specific expression of c-kit protein by murine hematopoietic progenitors.

We have analyzed c-kit expression by hematopoietic progenitors from normal and 5-fluorouracil (5-FU)-treated mice by staining with monoclonal anti-c-kit antibody ACK-4. Marrow cells that were enriched for progenitors by a combination of metrizamide density separation and negative immunomagnetic selection with lineage-specific monoclonal antibodies (MoAbs) were separated into three populations based on the level of c-kit expression, c-kit(high), c-kit(low), and c-kit-. The majority of colony-forming cells from normal mice were in c-kit(high) population, whereas most of the progenitors from 5-FU-treated mice were in the c-kit(low) population. Optimal colony formation from c-kit(low) cells from 5-FU-treated mice required the interactions of at least two factors among interleukin-3 (IL-3), IL-11 and steel factor (SF) whereas colony formation from c-kit(high) cells of normal mice was supported well by IL-3 alone. Blast cells that were derived from 5-day culture of c-kit(low) post 5-FU cells were c-kit(high). These observations suggest that the primitive hematopoietic progenitors in cell cycle dormancy are c-kit(low) whereas actively cell cycling maturer progenitors are c-kit(high). Mature cells, with the exception of mast cells, derived from secondary culture of the c-kit(high) blast cells expressed little, if any, c-kit. These results are consistent with a model in which c-kit expression progresses from low levels on primitive, dormant multipotent progenitors to high levels on later, actively cycling progenitors, and finally, decreases to very low or undetectable levels on most mature blood cells, with the exception of mast cells.

Animals↗

PubMed1993

Progenitor cell hyperplasia with rare development of myeloid leukemia in interleukin 11 bone marrow chimeras.

Post 5-fluorouracil-treated murine bone marrow cells infected with a recombinant retrovirus (murine stem cell virus-interleukin 11 [MSCV-IL-11]) bearing a human IL-11 gene were transplanted into lethally irradiated syngeneic mice. Analysis of proviral integration sites in DNA prepared from hematopoietic tissues and purified cell populations of long-term reconstituted primary and secondary recipients demonstrated polyclonal engraftment by multipotential stem cells. High levels (100-1,500 U/ml) of IL-11 were detected in the plasma of the MSCV-IL-11 mice. Systemic effects of chronic IL-11 exposure included loss of body fat, thymus atrophy, some alterations in plasma protein levels, frequent inflammation of the eyelids, and often a hyperactive state. A sustained rise in peripheral platelet levels (approximately 1.5-fold) was seen throughout the observation period (4-17 wk). No changes were observed in the total number of circulating leukocytes in the majority of the transplanted animals (including 10 primary and 18 secondary recipients) despite a > 20-fold elevation in myeloid progenitor cell content in the spleen. The exceptions were members of one transplant pedigree which presented with myeloid leukemia during the secondary transplant phase. A clonal origin of the disease was determined, with significant expansion of the MSCV-IL-11-marked clone having occurred in the spleen of the primary host. Culturing of leukemic spleen cells from a quaternary recipient led to the establishment of a permanent cell line (denoted PGMD1). IL-11-producing PGMD1 myeloid leukemic cells are dependent on IL-3 for continuous growth in vitro and they differentiate into granulocytes and macrophages in response to granulocyte/macrophage colony-stimulating factor. The inability of autogenously produced IL-11 to support autonomous growth of PGMD1 cells argues against a mechanism of transformation involving a classical autocrine loop.

Animals↗

PubMed1993

Release from quiescence of CD34+ CD38- human umbilical cord blood cells reveals their potentiality to engraft adults.

Using optimal culture conditions in which the transforming growth factor beta 1 (TGF-beta 1) inhibitory loop has been interrupted by antisense TGF-beta 1 oligonucleotides or anti-TGF-beta serum, we have compared the proliferative capacities and the abilities of the CD34+ CD38- cell populations from bone marrow and umbilical cord blood to generate early progenitors in long-term cultures. The CD34+ CD38- fraction of umbilical cord blood accounts for 4% of the CD34+ fraction compared to only 1% in bone marrow, indicating that umbilical cord blood may be relatively enriched in stem cells. We estimate that the CD34+ CD38- cells from a typical umbilical cord blood sample produce equivalent numbers of colony-forming units (CFU)-granulocyte/erythrocyte/macrophage/megakaryocyte, twice as many CFU-granulocyte/macrophage (GM) and 3 times as many burst-forming units-erythroid as the same population from an average bone marrow sample used in adult transplantation. In addition, the colonies resulting from the umbilical cord blood samples were significantly larger than those from bone marrow, indicating a greater growth potential. However, the content of later progenitors, which may be important for short-term reconstitution, was less in umbilical cord blood-derived than in bone marrow-derived cell preparations, as estimated by a 4-fold lower production of CFU-GM in long-term cultures of CD34+ CD38+ cells. This deficit is partially compensated by the higher growth capacity of the resulting CFU-GM. These studies suggest that umbilical cord blood is a suitable source of cells for adult transplantation.

ADP-ribosyl Cyclase↗

PubMed1993

Cellular and molecular mechanisms of activation of MHC nonrestricted cytotoxic cells by IL-12.

Freshly separated PBL and two IL-2-dependent clonal T cell lines (TALL-103/2 [TCR-gamma delta+] and TALL-104 [TCR-alpha beta+]) were used to dissect, at the cellular and molecular levels, the mechanisms governing the enhancing effects of IL-12 on MHC nonrestricted cytotoxic activity. IL-12 induced cytotoxicity both in PBL and TALL cells, although less efficiently than IL-2, and the two cytokines displayed additive effects. Unlike IL-2, IL-12 failed to enhance the CD3 or CD2 redirected killing of the TALL cell lines. Analysis of the percentage of E/T conjugates induced by these cytokines showed that IL-12 could increase PBL, but not TALL cell, binding only when used in combination with IL-2. This and the failure of IL-12 to increase the expression of several adhesion molecules on PBL and TALL cells indicated no significant role for IL-12 in the binding step of the lytic interaction. We also excluded that production of TNF-alpha, IFN-gamma, or IL-2 by the IL-12-activated effectors might account for the cytotoxicity-inducing effects of this cytokine. By contrast, IL-12 was found to induce cytotoxic granule formation in PBL and TALL cells and to up-regulate the expression of their cytolytic components, including perforin, serine esterases, and TIA-1, both at the protein and mRNA levels. The costimulatory action of IL-2 and IL-12 on granulogenesis and induction of cytolytic proteins correlated well with the additive effects on cytotoxicity. Studies with cyclohexamide and actinomycin D demonstrated that TALL cells but not PBL require de novo protein synthesis for expression of serine esterases and perforin mRNA after IL-2 and/or IL-12 stimulation, and that both cytokines act directly or indirectly at the transcriptional level. Overall, these data indicate that IL-12 acts mostly at a postbinding level of the lytic interaction, involving enhanced expression of cytotoxic mediators, and that IL-2 and IL-12 use partially distinct pathways to activate the MHC nonrestricted killer function of mature T cells and resting lymphocytes.

Cell Adhesion↗

PubMed1993

Expression of isoforms of the human receptor tyrosine kinase c-kit in leukemic cell lines and acute myeloid leukemia.

Because mutations in receptor tyrosine kinases may contribute to cellular transformation, studies were undertaken to examine c-kit in human leukemia. Isoforms of c-kit have been characterized in the human megakaryoblastic leukemia cell line M-07. Deletion of the four amino acids Gly-Asn-Asn-Lys in the extracellular domain represents an alternatively spliced isoform that has been shown by others, in mice, to be associated with constitutive receptor autophosphorylation (Reith et al, EMBO J 10:2451, 1991). Additional isoforms differ in the inclusion or exclusion of a serine residue in the interkinase domain, a region that contains the binding site for phosphatidylinositol 3-kinase. By RNase protection analysis, we have shown coexpression of the Gly-Asn-Asn-Lys+ and Gly-Asn-Asn-Lys- isoforms, with dominance of the Gly-Asn-Asn-Lys- transcript, in normal human bone marrow, normal melanocytes, a range of tumor cell lines, and the blasts of 23 patients with acute myeloid leukemia. Analysis of transcripts for the Ser+ and Ser- isoforms also showed coexpression in all normal and leukemic cells examined. The ratios of isoform expression for both the Gly-Asn-Asn-Lys and Ser variants were relatively constant, providing no evidence in the tumors examined that upregulation of one isoform contributes to the neoplastic process.

Amino Acid Sequence↗

PubMed1993

The structure and dynamics of the granulocyte macrophage colony-stimulating factor receptor defined by the ternary complex model.

Myeloid cell lines and primary leukemic myeloblasts express two classes of granulocyte macrophage colony-stimulating factor (GM-CSF) binding sites of high (Kd 20-50 pM) and low affinity (Kd 5-10 nM). High affinity binding is caused by the association of two chains, p80 alpha and p130 beta, whereas p80 alpha alone confers low affinity binding only. Furthermore interleukin-3 (IL-3) competes for the binding of GM-CSF to its high affinity receptor (for review see Nicola, N. A., and Metcalf, D. (1991) Cell 67, 1-4). In the present study, we took advantage of the perturbation of GM-CSF binding equilibrium by IL-3 to take a quantitative approach to analysis of the structure and dynamics of the GM-CSF receptor complex. First, cross-linking studies were performed at two concentrations of radioligand. At 200 pM, a concentration sufficient for near saturation of the high affinity binding site R1, the association between p80 alpha and p130 beta is stoichiometric, and the addition of IL-3 prevents the binding to both chains. At 5 nM, a concentration sufficient for half-occupancy of the low affinity binding site R2, IL-3 prevents cross-linking to the beta chain only. Second, GM-CSF saturation curves were analyzed both at equilibrium and under conditions of perturbation of the equilibrium by IL-3. In the presence of IL-3, the interaction of GM-CSF with its receptor is converted from high to low affinity binding. Computer modeling of binding data with a ternary complex model involving GM-CSF, p80 alpha, and p130 beta indicates that the model fits the data with accuracy and suggests that ligand binding stabilizes the interaction between p80 alpha and p130 beta by 3 orders of magnitude. Third, membrane solubilization dissociates p80 alpha and p130 beta whereas on ligand-stabilized preformed complexes, solubilization did not dissociate the two chains. Finally, upon addition of GM-CSF, there is an increase with time in the proportion of ligand bound to the high affinity receptor, at the expense of that bound to low affinity receptor, suggesting that stabilization of the ternary complex is a time-dependent process.

Binding Sites↗

PubMed1993

Establishment of a karyotypically normal cytotoxic leukemic T-cell line from a T-ALL sample engrafted in SCID mice.

Bone marrow (BM) cells from a child with an immature (CD3-) acute T lymphoblastic leukemia (T-ALL) bearing no chromosomal abnormalities failed to grow in long-term culture in the presence or absence of recombinant human (rh) growth factors but could be engrafted in severe combined immunodeficient (SCID) mice and induced leukemia. The leukemic cells recovered from the animal tissues could be adapted to grow in vitro in the presence of rh interleukin-2 (IL-2) and give rise to a growth factor-dependent cell line designated TALL-107. This cell line expresses T-cell-specific mature markers (CD2, CD3/T-cell receptor [TCR] alpha beta, CD8, CD56), and its growth can be inhibited by IL-4 of all the cytokines tested. Similar to the original leukemic blasts, TALL-107 cells are clonal, have rearranged TCR-beta, gamma, and delta loci, and a normal 46 XY karyotype. However, unlike the patient's BM cells, the TALL-107 cell line displays potent tumoricidal activity that is not major histocompatibility complex restricted. The magnitude of mRNA expression of perforin and serine esterases and of lytic activity depends on the doses of IL-2 added. TALL-107 cells can also be triggered by CD3- and CD2-specific monoclonal antibodies (MoAbs) to mediate reverse tumor cell lysis. In addition, this cell line produces high levels of interferon gamma and tumor necrosis factor alpha on stimulation with anti-CD3 and/or anti-CD2 MoAb both in the presence or absence of IL-2. The overall data indicate that the SCID mouse is able to support the functional maturation and expansion of a cytotoxic T-cell subset from some types of T-ALL.

Animals↗

PubMed1993

Effects of interleukin-11 on the proliferation and cell cycle status of myeloid leukemic cells.

Interleukin-11 (IL-11) is a pleiotropic cytokine with effects on many different targets. Within the hematopoietic system, the effects of IL-11 are largely manifest only through combination with other cytokines, including IL-3 and Steel factor (SF). In the present study, we addressed the question of IL-11 responsiveness within the different types of human leukemic cells, as well as the mechanism of action of IL-11 at the cellular level. Analysis of a panel of samples from different patients with acute myeloblastic leukemia (AML) and myeloid leukemic cell lines indicated that IL-11 alone was ineffective in supporting myeloid leukemic cell growth but frequently enhanced growth supported by IL-3, granulocyte-macrophage colony-stimulating factor (GM-CSF), or SF. In contrast, three acute pre-B lymphocytic leukemia (pre-B-ALL) and two acute T lymphocytic leukemia (T-ALL) lines failed to respond to IL-11 alone or when combined with other cytokines. The growth enhancement of IL-11 among the AML patient samples was dose dependent and remarkably constant with half-efficient concentrations in the range of 0.3 to 0.4 ng/mL. The thymidine suicide studies with the patient samples revealed that 40% to 50% of the blast cells were in S-phase when exposed for 16 hours to IL-3 and this level was increased to 70% to 90% in response to either IL-11 or IL-6. Our data suggest that the latter two interleukins act synergistically with the direct mitogenic factor, IL-3, in triggering AML blast-cell proliferation. Detailed analysis with several patient samples further revealed that SF and IL-11 both enhance IL-3-supported clonogenic growth of AML blasts and the combination of all three growth factors yields optimal growth. In contrast, IL-6 does not further enhance the effect of IL-11. These results indicate that SF and IL-11 enhance IL-3-dependent clonogenic growth through two distinct pathways, whereas IL-6 and IL-11 may trigger the same pathway.

Cell Cycle↗

PubMed1993

Growth factor requirement for survival in cell-cycle dormancy of primitive murine lymphohematopoietic progenitors.

We used enriched marrow cells from mice administered three doses of 150 mg/kg 5-fluorouracil (5-FU) 1, 3 and 7 days before they were killed to study the effects of different growth factors on the survival of primitive, cell-cycle dormant progenitors in culture. This cell population yielded substantially fewer colonies in response to single growth factors than corresponding preparations from day 2 post-5-FU bone marrow samples, and the majority of progenitors were multipotential in nature. These observations were consistent with the prediction that multiple cycles of 5-FU treatment would further enrich for primitive cells. With this cell population, we found that among all the factors tested, interleukin-3 (IL-3) and steel factor (SF) as single factors are the most effective in supporting survival of dormant primitive progenitors. Interleukin-6 (IL-6), granulocyte colony-stimulating factor (G-CSF), interleukin-11 (IL-11), interleukin-4 (IL-4), interleukin-1 alpha (IL-1 alpha), and tumor necrosis factor-alpha (TNF-alpha) also supported survival of a few progenitors, but much less effectively than either IL-3 or SF. The hematopoietic progenitors that survived for 1 week in liquid culture supplemented with either IL-3 or SF retained the capability to develop pre-B-cell colonies in secondary culture. Our results demonstrate that survival of dormant murine lymphohematopoietic cells in culture is dependent on the presence of specific growth factors, and that this growth factor requirement can be satisfied well by SF or IL-3.

Animals↗

PubMed1993

Human interleukin-4 inhibits proliferation of megakaryocyte progenitor cells in culture.

We studied the effects of recombinant human interleukin-4 (rhIL-4) on megakaryocyte colony formation from enriched hematopoietic progenitors. IL-4 strongly inhibited pure and mixed megakaryocyte colony formation in a dose-dependent manner. Formation of erythroid bursts, eosinophil colonies, and erythrocyte-containing mixed colonies was not affected by the addition of IL-4 as reported previously (Sonoda Y, et al; Blood 75:1615, 1990). Delayed addition experiments suggested that IL-4 acts on an early stage of proliferation of megakaryocyte progenitors. Neutralizing antibodies (antisera) prepared against transforming growth factor beta, tumor necrosis factor alpha, interferon alpha (IFN alpha), and IFN gamma did not affect the inhibitory effects of IL-4 on pure and mixed megakaryocyte colony formation. In addition, the inhibitory effects of IL-4 was also seen in serum-free cultures and in cultures containing highly enriched CD34+, HLA-DR+ cells as a target population. These results indicate that IL-4 may function as one of the negative regulators in human megakaryocytopoiesis in vitro.

Adult↗

PubMed1993

CSF-1 control of C-FMS expression in normal human bone marrow progenitors.

We have previously shown (Zhou et al: Blood, 72:1870, 1988) that IL3, added with low concentrations of CSF-1 (1 ng/ml) to normal human CD34+ enriched cells, promoted the development of various types of colonies including those containing immature monocytes. However, when high concentrations of CSF-1 (20 ng/ml) were added alone or together with IL3, smaller colonies with mature macrophages were found. Here we show by in situ hybridization that IL3 allows the development, from CD34+ cells, of a subpopulation of immature progenitors which express the CSF-1 receptor (c-fms) mRNA. The expression of c-FMS protein was also substantiated by immunocytochemical studies using anti-c-fms antibody. The percentage of c-fms positive cells peaked at day 7 and began to decrease thereafter. When anti-CSF-1 antibodies were included in the culture, the decrease in c-fms mRNA after day 7 was abrogated. This indicated that endogenous CSF-1 was produced as CD34+ cells developed into monocytes or progenitors of monocytes and that CSF-1 modulates c-fms expression. We further demonstrated that when a high dose of CSF-1 (20 ng/ml) was added at day 7 to IL3-stimulated CD34+ cells, a rapid down-regulation of c-fms mRNA and protein was seen. No down-regulation was observed with low concentration of CSF-1 (1 ng/ml). The possibility that different concentrations of CSF-1 could modulate the development of monocytic progenitors is discussed.

Bone Marrow↗

PubMed1993

Human stem cell factor (c-kit ligand) induces an autocrine loop of growth in a GM-CSF-dependent megakaryocytic leukemia cell line.

The M07e megakaryoblastic leukemia cell line is strictly dependent on either interleukin 3 (IL-3) or granulocyte-macrophage colony-stimulating factor (GM-CSF) for continuous growth. This study shows that recombinant human stem-cell factor (rhSCF) can completely replace these lymphokines in supporting the continued propagation of M07e cells mostly by eliciting GM-CSF secretion in this target. In fact, in short-term proliferation assays the stimulatory activity of SCF is blocked about 75% by a GM-CSF-specific serum. In addition, we could detect GM-CSF expression by SCF-stimulated M07e cells, both at the protein and mRNA levels. In contrast, SCF does not induce transcripts for any other cytokine to which M07e cells are responsive, including IL-2, IL-3, IL-4, and IL-6. Overall, these data show that the ability of SCF to support the growth of this megakaryocytic cell line is mediated mostly by the induction of an autocrine loop of activation involving GM-CSF production. The finding that SCF can stimulate GM-CSF secretion also in an IL-2-dependent T-lymphoblastic leukemia cell line indicates that SCF can act on cells of both myeloid and lymphoid lineages, and that the ability to induce cytokines in target cells represents an important aspect of its mechanism of action.

Cell Division↗

PubMed1993

Cytokine modulation of the susceptibility of acute T-lymphoblastic leukemia cell lines to LAK activity.

We studied the regulatory effects of various cytokines on the susceptibility to lymphocyte-mediated lysis of cell lines established from patients with acute T-lymphoblastic leukemia (T-ALL). None of the cytokines tested affected the sensitivity of these targets to natural killer activity. In contrast, specific cytokines, different for each cell line, enhanced the susceptibility to lymphokine-activated killer (LAK) cells, while interferon gamma (IFN)-gamma always induced resistance. The same cytokines that increased LAK susceptibility also induced proliferative responses. The TALL-101 cell line, which responded to granulocyte-macrophage colony-stimulating factor (GM-CSF) with increased susceptibility to lysis, and to IFN-gamma with resistance, was used as a model to analyze the mechanisms underlying these changes. Cold target inhibition and conjugate formation assays both indicated that the changes in LAK susceptibility were not at the level of effector-target (E/T) binding. Furthermore, no significant changes in surface expression of adhesion molecules involved in E/T binding were induced by either GM-CSF or IFN-gamma on TALL-101 cells. Finally, N-alpha-benzyloxycarbonyl-L-lysine thiobenzyl-esterase assays demonstrated no differences in the ability of these cytokines to trigger the secretion of cytolysins in the bound effectors compared to unstimulated cells. Taken together, these results suggest that the cytokine-modulated susceptibility to lysis of these T-ALL lines might occur at a post-binding stage with mechanisms involving an altered responsiveness to lytic factors.

Cell Division↗

PubMed1992

Interleukin-11 stimulates multiple phases of erythropoiesis in vitro.

Interleukin-11 (IL-11), a pleiotropic cytokine originally isolated from a primate bone marrow stromal cell line, has been shown to stimulate T-cell-dependent B-cell maturation, megakaryopoiesis, and various stages of myeloid differentiation, but to inhibit adipogenesis. Because stromal cells are essential for the maintenance of early hematopoietic progenitor cells in long-term culture, we investigated the effects of IL-11 on multipotent and erythroid precursors from murine bone marrow in vitro in suspension and semisolid cultures. Our results show that in the presence of IL-3 or c-kit ligand (KL), IL-11 has profound stimulatory effects on primitive multilineage hematopoietic progenitors, pre-CFC(multi), as well as on precursors representing various stages of erythroid differentiation observable in vitro, including CFC(multi), BFU-E, and CFU-E. In addition, the combination of KL with IL-11 also stimulated highly proliferative erythroid progenitors that yield remarkable macroscopic erythroblast colonies in culture. These results indicate that IL-11 is likely to play a pivotal role in early hematopoiesis and at multiple stages of erythropoiesis.

Animals↗