Iron Deficiency Anemia Associated with an Error of Iron Metabolism in Two Siblings: A Thirty Year Follow Up

For thirty years we have followed two siblings with apparent iron deficiency anemia in the setting of systemic iron overload. This report details their clinical courses, which have been surprisingly disparate. The female sibling has been more severely affected, requiring multiple transfusions. In contrast, the male sibling demonstrated apparent improvement at puberty. Although both have shown evidence of systemic iron overload for many years, neither has had significant end organ toxicity. We discuss the probable pathophysiology of their disorder, drawing from animal models with similar defects in iron uptake and utilization.

Evidence for linkage of familial Diamond-Blackfan anemia to chromosome 8p23.3-p22 and for non-19q non-8p disease

Diamond-Blackfan anemia (DBA) is a rare congenital hypoplastic anemia that usually presents early in infancy and is inherited in 10% to 20% of cases. Linkage analysis has shown that DBA in many of both dominant and recessive DBA families mapped to chromosome 19q13.2 leading to the cloning of a gene on chromosome 19q13.2 that encodes a ribosomal protein, RPS19. However, subsequently, mutations of the RPS19 gene have only been identified in 25% of all patients with DBA. This study analyzed 14 multiplex DBA families, 9 of which had 19q13.2 haplotypes inconsistent with 19q linkage. A genome-wide search for linked loci suggested the presence of a second DBA locus in a 26.4-centimorgan (cM) interval on human chromosome 8p. Subsequently, 24 additional DBA families were ascertained and all 38 families were analyzed with additional polymorphic markers on chromosome 8p. In total, 18 of 38 families were consistent with linkage to chromosome 8p with a maximal LOD score with heterogeneity of 3.55 at D8S277 assuming 90% penetrance. The results indicate the existence of a second DBA gene in the 26.4-cM telomeric region of human chromosome 8p23.3-p22, most likely within an 8.1-cM interval flanked by D8S518 and D8S1825. Seven families were inconsistent with linkage to 8p or 19q and did not reveal mutations in the RPS19 gene, suggesting further genetic heterogeneity. (Blood. 2001;97:2145-2150)

One-day ex vivo culture allows effective gene transfer into human nonobese diabetic/severe combined immune-deficient repopulating cells using high-titer vesicular stomatitis virus G protein pseudotyped retrovirus

Retrovirus-mediated gene transfer into long-lived human pluripotent hematopoietic stem cells (HSCs) is a widely sought but elusive goal. A major problem is the quiescent nature of most HSCs, with the perceived requirement for ex vivo prestimulation in cytokines to induce stem cell cycling and allow stable gene integration. However, ex vivo culture may impair stem cell function, and could explain the disappointing clinical results in many current gene transfer trials. To address this possibility, we examined the ex vivo survival of nonobese diabetic/severe combined immune-deficient (NOD/SCID) repopulating cells (SRCs) over 3 days. After 1 day of culture, the SRC number and proliferation declined twofold, and was further reduced by day 3; self-renewal was only detectable in noncultured cells. To determine if the period of ex vivo culture could be shortened, we used a vesicular stomatitis virus G protein (VSV-G) pseudotyped retrovirus vector that was concentrated to high titer. The results showed that gene transfer rates were similar without or with 48 hours prestimulation. Thus, the use of high-titer VSV-G pseudotyped retrovirus may minimize the loss of HSCs during culture, because efficient gene transfer can be obtained without the need for extended ex vivo culture.

Clinical research: perceptions, reality, and proposed solutions. National Institutes of Health Director's Panel on Clinical Research

CONTEXT

The proportion of investigators applying for clinical research grants from the National Institutes of Health (NIH) who are physicians has declined from 40% 30 years ago to 25% today.

OBJECTIVE

To recommend NIH policy changes that might encourage physician investigators to undertake careers in clinical research, eg, patient-oriented research, epidemiologic and behavioral studies, outcomes research, and health services research.

PARTICIPANTS

The NIH Director's Panel on Clinical Research comprised 14 physicians from academia and industry, chosen by the director. They met in numerous closed sessions and in 5 public meetings from July 1995 to November 1997.

CONSENSUS PROCESS

In addition to expert opinion and pertinent literature, data sources included the training characteristics of applicants to NIH who were funded or not. Topics considered included financing of clinical research, recruitment, training, and retention of future clinical investigators, conduct of clinical trials, and peer review of clinical research. Consensus was reached and recommendations were made in response to an interim report, widely circulated to the biomedical community, written by members of the panel, which contained preliminary recommendations.

CONCLUSIONS

The panel's final recommendations to NIH included maintaining at least the present proportion of NIH funding for clinical research; continuing mentored opportunities in clinical research for medical students; promoting clinical research training by offering didactic courses and grant opportunities in clinical research to nascent investigators emerging from specialty training programs and providing partial salary support for mentors; restructuring study sections that review patient-oriented research applications to include more physicians; encouraging clinical investigators and basic scientists to work closely together and weld collaborations between academic clinical investigators and colleagues in pharmaceutical and biotechnology companies; and developing a joint policy between academic health centers and NIH for the support of clinical research and clinical research training.

The beta chain of the interleukin-3 receptor functionally associates with the erythropoietin receptor

Interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) receptors share a common beta chain (beta(c)), and both cytokines enhance erythropoietin (Epo)-dependent in vitro erythropoiesis by primary hematopoietic progenitors and factor-dependent cells. These data suggest that the Epo receptor and beta(c) may functionally interact. To determine whether such interactions can be documented, we studied a murine factor-dependent cell line (Ba/F3), which endogenously expresses IL-3R. First, Ba/F3 cells were transfected with murine EpoR, making them responsive to both IL-3 and Epo. Next, the EpoR expressing cells were transfected with murine beta(c). This resulted in an enhanced sensitivity of these cells to Epo, which was especially pronounced at low Epo concentrations. Ba/F3-EpoR were then treated with antisense oligodeoxynucleotides to the murine beta. Control sense and nonsense had no effect on Epo-dependent growth, but the antisense markedly and specifically inhibited Epo-dependent growth. In contrast, the antisense did not affect beta-globin message levels (another Epo-responsive effect in these cells) detectable by Northern blot. Finally, Western blot analysis of proteins immunoprecipitated from cells expressing both receptors with antibody against beta and blotted with antibody against EpoR, or immunoprecipitated with antibody against EpoR and blotted with antibody against beta, showed that EpoR and beta coimmunoprecipitate. These data show that the beta chain functionally and physically associates with the EpoR. This suggests that these cytokine receptors exist as a large supercomplex and offers the first molecular explanation for the synergistic effects of IL-3 and GM-CSF with Epo during erythropoiesis.

The beta c component of the granulocyte-macrophage colony-stimulating factor (GM-CSF)/interleukin 3 (IL-3)/IL-5 receptor interacts with a hybrid GM-CSF/erythropoietin receptor to influence proliferation and beta-globin mRNA expression

BACKGROUND

The interaction of different members of the hematopoietic growth factor receptor family may be relevant to the increased proliferation and the failure of differentiation that characterizes the myeloid leukemias. We recently demonstrated that a chimeric receptor (GMER) that is composed of the extracellular and transmembrane domains of the human granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor alpha-chain (GMR alpha) and the cytoplasmic domain of the murine erythropoietin receptor mEpoR binds hGM-CSF with low affinity (3 nM) and confers both proliferative and differentiation signals to stably transfected murine Ba/F3 cells.

MATERIALS AND METHODS

To investigate whether the common beta-subunit of the GM-CSF receptor (beta c) can interact with GMER, either the entire beta-subunit or a mutant, truncated beta-subunit that completely lacks the cytoplasmic domain (beta tr) was introduced into Ba/F3 cells that express GMER, and the binding of GM-CSF as well as proliferation and differentiation responses were measured.

RESULTS

Scatchard analysis showed that both GMER + beta c and GMER + beta tr bound hGM-CSF with high affinity (Kd 40 pM to 65 pM). Proliferation assays showed that the maximum growth of cells expressing GMER + beta c was identical to that of cells with GMER alone. However, proliferation of the cells that expressed GMER + beta tr was reduced by 80-95% of GMER. Dose-response curves showed that the concentration of GM-CSF required for half-maximal growth was 0.5-5.0 pM for GMER + beta c and 0.5-5 nM for GMER and GMER + beta tr. The EpoR cytoplasmic domain of GMER also undergoes ligandinducible tyrosine phosphorylation. However, the tyrosine phosphorylation did not correlate with growth in cells expressing beta tr. Coexpression of beta c with GMER in Ba/F3 cells grown in hGM-CSF markedly enhanced beta-globin mRNA expression.

CONCLUSIONS

These results indicate that beta c can transduce a unique signal in association with GMER to influence both proliferative and differentiation signal pathways.

Cooperation between core binding factor and adjacent promoter elements contributes to the tissue-specific expression of interleukin-3

Tissue-specific expression of interleukin-3 (IL-3) is mediated via cis-acting elements located within 315 base pairs of the transcription start. This is achieved in part through the positive activities of the AP-1 and Elf-1 sites in the IL-3 promoter. The contribution to T cell-specific expression by other promoter sites was assessed in a transient expression assay with IL-3 promoter constructs linked to a luciferase gene, focusing initially on the core binding factor (CBF) site, which is footprinted in vivo upon T cell activation. Activity of the CBF site is shown to be critically dependent on the adjacent activator site Act-1. Together the Act-1 and CBF sites form a functional unit (AC unit) with dual activity. The AC unit is demonstrated to enhance basal activity of promoters both in fibroblasts and T cells. This activity is further inducible in activated T cells, but not in fibroblasts. In addition to the already identified NIP repressor site, evidence is presented for a second repressor region that restricts promoter activity in fibroblasts. Finally, a novel positive regulatory element has been mapped in the IL-3 promoter between nucleotide -180 and -210 that leads to increased expression in T cells. Together these results demonstrate that T cell expression of IL-3 is not specified by the activity of a single tissue-specific element, but instead involves multiple interacting elements that provide both specific positive regulation in T cells and specific negative regulation in fibroblasts.

Diamond-Blackfan anemia. Natural history and sequelae of treatment

To define further the natural history of treated Diamond-Blackfan anemia (DBA), a congenital anemia characterized by a paucity of erythroid precursors, we analyzed 76 patients diagnosed or followed at Children's Hospital, Boston, between 1931 and 1992. Although DBA is generally defined as macrocytic, we found that mean corpuscular volume in infants aged <5 months rarely exceeded the normal range and is of little diagnostic value. Macrocytosis in patients aged > or = 5 months was more striking. Nine of 16 patients who never received steroids experienced remissions, sometimes after years of transfusions. Thirty-one of 56 patients receiving corticosteroids responded. Of these 31, 13 experienced remissions, 11 remained steroid dependent and 7 later required transfusions. Most nonresponders maintained transfusion dependence. Patients frequently (64%) experienced treatment-related morbidity, most commonly hemosiderosis. The relative risk of leukemia was profoundly elevated (RR, 200; 95% CI, 54.5-512.1) and hematologic parameters at long-term follow-up were often abnormal. While potential responsiveness to steroids and relative ease of red cell transfusion make DBA one of the most treatable congenital marrow failure syndromes, both disease-related and treatment-related factors contributed to a limited prognosis (median survival, 38 years). Patients should be carefully monitored longitudinally for evidence of leukemia and adverse effects of therapy, and alternative treatment strategies should be considered on an individual basis.

Expression and function of the human granulocyte-macrophage colony-stimulating factor receptor alpha subunit

To determine the expression and function of the granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor alpha chain (GMR alpha) during hematopoiesis and on leukemic cells, monoclonal antibodies were raised by immunizing mice with cells expressing high levels of human GMR alpha. A pool of five antibodies isolated from three different mice was used to characterize GMR alpha. This antibody pool (anti-GMR alpha) immunoprecipitated a protein with the expected molecular weight of GMR alpha from COS cells transiently transfected with the GMR alpha gene. In factor-dependent cells, GMR alpha existed as a phosphoprotein. However, its phosphorylation was not stimulated by the presence of GM-CSF. Anti-GMR alpha inhibited the GM-CSF-dependent growth of cell lines and normal bone marrow cells and inhibited the binding of iodinated GM-CSF to its receptor. Cell surface expression of GMR alpha was examined using anti-GMR alpha and flow cytometry. GMR alpha was readily detectable on both blood monocytes and neutrophils. In adherence-depleted normal bone marrow, two separate populations expressed GMR alpha. The most positive cells were predominantly macrophages, whereas the cells that expressed less GMR alpha were largely myelocytes and metamyelocytes. A small population of lin-CD34+ or CD34+CD38- cells also expressed GMR alpha, but they were not capable of significant growth in colony-forming assays. In contrast, the majority of lin-CD34+ and CD34+CD38- cells were GMR alpha-, yet they produced large numbers of myeloid and erythroid colonies in the same assay. Malignant cells from patients with leukemia were also tested for GMR alpha expression. All of the myeloid leukemias and only rare lymphoid leukemias surveyed tested positive for GMR alpha. These results show that anti-GMR alpha is useful for the functional characterization of the GMR alpha and for the detection of myeloid leukemia and that GMR alpha is expressed on certain lineages throughout hematopoietic development; however, progenitors that express the receptor may have a reduced capacity to proliferate in response to hematopoietic growth factors.

Survival in medically treated patients with homozygous beta-thalassemia

BACKGROUND

The prognosis of patients with homozygous beta-thalassemia (thalassemia major) has been improved by transfusion and iron-chelation therapy. We analyzed outcome and prognostic factors among patients receiving transfusions and chelation therapy who had reached the age at which iron-induced cardiac disease, the most common cause of death, usually occurs.

METHODS

Using the duration of life without the need for either inotropic or antiarrhythmic drugs as a measure of survival without cardiac disease, we studied 97 patients born before 1976 who were treated with regular transfusions and chelation therapy. We used Cox proportional-hazards analysis to assess the effect of prognostic factors and life-table analysis to estimate freedom from cardiac disease over time.

RESULTS

Of the 97 patients, 59 (61 percent) had no cardiac disease; 36 (37 percent) had cardiac disease, and 18 of them had died. Univariate analysis demonstrated that factors affecting cardiac disease-free survival were age at the start of chelation therapy (P < 0.001), the natural log of the serum ferritin concentration before chelation therapy began (P = 0.01), the mean ferritin concentration (P < 0.001), and the proportion of ferritin measurements exceeding 2500 ng per milliliter (P < 0.001). With stepwise Cox modeling, only the proportion of ferritin measurements exceeding 2500 ng per milliliter affected cardiac disease-free survival (P < 0.001). Patients in whom less than 33 percent of the serum ferritin values exceeded 2500 ng per milliliter had estimated rates of survival without cardiac disease of 100 percent after 10 years of chelation therapy and 91 percent after 15 years.

CONCLUSIONS

The prognosis for survival without cardiac disease is excellent for patients with thalassemia major who receive regular transfusions and whose serum ferritin concentrations remain below 2500 ng per milliliter with chelation therapy.

Studies of hybrid hematopoietic growth factor receptors

To gain further insight into the mechanisms by which both granulocyte-macrophage-colony stimulating factor (GM-CSF) and erythropoietin receptors function, we have utilized a GM-CSF erythropoietin hybrid receptor with GM-CSF as the external domain and erythropoietin as the intracellular domain. Results show that the beta common GM-CSF receptor both enhances the affinity binding of GM-CSF to the receptor and plays an important role in signaling through the receptor. A truncated form of the beta common receptor actually acts as a dominant negative regulatory factor.

Evaluation of granulocyte-macrophage colony-stimulating factor for treatment of pancytopenia in children with fanconi anemia

Fanconi anemia is a congenital syndrome characterized by multiple specific physical anomalies, progressive marrow failure, and a predisposition to acute leukemia. We studied the toxicity and efficacy of daily subcutaneous administration of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) in patients with Fanconi anemia and pancytopenia. The toxicity of GM-CSF at the doses and schedule used was minimal. Six of seven patients entered had an increase in the neutrophil count of 7- to 25-fold, which was maintained during the course of study. Despite increases in the reticulocyte count, increases in hemoglobin concentration were rare. No improvement in platelet count was evident in any patient. No patient has evidence of leukemia after up to 19 months of continuous GM-CSF exposure, and all five surviving patients remain responsive to treatment. Although the optimal dose, schedule, and choice of cytokine for patients with marrow failure and Fanconi anemia are not established by this preliminary study, the data indicate that (1) GM-CSF may be able to palliate at least the neutropenia and potentially the neutropenic complications of the disease, (2) this effect can be sustained for more than 1 year, and (3) rapid evolution of acute leukemia is unlikely to be a frequent outcome of such treatment. The clinical impact of GM-CSF or other cytokines in patients with Fanconi anemia and pancytopenia remains to be established by further studies.

Effects of interleukin-3 and granulocyte-macrophage colony-stimulating factor on thrombopoiesis in congenital amegakaryocytic thrombocytopenia

Amegakaryocytic thrombocytopenia (AMT) is a rare and often fatal disorder of infancy and childhood presenting with isolated thrombocytopenia that progresses to marrow failure. The defect in thrombopoiesis is not well understood nor is the etiology of the progressive marrow failure. No standard modality of treatment exists. Here, we evaluated the capacity of marrow cells isolated from five patients with AMT and progressive marrow failure to generate megakaryocyte progenitor cells (CFU-MK). These in vitro studies demonstrated assayable numbers of CFU-MK from all patient bone marrows that responded in vitro to the addition of interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), or the combination of both. These findings suggest that the defect in AMT might be partially correctable by the administration of these cytokines. A Phase I/II trial of in vivo administration of these same hematopoietins in the identical patients was conducted in which no significant toxicity was observed. IL-3 but not GM-CSF administration resulted in improved platelet counts in two patients and decreased bleeding and transfusion requirement in the remaining three. No clinical benefit was observed when GM-CSF was administered after IL-3 pretreatment. Prolonged IL-3 administration has resulted in platelet increases in an additional two patients. In vitro responsiveness of CFU-MK to either cytokine did not predict the degree of clinical response. Although the optimal dose and schedule of IL-3 either alone or in combination remains to be established, this study suggests that IL-3 may contribute to the treatment of patients with AMT.

Interleukin-3 expression by activated T cells involves an inducible, T-cell-specific factor and an octamer binding protein

Interleukin-3 (IL-3) is exclusively expressed by activated T and natural killer cells, a function that is tightly controlled both in a lineage-specific and in a stimulation-dependent manner. We have investigated the protein binding characteristics and functional importance of the ACT-1-activating region of the IL-3 promoter. This region binds an inducible, T-cell-specific factor over its 5' end, a site that is necessary for the expression of IL-3 in the absence of other upstream elements. Over its 3' end, it binds a factor that is ubiquitously and constitutively expressed. This factor is Oct-1 or an immunologically related octamer-binding protein, and it plays a role in coordinating the activity of several regulatory elements. These characteristics make the ACT-1 site analogous to the activating ARRE-1 site in the IL-2 promoter. Furthermore, and despite a lack of sequence homology, the promoters of IL-3 and IL-2 share an organizational pattern of regulatory elements that is likely to be important for the T-cell-specific expression of these genes.

A low-affinity human granulocyte-macrophage colony-stimulating factor/murine erythropoietin hybrid receptor functions in murine cell lines

To identify domains in hematopoietic growth factor receptors that are important for signal transduction, a hybrid receptor (GMER) was constructed by splicing the DNA of the entire extracellular and transmembrane domains of the human granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor alpha 2 subunit (GMR) to the cytoplasmic domain of the murine erythropoietin receptor (mEpoR). The hybrid receptor was introduced into the interleukin-3 factor-dependent murine hematopoietic cell line Ba/F3. Cells that expressed high receptor numbers were selected by cell sorting using phycoerythrin-labeled human GM-CSF. Immunoprecipitation of GMER from Ba/F3 cells showed a band with an Mr of 105,000 daltons. Human GM-CSF binding to Ba/F3 cells that expressed GMER showed a kd of 3.0 nmol/L and 475 binding sites/cell, while the same cells that expressed GMR had 300 sites/cell and a kd of 3.5 nmol/L. The proliferative response to GM-CSF of Ba/F3 cells that expressed GMER showed 1/2 maximal cell growth (as measured by 3H-thymidine incorporation) at a GM-CSF concentration of 2.5 x 10(-8) mol/L. When cultured in human GM-CSF, Ba/F3-GMER cells expressed cell surface glycophorin. Similar results were obtained with Ba/F3 cells transfected with the mEpoR and cultured in erythropoietin. Expression of GMR plus the human GM-CSF receptor beta chain in the same cell line also resulted in human GM-CSF stimulated proliferation; however, cell surface glycophorin was not detected. These data show that a low-affinity GM-CSF/Epo hybrid receptor can promote GM-CSF-dependent proliferation and can induce the expression of glycophorin, an erythroid-specific protein.

The production of steel factor mRNA in Diamond-Blackfan anaemia long-term cultures and interactions of steel factor with erythropoietin and interleukin-3

Diamond-Blackfan anaemia (DBA) is a congenital macrocytic anaemia. To investigate whether DBA is due to hyporesponsiveness to or hypoproduction of Steel factor (SF), we compared the in vitro responsiveness of the BFU-E contained in the Ficoll-Hypaque non-adherent cell fraction of six DBA marrows with that of four normal marrows and one transient erythroblastopenia of childhood (TEC) marrow. In addition, we studied the effect of soluble SF on long-term marrow cultures (LTMC) and analysed the stromal cells from these cultures for SF mRNA transcripts. All the patients showed an erythropoietin dose-related increase of small BFU-E. The number and size of BFU-E was increased with the addition to the epo of IL-3 or SF; IL-3+SF was not synergistic. The addition of soluble SF to LTMC of DBA patients was associated with a small but consistent increase in non-adherent cell production and an increase in the number of progenitors. Messenger RNA from immortalized stromal cell lines of three patients and from primary bone marrow stromal cells of one patient showed the presence of expected SF transcripts by PCR analysis. These results demonstrate that this group of DBA patients responds to SF and produces SF mRNA normally, indicating that SF itself is not involved in DBA pathophysiology. The effects observed suggest that, despite the lack of evidence for a causative role, SF may prove to be effective treatment for such patients.

Hydroxyurea-induced HbF production in anemic primates: augmentation by erythropoietin, hematopoietic growth factors, and sodium butyrate

Hydroxyurea, a cell-cycle-specific cytotoxic agent, has been shown to increase fetal hemoglobin (HbF) production. This property makes it an attractive drug for treatment of sickle cell disease and severe beta thalassemia. Its potential efficacy is limited because of a variable and often suboptimal response. Combinations of hydroxyurea and other drugs may induce more clinically significant increases in HbF. We have utilized chronically phlebotomized rhesus monkeys, treated with oral hydroxyurea, to investigate the capacity of several other agents to further augment HbF synthesis. Recombinant human erythropoietin, in super-pharmacologic doses, increased F-reticulocyte production when given on a weekly sequential schedule (3 of 7 days) with hydroxyurea (4 of 7 days), but it was less effective on an alternate day schedule when hydroxyurea was given daily. Neither recombinant human interleukin 3 (IL-3) nor recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF), when infused individually, increased F-reticulocytes in animals receiving daily hydroxyurea. Sequential, overlapping infusions of IL-3 and GM-CSF produced a small but statistically significant increase in F-reticulocytes in one of two hydroxyurea-treated animals. Infusions of sodium butyrate produced a substantial augmentation in F-reticulocyte production in animals chronically treated with hydroxyurea. Thus, our studies have identified several agents that may prove useful in combination with hydroxyurea to achieve clinically beneficial levels of HbF.

Enhanced expression of interleukin-3 and granulocyte-macrophage colony-stimulating factor receptor subunits in murine hematopoietic cells stimulated with hematopoietic growth factors

AIC2A and AIC2B are closely related genes encoding components of the receptors for murine interleukin-3 (IL-3) (AIC2A) and granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-5 (AIC2B). We have studied the parallel regulation of expression of these genes in erythroid and myeloid progenitor cell lines. AIC2A and AIC2B transcription was transiently induced in these cells in response to a variety of hematopoietic growth factors, including erythropoietin (EPO), monocyte-CSF, IL-3, GM-CSF, and stem cell factor (SCF or kit ligand). Run-on assays established that the increase occurred mainly at the transcriptional level. Immunoprecipitation experiments confirmed that the increase in messenger RNA expression resulted in augmented synthesis of both AIC2A and AIC2B proteins, and binding studies further showed these proteins to be functional. We observed a fourfold increase in low-affinity IL-3 sites in an erythroid precursor cell line stimulated with EPO, and a threefold increase in GM-CSF high-affinity sites in a myeloid cell line stimulated with IL-3. In addition, we showed that the increase in the IL-3 receptor chain AIC2A in the erythroid precursor cell line correlated with the ability of IL-3 to exert a cooperative effect with EPO in the induction of beta-globin in these cells.

A service chief model for general pediatric inpatient care and residency training

Pediatric training programs are faced with rapid, fundamental changes in hospital practice and an increasingly rigorous regulatory and fiscal environment. Traditional models for providing care and teaching students and house officers may not be sufficiently responsive to these challenges. In 1986, the Department of Medicine at Children's Hospital, Boston, reorganized the general inpatient program and implemented a "service chief" system adapted from British hospital "firms." Three age-based inpatient services (Thomas Morgan Rotch infant/toddler service, Kenneth Daniel Blackfan school-age service, and Charles Alderson Janeway adolescent/young adult service) were created, each headed by an experienced clinician and teacher (service chief). The service chiefs developed age-appropriate curricula, recruited a balanced faculty of generalists and specialists to serve as attending physicians and provide teaching in their areas of expertise, and established strong collaborative relationships with nurse managers on their respective wards. Implementation of the service chief system has been associated with development of faculty esprit de corps, standardized tracking of faculty performance, enhanced supervision and counseling of housestaff, and improved continuity of patient care. Relationships with referring physicians have improved dramatically, as measured by formal satisfaction surveys. Accountability and documentation have been emphasized, and departmental billings have increased sharply. Ongoing quality indicators have been developed, and collaborative patient care, teaching, and quality-improvement projects have been initiated with the nursing staff. Naming the services for distinguished past physicians-in-chief has provided a focus for fund-raising.(ABSTRACT TRUNCATED AT 250 WORDS)

A functional isoform of the human granulocyte/macrophage colony-stimulating factor receptor has an unusual cytoplasmic domain

The granulocyte/macrophage colony-stimulating factor (GM-CSF) receptor (GMR) transduces a signal that results in the proliferation, differentiation, and functional activation of hematopoietic cells. This study sought to determine whether functional isoforms of the receptor exist that may be important in generating this diversity of cellular response. We have isolated a cDNA encoding an isoform of the low-affinity human GMR that is a product of alternative splicing of the GMR gene and results in a predicted 410-amino acid protein with a cytoplasmic domain that is rich in serine residues, a feature of regions critical in signal transduction for other receptors of the hematopoietin receptor superfamily. This receptor bound ligand and was functionally active when introduced into a murine factor-dependent cell line; mRNA transcripts representative of this isoform were coexpressed with those for a previously isolated 400-amino acid isoform of the GMR in normal hematopoietic and leukemic cells. In view of the recent isolation of a cDNA, designated GM-CSF R beta, that confers high-affinity binding of GM-CSF in cotransfection experiments with the low-affinity receptor, we suggest that the previously isolated low-affinity receptor be designated GM-CSF R alpha 1 and the one described in this report be designated GM-CSF R alpha 2.

Restoration of phagocyte function by interferon-gamma in X-linked chronic granulomatous disease occurs at the level of a progenitor cell

Phagocytes from X-linked chronic granulomatous disease (X-CGD) patients are deficient in their ability to generate superoxide because of a defective gene that encodes a heavy chain of cytochrome b, a critical component in the superoxide-generating pathway. Previously we have shown that a single in vivo treatment of selected X-CGD patients with interferon-gamma (INF-gamma) resulted 14 days later in near-normal levels of superoxide generation by phagocytes. The effect persisted for 28 days. This prolonged effect suggested that the lymphokine affected progenitor cells. In this study, we examined progenitor-derived colonies from the peripheral blood from this unusual X-CGD kindred. Progenitor-derived colonies examined before treatment were unable to generate superoxide as visualized by lack of nitro blue tetrazolium (NBT) reduction compared with normal controls. By contrast, colonies derived 7 days after a single INF-gamma injection were able to generate superoxide as shown by increased NBT reduction. Colonies harvested 21 days after treatment contained only rare cells capable of NBT reduction. Our results indicate that INF-gamma can reprogram the myeloid progenitor cells to express a partially corrected phenotype. This corrected phenotype is later expressed in daughter cells.

The effect of desferrithiocin, an oral iron chelator, on T-cell function

Desferrithiocin is a new, potent, orally available iron chelator. To determine whether this drug might be useful not only for iron-overload but also for immunosuppression, we studied the in vitro effects of desferrithiocin on T-lymphocyte function. Like deferoxamine, desferrithiocin inhibited, in a dose-dependent fashion, mitogen- and lectin-induced proliferation of both human and murine T cells. It was active at a concentration of 10 micrograms/mL. The inhibition of proliferation was reversed by ferrous chloride, but not by other metal salts, recombinant IL-2, or conditioned medium. Desferrithiocin also inhibited proliferation of constitutively dividing, and factor-independent EBV-transformed B cell and leukemic T-cell lines. Although desferrithiocin inhibited the induction of cytotoxic T lymphocyte (CTL) activity, it did not inhibit CTL- or natural killer-induced cytotoxicity. The agent did not inhibit the expression of activation antigens such as the IL-2 receptor on T cells, nor early measures of T-cell activation such as the influx of intracellular calcium. Thus, desferrithiocin, like deferoxamine, is a potent and reversible inhibitor of T-cell proliferation. This anti-proliferative effect inhibits T-cell function. Bioavailability after oral administration is a unique property of desferrithiocin, and would make it an attractive alternative to deferoxamine. Its immunomodulating properties may therefore be exploited in vivo to inhibit graft rejection or autoreactive T cells.

A phase I/II trial of recombinant granulocyte-macrophage colony-stimulating factor for children with aplastic anemia

Nine pediatric patients (median age, 8 years; range, 0.7 to 19 years), eight with refractory aplastic anemia and one with newly diagnosed aplasia, were enrolled in a phase I/II trial of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) administered via continuous intravenous infusion. Doses ranged from 8 to 32 micrograms/kg/d. Six of eight evaluable patients responded with a significant rise in neutrophil count (median fourfold increase; range, 2.5- to 31-fold) during the 28-day induction period. Five patients completed 2 further months of therapy (maintenance) with persistent or improved neutrophil responses. Three patients had bone marrow aspirates suggestive of increased erythropoiesis, although only one patient had improvement in peripheral hematocrit and platelet count. In the five patients completing maintenance, three experienced a rapid return to baseline counts after rhGM-CSF was discontinued, one maintained a neutrophil response for 2 months after drug discontinuation, and one has maintained a trilineage response for greater than 1 year off study. Drug therapy was well tolerated. Toxicity was minimal at doses from 8 to 16 micrograms/kg/d. Fever and rash were more commonly seen at 32 micrograms/kg/d. No patient developed an infection during the course of rhGM-CSF administration. These results demonstrate that rhGM-CSF increases peripheral neutrophil counts in children with refractory and newly diagnosed aplastic anemia and may be able to stimulate a multilineage response in a more limited number. Randomized, prospective trials are necessary to determine if rhGM-CSF administration will impact favorably on the morbidity and mortality of severe aplastic anemia.

Positive and negative elements regulate human interleukin 3 expression

The human interleukin 3 (IL-3) promoter is comprised of several cis-acting DNA sequences that modulate T-cell expression of IL-3. These are located within 315 nucleotides upstream of the mRNA start site. Transient expression of reporter genes linked to serially deleted sequences of the IL-3 promoter has allowed mapping of two activator sequences and an interposed repressor sequence. The proximal regulatory region is specific to IL-3 and prerequisite for efficient transcription. Its effect is enhanced by a second, more distal activating sequence consisting of an AP-1 binding site. Between the two activators lies a transcriptional silencer, which is a potent repressor in the absence of the AP-1 site. DNA-nuclear protein binding experiments demonstrate specific complex formation within each of these functional regions. Thus, both positive and negative regulatory elements appear to control expression of the human IL-3 gene in activated T cells.

Deficient T cell granulocyte-macrophage colony stimulating factor production in allogeneic bone marrow transplant recipients

The proliferation and differentiation of donor hematopoietic progenitor cells in bone marrow transplantation (BMT) recipients is influenced by hematopoietic growth factors, which could derive from either T cells or adherent stromal bone marrow cells, or both. In this study of 20 BMT recipients, we asked whether T lymphocytes arising from donor bone marrow grafts were able to express normal levels of granulocyte-macrophage colony stimulating factor (GM-CSF) mRNA, and to secrete normal levels of soluble GM-CSF in response to the mitogen phytohemagglutinin. We have found that T cells obtained up to 18 months following BMT express little or no PHA-induced GM-CSF message. T cell GM-CSF secretion in response to PHA is also reduced or absent. This T cell GM-CSF defect was observed in all patients studied, whether or not donor bone marrows had undergone T cell depletion. This defect likely reflects a broader deficit in mitogen-induced lymphokine production. This defect likely contributes to BMT recipients' blunted responses to infections, and contributes to graft failure in T cell-depleted transplants.

Hematopoiesis in vitro coexists with natural killer lymphocytes

The role of natural killer (NK) lymphocytes in the regulation of human hematopoiesis is controversial. NK-mediated inhibition of colony formation of hematopoietic progenitor cells has been irregularly reported for various cell lineages. In an effort to clarify such disparate findings, we studied the interaction of clearly defined NK and partially purified progenitor cell populations. Cell sorter purified CD16 positive blood NK cells and enriched autologous marrow progenitors were co-incubated at various lymphocyte to marrow cell ratios and then cultured in methylcellulose. There was no inhibition of myeloid, erythroid, or mixed colony formation. Similarly, activation of CD16 positive lymphocytes by interleukin-2 (IL-2) before co-incubation and co-culture did not result in inhibition of colony formation. Furthermore, in a newly designed assay system, we demonstrated that NK cells, which did not modulate colony-formation, remained capable of recognizing and killing rare K562 target cells seeded within the marrow cell population. Our results indicate that unstimulated and IL-2 activated isolated blood NK cells coexist with functioning autologous marrow progenitors in vitro.

Granulocyte-macrophage colony-stimulating factor and interleukin-3 mRNAs are produced by a small fraction of blood mononuclear cells

Northern blot analysis has identified granulocyte macrophage colony stimulating factor (GM-CSF) mRNA in monocytes and both GM-CSF and interleukin-3 (IL-3) mRNA in lymphocytes. However, these results have not addressed whether all cells or a subset of the population is capable of hematopoietic growth factor (HGF) production. To resolve this question, we applied in situ hybridization of radiolabeled antisense RNA probes to centrifuged preparations of total blood mononuclear cells (BMCs) and fractionated lymphocyte subpopulations. Without stimulation, no circulating cells expressed detectable levels of GM-CSF or IL-3 mRNA. On stimulation of BMCs with phorbol myristate acetate (PMA) and phytohemagglutinin or PMA and the calcium ionophore ionomycin, approximately 5% expressed GM-CSF mRNA and approximately 1% IL-3 mRNA. Control sense probes produced no labeled cells. To determine the subsets of lymphocytes capable of GM-CSF and IL-3 expression, BMCs were fractionated by FACS into CD8+ and CD4+ lymphocyte subsets and CD16+ (NK) cells. The unfractionated cells and cell fractions were then stimulated with PMA and ionomycin. Results demonstrated that 3% to 5% of the CD16+, CD8+, and CD4+ lymphocytes produced GM-CSF mRNA. However, the number of IL-3 mRNA-positive cells in the FACS-sorted subsets was greatly reduced (0.02% to 0.05%) as compared with the unseparated cells (1%). Treatment of BMCs with high-dose interleukin-2 (IL-2) for 1 week followed by PMA plus ionomycin resulted in a lymphocyte population in which 50% and 3% of cells expressed GM-CSF and IL-3 mRNA, respectively. Thus, GM-CSF and IL-3 mRNA expression in T cells and NK cells is restricted to a small fraction of cells that can be greatly expanded by IL-2 stimulation. These results suggest a possible physiologic mechanism for increasing HGF production by circulating lymphocytes.