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Biomedical subjects

T A Davis

Publications and source records attributed to T A Davis.

At least 37 records · Page 2Linked to original sources
PubMed1999

Susceptibility or resistance to Leishmania infection is dictated by the macrophages evolved under the influence of IL-3 or GM-CSF.

Although enhanced monocytopoiesis is a hallmark of leishmaniasis, its significance in determining the course of the disease has not been addressed. While the number of granulocyte-macrophage colony-stimulating factor (GM-CSF)-secreting cells increases in the draining lymph nodes in a resistant mouse strain (C57BL/6) during disease, in a susceptible strain (BALB/c) the number of interleukin-3 (IL-3)-secreting cells increases. Treatment of BALB/c mice with anti-IL-3 antibody significantly reduces the disease score. Bone marrow macrophages derived under stimulation with IL-3 (IL-3-Mphi) or GM-CSF (GM-Mphi) differ functionally. GM-Mphi are significantly more responsive to IFN-gamma-induced augmentation and more refractory to IL-4-mediated suppression of anti-leishmanial activity than IL-3-Mphi. LPS-induced IL-12 and TNF-alpha secretion by both the susceptible and resistant strain-derived macrophage subsets are down-regulated. Despite down-regulation of IL-12 secretion, GM-Mphi favor expansion of IFN-gamma-secreting cells and IL-3-Mphi favor IL-6-dependent expansion of the IL-4-secreting Th subset. Adoptive transfer of leishmanial antigen-pulsed IL-3-Mphi and GM-Mphi prior to infection either aggravated or reduced the disease score, respectively, in BALB/c mice. Anti-IL-6 treatment reverted the Th subset profile not only in vitro but also in vivo, resulting in a reduced disease score in both infected BALB/c mice and IL-3-Mphi recipients. The disease score in IL-3-Mphi recipients is also reduced significantly after anti-IL-4 treatment.

Adoptive Transfer↗
PubMed1999

A comparative study of the cell cycle status and primitive cell adhesion molecule profile of human CD34+ cells cultured in stroma-free versus porcine microvascular endothelial cell cultures.

Porcine microvascular endothelial cells (PMVECs) plus cytokines support a rapid proliferation and expansion of human CD34+CD38- cells that are capable of multilineage engraftment within the bone marrow of a secondary host. CD34+CD38- cells contain the self-renewing, long-term culture-initiating cells (LTC-IC) that are ideal targets for retroviral gene transfer experiments. Previous experiments attempting retroviral infection of CD34+CD38- cells have failed partly because these cells do not enter cell cycle in response to cytokine combinations. In this study, we determined the cell cycle status and the cell adhesion molecule profile on purified CD34+ cells and the CD34+CD38- subset before and after ex vivo expansion on PMVECs. Purified human CD34+ cells were cocultured with PMVECs for 7 days in the presence of optimal concentrations of granulocyte/macrophage-colony-stimulating factor (GM-CSF) + interleukin (IL)-3 + IL-6 + stem cell factor (SCF) + Flt-3 ligand. The total CD34+ population and the CD34+CD38- subset increased 8.4- and 67-fold, respectively, with absolute increases in the number of colony-forming unit-granulocyte macrophage (CFU-GM) (28.2-fold), CFU-Mix (8.7 fold), and burst-forming unit-erythroid (BFU-E) (4.0-fold) progenitor cells. After 7 days of coculture with PMVECs, 44% of the CD34+CD38+ subset were found to be in G1, and 51% were in G2/S/M phase of the cell cycle. More remarkably, 53% of the CD34+CD38- subset were in G1, and 17% were in G2/S/M phase after 7 days of PMVEC coculture. In contrast, only 22% of the CD34+CD38- subset remaining after 7 days of stroma-free culture were in G1, and 6% were in G2/S/M phase. Despite the high level of cellular activation and proliferation induced by PMVEC coculture, the surface expression of adhesion molecules CD11a (LFA-1), CD11b, CD15s (sialyl-Lewis x), CD43, and CD44 (HCAM) on the total CD34+ population was maintained, and the surface expression of CD49d (VLA-4), CD54 (ICAM), CD58, and CD62L (L selectin) increased after ex vivo expansion. In contrast, CD34+ cells expanded on stroma-free cultures showed lower and more variable expression of CD62L and CD15s. These findings demonstrate that the primitive CD34+CD38- subset of marrow progenitor cells can be induced to enter cell cycle and can be significantly expanded ex vivo on a hematopoietic supportive microenvironment (PMVECs) while preserving the expression of cell adhesion molecules that may be important in stem cell homing and engraftment.

ADP-ribosyl Cyclase↗
PubMed1999

Myelopoietin, a chimeric agonist of human interleukin 3 and granulocyte colony-stimulating factor receptors, mobilizes CD34+ cells that rapidly engraft lethally x-irradiated nonhuman primates.

Myelopoietin (MPO), a multifunctional agonist of interleukin 3 and granulocyte colony-stimulating factor (G-CSF) receptors, was evaluated for its ability to mobilize hematopoietic colony-forming cells (CFC) and CD34+ cells relative to control cytokines in normal nonhuman primates. Additionally, the engraftment potential of MPO-mobilized CD34+ cells was assessed in lethally irradiated rhesus monkeys. Normal rhesus monkeys were administered either MPO (200 microg/kg/day), daniplestim (a high-affinity interleukin 3 receptor agonist) (100 microg/kg/day), G-CSF (100 microg/kg/day), or daniplestim coadministered with G-CSF (100 microg/kg/day each), subcutaneously for 10 consecutive days. The mobilization kinetics were characterized by peripheral blood (PB) complete blood counts, hematopoietic CFC [granulocyte-macrophage CFC (GM-CFC), megakaryocyte CFC (MK-CFC)], and the immunophenotype (CD34+ cells) of PB nucleated cells prior to and on day 3 to days 7, 10, 12, and 14, and at intervals up to day 28 following initiation of cytokine administration. A single large-volume leukapheresis was conducted on day 5 in an additional cohort (n = 10) of MPO-mobilized animals. Eight of these animals were transplanted with two doses of CD34+ cells/kg. A maximum 10-fold increase in PB leukocytes (white blood cells) (from baseline 7.8-12.3 x 10(3)/microL to approximately 90 x 10(3)/microL) was observed over day 7 to day 10 in the MPO, G-CSF, or daniplestim+G-CSF cohorts, whereas daniplestim alone stimulated a less than onefold increase. A sustained, maximal rise in PB-derived GM-CFC/mL was observed over day 4 to day 10 for the MPO-treated cohort, whereas the daniplestim+G-CSF, G-CSF alone, and daniplestim alone treated cohorts were characterized by a mean peak value on days 7, 6, and 18, respectively. Mean peak values for PB-derived GM-CFC/mL were greater for MPO (5,427/mL) than for daniplestim+G-CSF (3,534/mL), G-CSF alone (3,437/mL), or daniplestim alone (155/mL) treated cohorts. Mean peak values for CD34+ cells/mL were noted within day 4 to day 5 of cytokine administration: MPO (255/microL, day 5), daniplestim+G-CSF (47/microL, day 5), G-CSF (182/microL, day 4), and daniplestim (96/microL, day 5). Analysis of the mobilization data as area under the curve indicated that for total CFCs, GM-CFC, MK-CFC, or CD34+ cells, the MPO-treated areas under the curve were greater than those for all other experimental cohorts. A single, large-volume (3.0 x blood volume) leukapheresis at day 5 of MPO administration (PB: CD34+ cell/microL = 438 +/- 140, CFC/mL = 5,170 +/- 140) resulted in collection of sufficient CD34+ cells (4.31 x 10(6)/kg +/- 1.08) and/or total CFCs (33.8 x 10(4)/kg +/- 8.34) for autologous transplantation of the lethally irradiated host. The immunoselected CD34+ cells were transfused into autologous recipients (n = 8) at cell doses of 2 x 10(6)/kg (n = 5), and 4 x 10(6)/kg (n = 3) on the day of apheresis. Successful engraftment occurred with each cell dose. The data demonstrated that MPO is an effective and efficient mobilizer of PB progenitor cells and CD34+ cells, such that a single leukapheresis procedure results in collection of sufficient stem cells for transplantation and long term engraftment of lethally irradiated hosts.

Animals↗
PubMed1999

Of flux and flooding: the advantages and problems of different isotopic methods for quantifying protein turnover in vivo: I. Methods based on the dilution of a tracer.

The advantages and problems, both practical and theoretical, of isotope dilution approaches to the determination of whole-body and tissue protein turnover are discussed. It was concluded that: (1) measurements made on the basis of the labelling of plasma and breath are well suited to the measurement of body amino acid oxidation and balance, but because of the problem of inhomogeneity of the body amino acid pools, this approach generally underestimates protein turnover; (2) in investigations of nutritional effects on whole-body amino acid turnover, closer attention should be paid to first-pass splanchnic amino acid metabolism; (3) the trans-organ tracer balance method, particularly if combined with the measurement of tissue amino acid labelling, is a potentially useful approach to the simultaneous and dynamic measurement of both protein synthesis and degradation; (4) leucine may be the most generally useful label for tracer level studies of both whole-body and muscle protein synthesis, as recent studies have shown quite close isotopic equilibrium between muscle-free and tRNA-bound leucine pools.

Amino Acids↗
PubMed1999

Dexamethasone inhibits small intestinal growth via increased protein catabolism in neonatal pigs.

Our objective was to determine how dexamethasone (Dex) affects gastrointestinal protein metabolism and growth in neonatal pigs. Two-day-old pigs were given daily subcutaneous injections of either Dex (1 mg/kg body wt, n = 7) or saline (control, n = 6) for 7 days. In vivo protein synthesis was measured after 7 days with a bolus of [3H]phenylalanine. Tissue protein contents were measured in an initial control group of 2-day-old pigs and in control and Dex pigs after 7 days to estimate protein accretion and degradation. In control pigs, the protein accretion in the ileum was nearly sixfold greater than in the jejunum during the 7-day period. Dex nominally altered stomach growth but completely blocked the accretion of protein and DNA in the jejunum and ileum, with reduced villus height in the ileum. Dex increased the fractional protein degradation rate in the ileum (28%) and decreased the absolute protein synthesis rate in the jejunum and ileum by 17 and 21%, respectively. Dex resulted in a 40% lower total intestinal lactase activity compared with controls via reductions in both specific activity and tissue mass, especially in the ileum. Dex significantly decreased the circulating concentrations of insulin-like growth factor (IGF) I and IGF-binding protein (IGFBP)-1, -2, and -3. However, the tissue abundance of the IGF-I receptor in the stomach and ileum was greater in Dex pigs than controls. Our results suggest that Dex significantly inhibits small intestinal growth via both increased degradation and decreased synthesis of protein. Furthermore, the inhibition of intestinal growth resulted in significantly decreased lactose digestive capacity.

Animals↗
PubMed1999

Aminoacyl-tRNA and tissue free amino acid pools are equilibrated after a flooding dose of phenylalanine.

The flooding dose method, which is used to measure tissue protein synthesis, assumes equilibration of the isotopic labeling between the aminoacyl-tRNA pool and the tissue and blood free amino acid pools. However, this has not been verified for a phenylalanine tracer in an in vivo study. We determined the specific radioactivity of [(3)H]phenylalanine in the aminoacyl-tRNA and the tissue and blood free amino acid pools of skeletal muscle and liver 30 min after administration of a flooding dose of phenylalanine along with [(3)H]phenylalanine. Studies were performed in neonatal pigs in the fasted and refed states and during hyperinsulinemic-euglycemic-amino acid clamps. The results showed that, 30 min after the administration of a flooding dose of phenylalanine, there was equilibration of the specific radioactivity of phenylalanine among the blood, tissue, and tRNA precursor pools. Equilibration of the specific radioactivity of the three precursor pools for protein synthesis occurred in both skeletal muscle and liver. Neither feeding nor insulin status affected the aminoacyl-tRNA specific radioactivity relative to the tissue free amino acid specific radioactivity. The results support the assumption that the tissue free amino acid pool specific radioactivity is a valid measure of the precursor pool specific radioactivity and thus can be used to calculate protein synthesis rates in skeletal muscle and liver when a flooding dose of phenylalanine is administered.

Amino Acids↗
PubMed1999

Single-agent monoclonal antibody efficacy in bulky non-Hodgkin's lymphoma: results of a phase II trial of rituximab.

PURPOSE: A phase II trial was performed to evaluate the safety and efficacy of rituximab, a chimeric anti-CD20 monoclonal antibody, in patients with bulky (> 10-cm lesion) relapsed or refractory low-grade or follicular non-Hodgkin's lymphoma (NHL). PATIENTS AND METHODS: Thirty-one patients received intravenous infusions of rituximab 375 mg/m(2) weekly for four doses. All patients had at least one prior therapy (median, three; range, one to 13) and had progressive disease at study entry. Patients were a median of 4 years from diagnosis. RESULTS: No patient had treatment discontinued because of an adverse event. No patient developed human antichimeric antibody. The overall response rate in 28 assessable patients was 43% with a median time to progression of 8.1 months (range, 4.5 to 18.6+ months) and median duration of response of 5.9 months (range, 2.8 to 12.1+ months). The average decrease in lesion size in patients who achieved a partial response was 76%, and patients with stable disease had a decrease in average lesion size of 26%. Median serum antibody concentration was higher in responders compared with nonresponders, and a negative correlation was shown between antibody concentration and tumor bulk at baseline. CONCLUSION: Rituximab single-agent outpatient therapy is safe and shows significant clinical activity in patients with bulky relapsed or refractory low-grade or follicular B-cell NHL.

Adult↗
PubMed1999

Therapy of B-cell lymphoma with anti-CD20 antibodies can result in the loss of CD20 antigen expression.

Rituximab is a chimeric antibody with human gamma-1 and kappa constant regions and murine variable regions. It recognizes the CD20 antigen, a pan B-cell marker. Therapeutic trials in patients with B-cell non-Hodgkin's lymphoma (NHL) have shown significant efficacy with a primary response rate of 50%, and a secondary response rate of 44% after repeat treatments in prior responders. The selection for proliferating tumor cells that no longer express CD20 may compromise repeated treatment. We have identified a patient who developed a transformed NHL that lost CD20 protein expression after two courses of therapy with rituximab. In a pretreatment lymph node biopsy, 83% of B cells (as defined by CD19 and surface immunoglobulin) expressed surface CD20. A biopsy from the recurrent tumor after two courses of rituximab revealed a diffuse large cell NHL where 0% of B cells expressed CD20 with no evidence of bound rituximab. Cytoplasmic staining showed no CD20 protein. Sequencing of immunoglobulin heavy chain cDNA identified identical variable sequences in the initial and recurrent lymphomas, confirming the association between the two tumors. Literature and database review suggests that approximately 98% of diffuse large cell lymphomas express CD20, which suggests that these tumors rarely survive without CD20. This is the first identified case of loss of CD20 expression in a lymphoma that has relapsed after rituximab therapy, although several other cases have since been identified. Considering the significant number of patients treated with anti-CD20 antibodies, this may occur only rarely and is unlikely to preclude recurrent therapy with anti-CD20 antibodies in the majority of patients. However, because many patients have relapsed after anti-CD20 antibody therapy and have not been biopsied to identify clones with down-regulated CD20 antigen, we do not currently know the true frequency of this phenomenon. When possible, patients should undergo evaluation for CD20 expression before repeated courses of anti-CD20 therapy.

Antibodies, Monoclonal↗
PubMed1998

Anti-idiotype antibodies can induce long-term complete remissions in non-Hodgkin's lymphoma without eradicating the malignant clone.

The immunoglobulin on the surface of B-cell lymphomas can be a tumor-specific target for monoclonal antibody therapy. Between 1981 and 1993, 45 individuals with low grade B-cell lymphoma were treated with 52 courses of custom-made anti-idiotype antibodies. The antibodies were used either alone or in combination with alpha-interferon, chlorambucil, or interleukin-2 (IL-2). The majority of these patients responded to treatment, with a 66% overall and 18% complete response rate. Six patients (13%) experienced prolonged complete remissions, five of which are ongoing from 4 to 10 years after therapy and are the subject of this report. We asked whether residual lymphoma could be found in these patients with prolonged remissions. We performed enzyme-linked immunosorbent assay (ELISA) assays for idiotype protein or anti-idiotype antibodies in serum. Blood and bone marrow samples were examined by flow cytometry for idiotype positive cells, and by polymerase chain reaction (PCR) for clonal gene rearrangements of immunoglobulin CDR3 sequences or t(14;18) translocations. Using these sensitive and specific tests it was possible to detect very low levels of residual lymphoma in five of these patients who had been in clinical remission for 3 to 8 years before this evaluation. These five have continued without recurrence for up to 3 years since. Thus, we have found a pattern of residual inactive disease in patients treated with anti-idiotype antibodies. The biology of follicular lymphoma evidently includes the potential for tumor dormancy after therapies with varied mechanisms of action, resulting in clinical inactivity for many years. Thus, long-term control of the disease is possible at a clinical level despite persistence of the malignant clone.

Animals↗
PubMed1998

Phorbol esters induce differentiation of human CD34+ hemopoietic progenitors to dendritic cells: evidence for protein kinase C-mediated signaling.

The intracellular signals that mediate the differentiation of pluripotent hemopoietic progenitors to dendritic cells (DC) are largely undefined. We have found that the phorbol ester PMA by itself induced 47% +/- 8.7% of input human CD34+ hemopoietic progenitors to differentiate into cells with morphology and surface Ag phenotype characteristic of DC by day 7 of culture. Functionally, PMA-generated DC processed and presented whole soluble Ag and also induced resting T cell proliferation and Ag-specific CTL effector function. Unlike cytokine-driven DC differentiation, PMA suppressed proliferation and induced cell death (in part via apoptosis) in cells that did not differentiate to DC. The effects of PMA were blocked by inhibitors of protein kinase C activation, suggesting a central role for this signaling molecule. PMA-mediated signaling also induced expression of the RelB transcription factor, an NF-kappaB family member implicated in DC differentiation. These findings suggest that phorbol esters activate protein kinase C, which then initiates the terminal component of an intracellular signaling pathway(s) involved in the DC differentiation of CD34+ hemopoietic progenitors.

Antigen Presentation↗
PubMed1998

Free amino acids in milks of human subjects, other primates and non-primates.

Preterm and term transitional milks of human subjects and mature milks of human subjects, non-human primates and non-primates were analysed for free amino acids (AA) using precolumn phenylisothiocyanate derivatization and liquid chromatography. Differences in free AA between three types of human milk were small. Milks of pinnipeds (seals and sea lions) contained the highest levels of total free AA (8634-20,862 mumol/l), while the milks of cows and sheep had the lowest levels of total free AA (1061-1357 mumol/l). The milks of human subjects, chimpanzees (Pan troglodytes), gorillas (Gorilla gorilla), elephants (Elephas maximus), horses and pigs had intermediate levels of total free AA (3069-7381 mumol/l). Glutamic acid was the most abundant free AA in milks of human subjects (1339-2157 mumol/l), non-human primates (423-2528 mumol/l), elephants (1332 mumol/l), horses (1119 mumol/l), and cows (349 mumol/l). Taurine was the most abundant free AA in milks of pinnipeds (5776-13,643 mumol/l), pigs (1238 mumol/l), goats (1150 mumol/l) and sheep (341 mumol/l). Taurine was the second most abundant free AA in milks of human subjects and non-human primates, while histidine was the second most abundant free AA in milks of pinnipeds. Milks of each species had a distinctive free AA pattern which may reflect the relative importance of the free AA during early postnatal development.

Amino Acids↗
PubMed1998

Amino acid metabolism and the energetics of growth.

The nonessential amino acids are involved in a large number of functions that are not directly associated with protein synthesis. Recent studies using a combination of transorgan balance and stable isotopic tracers have demonstrated that a substantial portion of the extra-splanchnic flux of glutamate, glutamine, glycine and cysteine derives from tissue synthesis. A key amino acid in this respect is glutamic acid. Little glutamic acid of dietary origin escapes metabolism in the small intestinal mucosa. Furthermore, because glutamic acid is the only amino acid that can be synthesized by mammals by reductive amination of a ketoacid, it is the ultimate nitrogen donor for the synthesis of other nonessential amino acids. Because the synthesis of glutamic acid and its product glutamine involve the expenditure of adenosine triphosphate (ATP), it seems possible that nonessential amino acid synthesis might have a significant bearing on the energetics of protein synthesis and, hence, of protein deposition. This paper discusses the topic of the energy cost of protein deposition, considers the metabolic physiology of amino acid oxidation and nonessential amino acid synthesis, and attempts to combine the information to speculate on the overall impact of amino acid metabolism on the energy exchanges of animals.

Adenosine Triphosphate↗
PubMed1998

Roles of insulin and amino acids in the regulation of protein synthesis in the neonate.

Neonates deposit protein at a very high rate and efficiently utilize dietary amino acids for protein deposition. This high efficiency is associated with an elevated stimulation of tissue protein synthesis by feeding. Our recent studies have focused on identification of the factors that mediate this response in the neonate. A positive curvilinear relationship between skeletal muscle protein synthesis and plasma insulin concentration was identified in fasted and fed suckling pigs; the relationship changes with development. To test the specific effects of insulin on protein metabolism in the neonate, a procedure to clamp amino acids, under hyperinsulinemic conditions, was developed. By using this technique, we showed that insulin-stimulated whole-body amino acid disposal is elevated in the neonate, and this response may account for the efficient use of dietary amino acids for protein accretion. More recent studies suggest that the enhanced stimulation of skeletal muscle protein synthesis by feeding in the neonate is primarily insulin mediated; however, the stimulation of liver protein synthesis by feeding seems to be largely a function of amino acid concentration.

Amino Acids↗
PubMed1998

Advances in the management of Hodgkin's and non-Hodgkin's lymphoma.

Recent developments in the management of lymphoma continue to refine our approach to the disease. There is increasing acceptance of the International Lymphoma Study Group classification for non-Hodgkin's lymphoma. Identification of a new viral agent associated with certain subtypes of lymphoma and new immunologic therapies change our perspective on the disease. New data on treatment results further elucidate the role of radiotherapy and high-dose therapy in Hodgkin's disease and the non-Hodgkin's lymphomas.

Hodgkin Disease↗
PubMed1998

Exogenous growth hormone stimulates somatotropic axis function and growth in neonatal pigs.

We studied the effects of exogenous porcine growth hormone (pGH) administration on circulating insulin-like growth factor I (IGF-I) concentration, IGF-binding proteins (IGFBP), tissue growth, and protein synthesis in neonatal pigs. One-day-old pigs were given daily intramuscular injections of either pGH (1 mg/kg body wt) (n = 6) or saline (n = 5) for 7 days, after which time we measured in vivo protein synthesis using a bolus of [3H]-phenylalanine. Mean plasma pGH concentration in pGH-treated pigs measured on day 7 was 22-fold higher than in controls. The plasma IGF-I concentration in pGH-treated pigs was significantly greater than in controls after 1 day of treatment and plateaued at 285% of control values after 4 days. After 7 days of treatment, plasma IGFBP-3 concentrations and the plasma glucose response to a meal were also greater in pGH-treated than control pigs. pGH treatment significantly increased body weight gain and food conversion efficiency and the protein synthesis rate in several visceral organs. Our results demonstrate that exogenous pGH increases circulating IGF-I and IGFBP-3 concentrations and visceral organ growth in neonatal pigs, suggesting that the somatotrophic axis is functional in the neonate.

Animals↗
PubMed1998

Response of skeletal muscle protein synthesis to insulin in suckling pigs decreases with development.

The elevated rate of muscle protein deposition in the neonate is largely due to an enhanced stimulation of skeletal muscle protein synthesis by feeding. To examine the role of insulin in this response, hyperinsulinemic-euglycemic-amino acid clamps were performed in 7- and 26-day-old pigs. Pigs were infused with 0, 30, 100, or 1,000 ng . kg-0.66 . min-1 of insulin to mimic the plasma insulin levels observed under fasted, fed, refed, and supraphysiological conditions, respectively. Whole body amino acid disposal was determined from the rate of infusion of an amino acid mixture necessary to maintain plasma essential amino acid concentrations near their basal fasting levels. A flooding dose of L-[4-3H]phenylalanine was used to measure skeletal muscle protein synthesis. Whole body amino acid disposal increased progressively as the insulin infusion rate increased, and this response was greater in 7- than in 26-day-old pigs. Skeletal muscle protein synthesis was stimulated by insulin, and this response was maximal at a low insulin infusion rate (30 ng . kg-0.66 . min-1). The stimulation of muscle protein synthesis by insulin was also greater in 7- than in 26- day-old pigs. These data suggest that muscle protein synthesis is more sensitive to insulin than whole body amino acid disposal. The results further suggest that insulin is a central regulatory factor in the elevated rate of muscle protein deposition and the increased response of skeletal muscle protein synthesis to feeding in the neonate.

Amino Acids↗
PubMed1998

Inhibition of human mast cell growth and differentiation by interferon gamma-1b.

In an effort to identify cytokines that inhibit human mast cell growth, we cultured HMC-1 cells and recombinant human stem cell factor (rhSCF)-dependent human bone marrow-derived mast cells (HBMCs) in the presence of interferon gamma (IFNgamma)-1b and interferon alpha (IFNalpha)-2b. HMC-1 cell numbers decreased in the presence of 1000 U/mL IFNgamma-1b but were unaffected by 1000 U/mL of IFNalpha-2b. HBMCs were then cultured for 0 to 7 days with 100 ng/mL rhSCF and 10 ng/mL recombinant human IL-3 (rhIL-3), followed by culture in rhSCF and administration of either 1000 U/mL IFNalpha-2b or 1000 U/mL IFNgamma-1b. HBMCs appearing in cultures with rhSCF alone or in combination with IFNalpha-2b were virtually identical in number through 8 weeks of culture. In cultures supplemented with IFNgamma-1b, HBMCs significantly decreased in number and incidence of granular metachromasia by 4 to 5 weeks (p<0.001). Similar results were obtained when human marrow was cultured from day 0 with rhSCF and IFNgamma-1b. Mature rhSCF-dependent HBMCs were also cultured at 5 weeks with rhSCF alone or in combination with IFNgamma-1b. Compared with cells cultured in rhSCF, mature 5-week HBMC cultures treated with rhSCF plus IFNgamma-1b revealed a decrease in mast cells, and those mast cells that remained had fewer toluidine blue- and tryptase-positive granules after 5 to 8 weeks. FACS analysis of rhSCF plus IFNgamma-1b-treated mature HBMCs revealed increased c-kit and Fc(epsilon)RI expression. Mast cell releasibility was not increased. IFNgamma-lb was thus able to suppress mast cell growth from CD34+ cells, suggesting that this agent should be considered as a candidate cytokine for the treatment of disorders of mast cell proliferation.

Bone Marrow Cells↗