Human IL-3 and GM-CSF act synergistically in stimulating hematopoiesis in primates

A human interleukin 3 analog with increased biological and binding activities

Human interleukin 3 (IL-3) variants generated by site-directed mutagenesis were analyzed in multiple biological and binding assays to identify residues critical for IL-3 activity. Two mutants carrying substitutions in the predicted hydrophilic region within the first alpha-helix, [Ala21,Leu22]IL-3 and [Ala21,Leu22,Ala25]IL-3 showed loss of biological activity and high-affinity binding. Mutants in a second predicted hydrophilic region, [Ala44,Leu45,Ala46]IL-3 and [Ala44,Ala46]IL-3, however, showed similar biological and binding activities to wild-type IL-3. Mutations in a C-terminal hydrophilic region that overlaps the fourth predicted alpha-helix led to either loss or gain of function. IL-3 analogs [Glu104,Asp105]-, [Leu108]-, [Asn108]-, [Thr108]-, and [Ala101,Leu108]IL-3 were less active than wild-type IL-3, whereas [Ala101]IL-3 and [Val116]IL-3 were 2- to 3-fold more potent. Significantly, the double mutant [Ala101,Val116]IL-3 exhibited a 15-fold greater potency than native IL-3. Receptor binding studies showed that [Ala101,Val116]IL-3 exhibited increased binding to the high- and low-affinity receptors of monocytes. These results show the generation of an IL-3 analog with increased biological and binding activities and support a model where the C terminus of IL-3 interacts with the alpha chain of the IL-3 receptor, making this region a useful focus for the development of more potent IL-3 agonists or antagonists.

Granulocyte-macrophage colony-stimulating factor. Preliminary observations on the influences of dose, schedule, and route of administration in patients receiving cyclophosphamide and carboplatin

BACKGROUND

In an attempt to learn how best to administer granulocyte-macrophage colony-stimulating factor (GMCSF), the authors performed a Phase I study of this agent. They were interested in the influences of dose, schedule, and route of administration on the effects of GMCSF in patients receiving standardized 1-day regimens of cyclophosphamide (CYCLO) and carboplatin (CBDCA).

METHODS

Between June 1988 and March 1991, 57 patients with advanced cancer received GMCSF in association with CYCLO 1 g/m2 plus CBDCA 225-700 mg/m2. After the first dose escalation to 300 mg/m2 of CBDCA, patients who had previously received chemotherapy or radiation therapy were excluded. GMCSF was administered in three different doses, five different schedules, and by two different routes. Altogether, 17 different treatment groups were observed. In addition, 24-hour GMCSF serum concentration curves were charted in four patients.

RESULTS

Using four sequential groups of three patients each who had received myelosuppressive treatment, treatment with CYCLO 1 g/m2 and CBDCA 225 mg/m2, the apparent superiority of daily subcutaneous injection over 30-minute daily IV infusion of GMCSF was demonstrated graphically. Subsequently, the authors observed apparent enhancement of GMCSF effects beyond those produced by the initially selected 20-day basic 10 micrograms/kg daily SC regimen beginning 2 days after chemotherapy. When administered SC every 12 hours for 14 days beginning the day after chemotherapy, GMCSF appeared to ameliorate the severity of both leukopenia and thrombocytopenia. These effects permitted escalation of the CBDCA dose to 700 mg/m2 (with 1 g/m2 of CYCLO) before cytotoxic tolerance limits were reached. Graphic small group comparisons suggest that GMCSF given SC in doses of 5 micrograms/kg twice daily may produce comparable leukocyte and platelet support after chemotherapy with lower toxicity than occurs from higher doses. Prechemotherapy priming with GMCSF twice daily for an additional 4 days (days -6 to -3) seems to ameliorate postchemotherapy cytopenias further but at the cose of some increased risk of GMCSF toxicity. Although most of the toxic effects of moderate-dose GMCSF are controlled by antihistamines and ibuprofen, oral glucocorticoids (e.g., prednisone, 10 mg twice daily during the second week of GMCSF administration) may be required in patients with serositis, pulmonary infiltrates, or severe skin eruptions.

CONCLUSIONS

Our observations suggest that GMCSF should be administered SC in doses of approximately 5 micrograms/kg every 12 hours for 10-14 days beginning the day after chemotherapy. Prechemotherapy priming with these same doses for four additional days (days -6 to -3) may additionally ameliorate postchemotherapy leukopenia and thrombocytopenia, but with increased risk of toxicity.

Amelioration of zidovudine-induced fetal toxicity in pregnant mice

The effects of zidovudine (AZT) on the fetus were investigated in pregnant mice by using parameters such as the number of fetuses, fetal size, and the fetal hepatic cell clonogenic assay. AZT caused dose-dependent toxicity to the fetus upon administration via drinking water to pregnant mice from days 1 to 13 of gestation. At the 0.5-mg/ml dose level, AZT caused a decrease in the number of fetuses to 12 from an average of 16.5 in control animals, and the fetal size (crown-rump length) was reduced from 10.5 to 8.5 mm. The CFU of the erythroid progenitor cell colonies derived from the fetal hepatic cells were decreased to 38% of that of the control, and the hematocrit dropped to 33.5 +/- 1.7 from a control value of 42.6 +/- 2.5. Concomitant administration of erythropoietin, vitamin E, or interleukin-3 to the AZT-treated pregnant mice caused a significant reversal in the AZT-induced toxicity to the fetus and to the mother's bone marrow. The success of therapeutic intervention was demonstrated by (i) restoration of the number of fetuses to the level of untreated controls, (ii) an increase in the size of fetuses to normal values, and (iii) an increase in hematocrit to > 40. The results suggest that AZT is toxic to the fetus in a dose-dependent manner and that treatment with erythropoietin, vitamin E, or interleukin-3 can ameliorate the AZT-induced fetal toxicity.

IL-3 stimulated haemopoietic stem cell proliferation: evidence for G protein independent mitogenic signalling events

Interleukin-3 stimulates the survival and proliferation of the FDCP-Mix 1 multipotent stem cell line. We have investigated the possible involvement of a guanyl nucleotide regulatory (G) protein(s) in the IL-3 stimulated proliferative response. We report here that pertussis toxin (PT) can partially inhibit IL-3 stimulated DNA synthesis and that this inhibition is bypassed by TPA. The ADP-ribosylation of the PT substrate G protein in vivo is complete in 2 hours without concomitant inhibition of IL-3 stimulated hexose transport or Na+/H+ exchange. When loaded into FDCP-Mix 1 cells fluoroaluminate and GTP-gamma-S, which can directly activate G proteins, are not capable of mimicking the effects of IL-3. Evidence is also presented that IL-3 does not stimulate a membrane-bound high affinity GTPase activity in the FDCP-Mix 1 cell line. These data suggest that a PT substrate G protein(s) can influence the IL-3 signalling cascade in an indirect or permissive manner, but that the IL-3 receptor does not directly couple to a PT substrate G protein.

Interleukin-3 induces antimicrobial activity against Leishmania amazonensis and Trypanosoma cruzi and tumoricidal activity in human peripheral blood-derived macrophages

The ability of interleukin-3 (IL-3) to induce antimicrobial and tumoricidal activity was evaluated. Macrophages infected with two intracellular protozoa, Leishmania amazonensis or Trypanosoma cruzi, were treated with cytokines. IL-3 induced a dose-dependent enhancement of microbistasis against leishmanias, and the activity of IL-3 (100 ng/ml) was comparable to that of gamma interferon (IFN-gamma) (1,000 U/ml). In addition, IL-3 in combination with either granulocyte-macrophage colony-stimulating factor (GM-CSF) or macrophage CSF (M-CSF) or with IFN-gamma reduced infection and lowered the required dose. IL-3 similarly activated macrophages to inhibit intracellular replication of T. cruzi. Furthermore, IL-3 induced antibody-independent tumoricidal activity against melanoma cells that was dose dependent and comparable to that of lipopolysaccharide and GM-CSF. The mechanisms by which IL-3 induced antimicrobial activity may involve at least the augmentation of oxidative capacity. IL-3, at concentrations of 0.5 ng/ml or greater, led to a significantly increased oxidative burst which paralleled the inhibition of protozoan replication. The enhancement of oxidative capacity by IL-3 (5 ng/ml or higher) was comparable to that of IFN-gamma. The induction of tumoricidal activity was associated with the production of tumor necrosis factor alpha (TNF-alpha), which in this system may feed back to enhance the macrophage inhibition of leishmanias, as demonstrated by neutralization of IL-3 activation by anti-TNF-alpha antibody. Thus, peripheral blood macrophages remain responsive to IL-3, as demonstrated by enhanced antimicrobial and tumoricidal activity. IL-3 may have potential clinical applications because of these properties and its effect on myelopoiesis.

The pathobiology of bronchial asthma

Early studies of patients dying from status asthmaticus revealed marked inflammation of the bronchial tree. Subsequent histological studies of the airways and examination of bronchoalveolar lavage fluid of subjects with mild asthma have confirmed the presence of airway inflammation in life. There is epithelial edema and desquamation, subepithelial deposition of collagen and fibronectin, and an inflammatory cell infiltrate in the mucosa. There are increased numbers of activated eosinophils, CD25-positive T lymphocytes, and immature macrophages with the phenotypic characteristics of blood monocytes. An increased expression of HLA class II is present on epithelium, macrophages, and other infiltrating cells. The severity of clinical asthma correlates with several measurements of the severity of the inflammatory response, suggesting a crucial role for airway inflammation in the pathophysiology of the disease. There is considerable interest and research into the mechanisms underlying the pathogenesis and maintenance of the inflammatory response in asthma. The development and maintenance of the inflammatory response in asthma is likely to be a consequence of a complicated interaction between various cells and the mediators they generate. The characterization of an ever-increasing number of cytokines is of particular interest. Interleukin-3, interleukin-5, and granulocyte-macrophage colony-stimulating factor are hematopoietic growth factors that increase the survival of eosinophils in culture and enhance certain eosinophil functions, such as mediator generation and toxicity. Alveolar macrophages derived from asthmatic subjects produce twofold to threefold more GM-CSF than do those from normal control subjects. Using in situ hybridization, the presence of IL-5 mRNA has been demonstrated in bronchial biopsies from asthmatic subjects. Thus IL-3, IL-5, and GM-CSF influence eosinophil function and survival, and may be generated by T lymphocytes and/or alveolar macrophages within the airways in asthma. In addition to these three cytokines, IL-4 and interferon-gamma may be crucial to the regulation of IgE biosynthesis. TNF-alpha and IL-1 are potentially important in the up-regulation of endothelial adhesion molecules. An important step in the recruitment of leukocytes to an inflammatory focus is margination to the vascular endothelium. Our understanding of the molecular events involved in migration of leukocytes to an inflammatory focus has been advanced by the discovery and characterization of a variety of cell adhesion molecules. The potential role of ELAM-1 and ICAM-1 in allergic inflammation is suggested by their up-regulation on vascular endothelium in association with late cutaneous responses to allergen and by their role in certain primate models of asthma.(ABSTRACT TRUNCATED AT 400 WORDS)

Interleukin-3 and granulocyte-macrophage colony-stimulating factor in combination: clinical implication

The multilineage hematopoietic effects of IL-3 appear to be most important for its clinical use comprising especially leucocyte and platelet responses. This was demonstrated to be dose dependent characterising doses of 250 to 500 micrograms/m2/day subcutaneously as hematopoietic effective and well tolerable. Since preclinical data suggest synergism between IL-3 and GM-CSF hematopoietic effects of their sequential administration were evaluated in 15 patients with preserved hematopoietic function. An enhanced stimulation of megakaryopoiesis combined with more pronounced stimulation of granulopoiesis than IL-3 alone could be demonstrated. The cytokine combination of IL-3 and GM-CSF was thus used during chemotherapy induced myelosuppression. Data indicates beyond the known amelioration of myelosuppression by GM-CSF additional chances to enhance platelet recovery which can be of important clinical impact.

Asthma: cells and cytokines

The pathology of bronchial asthma demonstrates a multicellular process. In an attempt to elucidate the cellular biology of airways inflammation, it becomes important to understand not only the biology of each individual cell type but also the interaction between different cells. This review focuses on a documentation of some of the biological effects of the constituent cells in the airway mucosa and a discussion of their potential interactions through the release and action of different cytokines. It seems likely that future research will address the in vivo release of different cytokine molecules in the asthmatic process using techniques of molecular biology. There likely will be increasing information available about the regulation and the actions of these molecules on target cells and tissues. Elucidation of some of the complex interactions between different cells and the role of different cytokine molecules may provide a novel approach to the therapy of bronchial asthma.

Clinical applications of human granulocyte-macrophage colony-stimulating factor

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a hematopoietic growth factor that stimulates myeloid cell proliferation and maturation and enhances the function of terminally differentiated effector cells. Phase I and II clinical trials have demonstrated mild to moderate toxicities at doses of less than 30 micrograms/kg/day. These studies suggest a potential role for this growth factor to stimulate myelopoiesis in patients with aplastic anemia, myelodysplastic syndromes, AIDS, chemotherapy-induced myelosuppression, chronic neutropenia, and following bone marrow transplantation. The potential clinical uses of GM-CSF will depend on results of studies designed to optimize its therapeutic efficacy.

Adjuvant therapy with recombinant interleukin-3 and granulocyte-macrophage colony-stimulating factor

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3) are important members of the system of hematopoietic growth factors which control blood formation. Recombinant human (rh) GM-CSF stimulates proliferation and differentiation of myeloid cells and enhances effectively the regeneration of granulocytes and monocytes after chemotherapy or bone marrow transplantation. RhIL-3 acts on multipotent progenitor cells and induces an increase of leukocytes, platelets and reticulocytes after in vivo application. Combination of rhIL-3 and rhGM-CSF exerts a highly synergistic action on several hematopoietic cell lineages in monkeys and patients. Sequential application of rhIL-3 (5 days) followed by rhGM-CSF (10 days) has equivalent effects on myelopoiesis and thrombopoiesis compared with the effects of 15 days' monotherapy with rhGM-CSF on myelopoiesis and of a 15 days' treatment with IL-3 on platelet production. This combination seems to be very potent to reduce risk of neutropenia-associated infection and thrombocytopenic bleeding in patients with hematopoietic failure.

Treatment of Diamond-Blackfan anaemia with haematopoietic growth factors, granulocyte-macrophage colony stimulating factor and interleukin 3: sustained remissions following IL-3

We have treated six transfusion-dependent, steroid-unresponsive, Diamond-Blackfan anaemia (DBA) patients with the recombinant human growth factors granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3), administered sequentially with an interim rest period. GM-CSF was given at a dose of 500 micrograms/m2/d subcutaneously for 6 weeks. Three patients increased their absolute reticulocyte counts 1.5-35-fold (mean 20.8-fold) and into the normal range, but only one showed a reduction in transfusion requirements. Between 4 and 25 weeks after discontinuation of GM-CSF, these six patients were treated with recombinant human IL-3, at doses of 60 or 125 micrograms/m2/d subcutaneously for 4-6 weeks. Three increased their absolute reticulocyte counts from 2- to 28-fold (mean 10.6-fold) and two required fewer transfusions. One of these two patients has remained transfusion independent for over a year since completion of IL-3 therapy, and the second patient required infrequent transfusions for 9 months and then became transfusion independent for the subsequent 5 months. The sustained clinical remissions seen in two of the six patients after IL-3 therapy is very encouraging and further studies in a larger cohort of DBA patients with IL-3 alone or in combination with GM-CSF or other growth factors should be carried out.

Combination of cytokines: current status and future prospects

Clinical trials with individual cytokines and extensive in vitro studies have provided the basis for the in vivo use of these molecules in combination. Animal models, with haemopoietic growth factors as well as preliminary studies in humans--as shown by our studies with the sequential use of IL-3 and GM-CSF in patients receiving intensive chemotherapy--indicate that the selection of the appropriate cytokines could optimize haematological responses according to particular clinical requirements. That immunotherapy with IL-2 can induce regression of disseminated human malignancies serves as an encouraging starting point for combinations with other cytokines with the goal of improving the therapeutic efficacy and reducing toxicity. Future prospects of combination therapy will be discussed.

The role of cytokines in oncology

The availability of sufficient quantities of recombinant human cytokines and promising preclinical data have led to their introduction into clinical trials. Cytokines have potential as new therapeutic agents in a variety of hematological disorders as well as in solid tumors. Only a few of the still increasing number of these glycoprotein hormones have been studied in humans so far, either as single agents or in combination with chemotherapy and other cytokines. Their clinical effects, beneficial role in supportive care, and use in the treatment of certain cancer patients are reviewed.

Enhanced hematopoietic activity of a human granulocyte/macrophage colony-stimulating factor-interleukin 3 fusion protein

Granulocyte/macrophage colony-stimulating factor-interleukin 3 (GM-CSF-IL-3) fusion proteins were generated by construction of a plasmid in which the coding regions of human GM-CSF and IL-3 cDNAs were connected by a synthetic linker sequence followed by subsequent expression in yeast. Both GM-CSF-IL-3 and IL-3-GM-CSF fusion proteins were purified to homogeneity and shown to bind to cell-surface receptors through either their GM-CSF or IL-3 domains. The fusion proteins exhibited enhanced receptor affinity, proliferative activity, and hematopoietic colony-stimulating activity compared with either IL-3 and/or GM-CSF alone. This suggests that GM-CSF-IL-3 fusion proteins may hold future promise as therapeutic agents.

Recombinant granulocyte-macrophage colony-stimulating factor after autologous bone marrow transplantation for lymphoid cancer

BACKGROUND

The period of neutropenia after autologous bone marrow transplantation results in substantial morbidity and mortality. The results of previous phase I-II clinical trials suggest that recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) may accelerate neutrophil recovery and thereby reduce complications in patients after autologous bone marrow transplantation.

METHODS

We conducted a randomized, double-blind, placebo-controlled trial at three institutions. The study design and treatment schedules were identical, and the results were pooled for analysis. One hundred twenty-eight patients were enrolled. Sixty-five patients received rhGM-CSF in a two-hour intravenous infusion daily for 21 days, starting within four hours of the marrow infusion, and 63 patients received placebo.

RESULTS

No toxic effects specifically ascribed to rhGM-CSF were observed. The patients given rhGM-CSF had a recovery of the neutrophil count to 500 x 10(6) per liter 7 days earlier than the patients who received placebo (19 vs. 26 days, P less than 0.001), had fewer infections, required 3 fewer days of antibiotic administration (24 vs. 27 days, P = 0.009), and required 6 fewer days of initial hospitalization (median, 27 vs. 33 days; P = 0.01). There was no difference in the survival rate at day 100.

CONCLUSIONS

In patients undergoing autologous bone marrow transplantation for lymphoid neoplasia, rhGM-CSF significantly lessens morbidity. Further studies will be required to establish its optimal dosage and schedule of administration.

Transfusion and the use of blood products

I have reviewed areas of development in the use of blood and blood products, placing emphasis on the complications of transfusion, particularly transmission of infection. Alloimmunization in relation to transfusion of red cells and platelets has been covered and suggestions for reducing this problem assessed. The potential methods of avoiding the infective complications have been discussed including the screening of blood for infective agents, the virucidal treatment of blood products during the manufacturing process and white cell depletion. The use of recombinant DNA technology to produce coagulation factors offers the possibility of further reducing infective risks. An area of clinical promise is the use of haematopoietic growth factors to treat bone marrow failure, either congenital or acquired, such as the myelosuppressive effects of cancer chemotherapy, and reduce reliance on blood products. The aim of the chapter is to encourage the rational use of a limited resource by considering the risks inherent in transfusion and alternative strategies. In doing this it is important to audit current and future practice, and it is suggested that reference is made to the suggestions of Hume (1989) for quality assessment and assurance in paediatric transfusion medicine.

The biology and clinical applications of granulocyte-macrophage colony-stimulating factor

GM-CSF is a hematopoietic growth factor that regulates myeloid cell proliferation and maturation and enhances the function of terminally differentiated effector cells. Results of clinical trials with GM-CSF in a number of disease states suggest a potential role of this growth factor to stimulate hematopoiesis. Future use of GM-CSF will depend on further studies to optimize its therapeutic efficacy.

Biochemical analysis of class I and class II MHC antigens in cynomolgus macaques by one-dimensional isoelectric focusing

To obtain a better estimate of major histocompatibility complex (MHC) polymorphism in the Old World macaque, Macaca fascicularis, class I and class II MHC proteins from 42 animals were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and one-dimensional isoelectric focusing (1D-IEF). The panel represented both related and unrelated animals with a total of at least 30 serologically distinct haplotypes. Cells were sequentially immunoprecipitated with monoclonal antibody (mAb) W6/32 for class I and with mAb L243 for class II molecules, followed by neuraminidase treatment. Both sets of immunoprecipitates yielded 5-7 major bands on IEF. All bands present in offspring were present in at least 1 parent. Siblings which were serologically identical for class I and which were non-stimulatory in mixed lymphocyte culture (MLC) yielded identical IEF patterns for both class I and class II; in other sibling pairs which were serologically identical for class I antigens (Ag), IEF produced convincing evidence that the siblings were indeed nonidentical, or helped to verify that recombination had occurred within the MHC. Specific bands were found which correlated with class I specificities A8, A24, and B25 previously defined by serology. Comparison of serological and biochemical data will broaden our understanding of the MHC in Macaca fascicularis and will increase the potential use of this species in transplantation research, as a model of disease, and for comparative studies.

Interleukin 2 infusion induces haemopoietic growth factors and modifies marrow regeneration after chemotherapy or autologous marrow transplantation

Administration of interleukin 2 (IL2) to patients with minimal residual malignant disease following myeloablative chemo-radiotherapy may augment immune reconstitution and reduce the risk of relapse by increasing cytotoxic effector function and cytokine dependent killing directed at residual malignant cells. The ability of IL2 generated activated killer cells to inhibit haemopoietic progenitor cells and to release gamma-interferon (gamma IFN) and tumour necrosis factor (TNF) may, however, retard haemopoietic recovery, as both TNF and gamma IFN inhibit normal myelopoiesis in vitro. To determine the effect of IL2 infusion on myeloid regeneration in vivo, we have examined haemopoietic recovery in patients receiving this cytokine following autologous marrow transplantation or ablative chemotherapy. We find that IL2 infusion accelerates neutrophil recovery and that granulocyte-macrophage colony stimulating factor (GMCSF) and IL3 mRNA become detectable in circulating mononuclear cells. Induction of TNF by IL2 may also contribute to subsequent acceleration of myelopoiesis by initiation of GM-CSF mRNA synthesis in patient marrow fibroblasts. These results show that IL2 infusion may facilitate myeloid recovery when administered during the period of haemopoietic regeneration following ablative chemoradiotherapy.

Hematopoietic colony-stimulating factors

In summary, hematopoietic growth factors have been discovered, biochemically characterized, cloned, produced by recombinant DNA technology, and put into clinical use in a period of 25 years. We are approaching a greater understanding of the cellular anatomy and molecular mechanisms that regulate production of the CSFs, the ways in which the CSFs interact with their cell surface receptors and trigger their biological effects, the nature of these receptors themselves and their mechanisms of signal transduction, and the effects of the CSFs in vitro and in vivo on hematopoietic progenitor cells and mature leukocytes. However, many questions remain. What is the mechanism that couples growth-factor binding to the triggering of cellular proliferation? How do multi-CSF and GM-CSF cross-compete at the level of the cell-surface receptor, and yet show no primary amino acid sequence homology? What are the mechanisms that regulate the tissue expression profile of multi-CSF compared to the genetically similar growth factor GM-CSF? And, what are the optimal dosages, schedules of administration, and combinations of CSFs optimal for each of several conditions of marrow failure? These are but a few of the questions that continue to occupy much current research interest.

Why clinicians should be interested in interleukin-3

Interleukin-3 (IL-3), a product of activated immune cells has recently been cloned and introduced in preclinical and clinical trials. The biological target-cell spectrum of IL-3 is broad and includes progenitor cells of various hematopoietic lineages as well as multiple stages of stem cell differentiation. IL-3 also induces growth of most primitive hemopoietic progenitors (CFU-blast). Synergistic effects on growth of myeloid cells (i.e. macrophages, eosinophils and blood basophils) are obtained by sequential use of IL-3 and later-acting myelopoietic cytokines. In addition, IL-3 supports terminal maturation, prolongs survival and enhances the functional properties of myeloid cells through high-affinity binding sites. In vivo administration of IL-3 is followed by an increase in peripheral white blood cell counts as well as by an increase in the number of circulating progenitor cells giving rise to mature hemopoietic cells in response to more lineage-restricted growth factors. IL-3 also regulates growth of leukemic cells and primes them to become more sensitive to cell cycle specific cytotoxic drugs. IL-3 apparently represents a novel and unique hemopoietic growth factor. Its clinical use should offer new strategies in the treatment of cytopenia, leukemic disease and in stem cell transplantation.

The inflammatory response in asthma exacerbation: changes in circulating eosinophils, basophils and their progenitors

Circulating eosinophils, basophils and eosinophil/basophil (Eo/B) progenitors were examined in 12 patients at the time of an exacerbation of asthma accompanied by sputum eosinophilia and after resolution of the exacerbation with inhaled corticosteroid treatment. Differential counts were performed and peripheral blood non-adherent mononuclear cells were cultured for 14 days in methyl-cellulose to determine the number of Eo/B and granulocyte-macrophage (GM) colonies without knowledge of the clinical conditions or findings. With resolution of the asthma exacerbation on beclomethasone therapy, there were significant falls in circulating eosinophils, basophils and Eo/B colonies whereas GM colonies were unchanged. To elucidate whether the observed changes could be due to systemic absorption or local action of inhaled corticosteroid, seven subjects with allergic rhinitis and no current evidence of lower airway inflammation (no symptoms of asthma and normal methacholine airway responsiveness) received 14 days' treatment with the same dose of inhaled beclomethasone or of placebo in a double-blind randomized cross-over study. No significant changes in airway function or in circulating cell counts were observed. The results suggest reduced production of eosinophils and basophils after the resolution of an exacerbation of asthma. This effect may be due to reduced levels of airway-derived eosinophil-basophil growth and differentiation factors.

Use of hematopoietic growth factors in radiation accidents

Molecularly cloned hematopoietic growth factors are likely to be useful in treating radiation victims with bone marrow suppression. Some effects, such as increased granulocytes, are clearly beneficial. Other effects, such as altering the probability of survival of hematopoietic stem cells, may also be important. Interesting questions remain to be studied including which molecularly cloned hematopoietic growth factor(s) to use, optimal dose, timing, combinations of growth factors, and other issues. Some can be studied in vitro or in animal models. Others require clinical trials. Molecularly cloned hematopoietic growth factors clearly herald a new era in treating radiation accidents.

Interleukin-3

Interleukin-3 (IL-3) is a hemopoietic growth factor involved in the survival, proliferation and differentiation of multipotent hemopoietic cells. In five mammalian species, including man, the gene encoding IL-3 has been isolated and expressed to yield the mature recombinant proteins. The human IL-3 gene encodes a protein of 133 amino acids with two conserved cysteine residues and 2 potential N-linked glycosylation sites; human native IL-3 has not been characterized. Comparison of the IL-3 genes revealed a more rapid evolutionary divergence than has been observed for other hemopoietic growth factors, and, hence, a more pronounced species specificity of the functional proteins was found. In agreement with its stimulatory action on immature multipotent cells, the in vivo actions of homologous recombinant IL-3 in nonhuman primates include a highly increased production of blood cells along the neutrophilic, eosinophilic and basophilic granulocyte as well as the monocyte, red cell and platelet lineages.

Hematopoietic growth factors: overview and clinical applications, Part I

The growth and differentiation of blood cells is regulated by a group of at least 12 glycoproteins, collectively known as hematopoietic growth factors. Advances in protein biochemistry and molecular genetics have provided the tools for the bulk production of these hormones for clinical application. Clinical trials of macrophage colony-stimulating factor, granulocyte macrophage colony-stimulating factor, granulocyte colony-stimulating factor, and interleukin-3 have all demonstrated significant effects on the peripheral blood counts of the recipients. The clinical usefulness of these agents in ameliorating post-chemotherapy myelosuppression, in the treatment of other cytopenias, and in enhancing engraftment after bone marrow transplantation has already been demonstrated. Potential applications to the therapy and diagnosis of other clinical disorders is under study. The history of the elucidation of these growth factors, our current understanding of their properties, interactions, and clinical effects, and the potential prospects for their future use in the manipulation of human blood cell production are the subject of this review.

Colony stimulating activity in the serum of patients with multiple myeloma is enhanced by interleukin 3: a possible role for interleukin 3 after high dose melphalan and autologous bone marrow transplantation for multiple myeloma

Sera from 36/37 multiple myeloma patients and 19/21 sera from patients with other solid or liquid tumours had granulocyte-macrophage colony stimulating activity (CSA) towards normal human donor bone marrow whereas 1/16 sera from normal donors had this activity. Unlike human rhGM-CSF and GM-CSF from 5637 (human bladder cell line) conditioned medium which is heat stable, CSA from serum is heat labile (56 degrees C/30 min). In multiple myeloma patients, CSA was detectable more than 2 years after treatment with 'high dose melphalan. Although multiple myeloma patients, at relapse, have sufficient CSA in their serum to produce maximal stimulation of GM-CFUc from normal donor bone marrow in vitro, their own GM population responds poorly. The results suggest that the failure of patients own bone marrow to respond to endogenous CSA may be due to damage to the stem cells of the marrow or the failure of precursor cells to respond to CSA. Addition of rhIL-3 to myelomatous serum increased the number of GM-CFUc from both normal and myelomatous bone marrow but did not stimulate the growth of MY-CFUc significantly. The results suggest that rhIL-3 may assist bone marrow recovery in multiple myeloma patients after intensive chemotherapy.