Chemical modification and site-directed mutagenesis of methionine residues in recombinant human granulocyte colony-stimulating factor: effect on stability and biological activity

Chemical modification and mutagenesis of methionines in recombinant human granulocyte colony-stimulating factor (G-CSF) were investigated. Selective oxidation of G-CSF by H2O2 and t-butyl hydroperoxide leads to generation of different oxidized forms. Four modified forms were isolated and shown to contain 1 to 4 oxidized methionyl residues. All methionines in G-CSF are reactive, with reaction kinetics following the order of Met1>Met138>Met127>>>Met122. H2O2 oxidation of Met122 is relatively slow and is biphasic with a faster second reaction phase being affected by the oxidation of Met127. All oxidized forms retain gross G-CSF conformation similar to that of the native molecule and are able to bind the soluble G-CSF receptor. However, G-CSF form oxidized at both Met127 and Met122 is unstable and exhibits decreased ability to dimerize the receptor after exposure to acid or elevated temperature. All modified forms, except Met1-oxidized G-CSF, also show significantly lower biological activity. Our data suggest that Met138 is solvent accessible and its surrounding microenvironment may be critical for G-CSF function, whereas Met127 is less accessible to solvent and Met122 is near the hydrophobic core. Oxidation at both Met127 and Met122 results in alterations of G-CSF structure that affect the apparent molecular size, polarity, and stability and lead to the loss of G-CSF biological function. G-CSF variants with Leu replacement at Met127 or at Met138 are not completely resistant to oxidation-induced inactivation, while the variant with Leu replacement at both sites is more stable and can retain in vitro biological activity following oxidation.

The majority of stem cell factor exists as monomer under physiological conditions. Implications for dimerization mediating biological activity

Soluble Escherichia coli-derived recombinant human stem cell factor (rhSCF) forms a non-covalently associated dimer. We have determined a dimer association constant (Ka) of 2-4 x 10(8) M-1, using sedimentation equilibrium and size exclusion chromatography. SCF has been shown previously to be present at concentrations of approximately 3.3 ng/ml in human serum. Based on the dimerization Ka, greater than 90% of the circulating SCF would be in the monomeric form. When 125I-rhSCF was added to human serum and the serum analyzed by size exclusion chromatography, 72-49% of rhSCF was monomer when the total SCF concentration was in the range of 10-100 ng/ml, consistent with the Ka determination. Three SCF variants, SCF(F63C), SCF (V49L,F63L), and SCF(A165C), were recombinantly expressed in Escherichia coli, purified, and characterized. The dimer Ka values, biophysical properties, and biological activities of these variants were studied. Dimerization-defective variants SCF(F63C)S-CH2CONH2 and SCF(V49L,F63L) showed substantially reduced mitogenic activity, while the activity of the Cys165-Cys165 disulfide-linked SCF(A165C) dimer was 10-fold higher than that of wild type rhSCF. The results suggest a correlation between dimerization affinity and biological activity, consistent with a model in which SCF dimerization mediates dimerization of its receptor, Kit, and subsequent signal transduction.

Epitope mapping and immunoneutralization of recombinant human stem-cell factor

The epitope regions of three anti-[stem-cell factor (SCF)]g have been mapped by characterization of immunoreactivities against truncated forms of SCF in immunoblots and against synthetic peptides in solution-phase competition ELISA. Two of the antibodies, mAb 7H6 and mAb 8H7A, were raised against Escherichia coli-derived human SCF-(1-164) while the third, polyclonal antibody (pAb) 1337, was raised against a peptide corresponding to residues 3-31 of human SCF. The epitopes of mAbs 7H6 and 8H7A have been mapped to residues 61-95 and 95-110, respectively. The epitope of pAb 1337 has been mapped to residues 21-31. The ability of the anti-SCF Ig to recognize E. coli-derived human SCF presented in various formats, i.e. partially denatured (fixed in standard ELISA or on a western blot) or native (in solution), was studied, mAb 7H6 recognized its epitope in partially denatured or native SCF with equally high affinity, while mAb 8H7A and pAb 1337 recognized their epitopes only when SCF was at least partially denatured, mAb 7H6 was found to neutralize in vitro SCF-mediated cell proliferation and SCF binding to its receptor, when present in equimolar concentrations relative to the ligand, suggesting that the epitope region is functionally significant. Evidence that the mAb 7H6 epitope is represented by discontinuous regions (residues within sequences 61-65 and 91-95 are critically involved) is presented. The observation that the mAb 7H6 epitope is discontinuous has implications for the structure of SCF.

Expression patterns of immediate early transcription factors in human non-small cell lung cancer. The Lung Cancer Study Group

In 1995, there will be 172,000 new cases of lung cancer diagnosed and 153,000 deaths from this disease in the United States. While the pathogenesis of the disease process is poorly understood, a growing body of evidence suggests that abnormalities in cellular regulatory genes may play an important role in the induction, maintenance and/or progression of some tumor types. These genes include both growth promoting oncogenes as well as growth inhibitory or suppressor genes. Included among these genetic sequences are several cellular transcription factors. A group of these factors including c-jun, c-fos and EGR1 are members of a class of genes known as immediate early genes whose expression are inducible by a variety of stimuli including mitogenic and differentiation inducing growth factors, indicating a potential important role for these genes in normal growth processes. Since these genes are involved in early regulation of cellular growth properties and at least two (c-jun and c-fos) can act as oncogenes, we wished to determine whether their expression levels were altered in human non-small cell lung cancers (NSCLC) compared to normal lung tissue. To address this, Northern blot analyses were performed using c-fos, c-jun and EGR1 probes on RNA extracted from 101 NSCLC tumor specimens and adjacent uninvolved lung tissue. Analysis of this cohort revealed that 72% of the normal tissues demonstrate significantly greater expression of these transcription factors as compared to adjacent malignant tissue. Moreover, this expression pattern appeared to be coordinate for all three genes in the majority of cases. This differential expression pattern was confirmed at the protein level using an immunohistochemical approach with antibodies directed against the c-jun, c-fos and EGR1 gene products. Southern blot analyses demonstrated no gross alterations of these sequences at the DNA level, indicating that the observed differential expression pattern was not due to gross structural changes in the genes. These data suggest that down-regulation of these genes may be involved in the pathogenesis of lung cancer.

Antibodies to canine granulocyte colony-stimulating factor induce persistent neutropenia

A severe persistent neutropenia developed in a rabbit that was injected intradermally with 120, 60, 60, and 120 micrograms of recombinant canine granulocyte colony-stimulating factor (cG-CSF) on days 1, 22, 31, and 44, respectively. The neutropenia was present from day 44 to day 205. The nadir of the neutropenia (60 cells/microliters) occurred in conjunction with peak antibody titer (640,000) to cG-CSF on day 58. The immune antiserum from this rabbit reacted positively for cG-CSF on Western blot analysis. The immune antiserum also neutralized the activity of cG-CSF. On day 160, examination of the bone marrow showed marked granulocytic hypoplasia and mild erythroid hyperplasia. On day 205, the rabbit was still neutropenic (430 cells/microliters), even though the last injection of cG-CSF was given 161 previously. Necropsy on day 205 showed that there was still mild granulocytic hypoplasia with mild erythroid hyperplasia. Because of the lack of any inflammatory foci found at necropsy and the granulocytic hypoplasia, it was thought that the neutropenia was most likely due to decreased production and was not a consumptive process. It is hypothesized that the antibody that was produced to cG-CSF neutralized the effect of endogenous rabbit granulocyte colony-stimulating factor and prevented the normal proliferation and maturation of the rabbit neutrophils.

High level expression of human leukemia inhibitory factor (LIF) from a synthetic gene in Escherichia coli and the physical and biological characterization of the protein

LIF is a multi-functional cytokine that elicits effects on a broad range of cell types. In this report, we present the high level expression of human LIF (hLIF) from a chemically synthesized gene template in Escherichia coli where it comprises up to 25% of the cellular protein. The recombinant hLIF, after purification and folding, was examined using CD, FTIR spectroscopy and light scattering. CD and FTIR spectra showed that the hLIF is an alpha-helical protein and has a distinct tertiary structure. The IFTR spectrum resembles that of other four helical bundle proteins including G-CSF and IL-6. Light scattering analysis indicated that it is a monomeric protein, distinguishing it from M-CSF and interferon gamma, which also belong to the class of four helical bundle proteins but are dimeric. Recombinant hLIF was assayed for its activity on the murine leukemic cell line, M-1 as well as on human leukemic cell line, ML-1. It inhibited the growth of M-1 cells and differentiated them towards macrophages. However, it did not have any differentiation inducing effect on human leukemic cell lines alone or in combination with other cytokines.

Cysteine 17 of recombinant human granulocyte-colony stimulating factor is partially solvent-exposed

Oh-eda et al. have shown instability of granulocyte-colony stimulating factor (G-CSF) upon storage above pH 7.0 [J. Biol. Chem. (1990) 265, 11,432-11,435]. To clarify the mechanism of this instability, the accessibility of a free cysteinyl residue at position 17 for disulfide exchange reaction was examined using a sulfhydryl reagent. The results show that the cysteine is partially solvent-exposed in both glycosylated and nonglycosylated forms, suggesting that the exposure of the cysteine plays a critical role in the instability of the protein. This is supported by the facts that at low pH where the cysteine is protonated, both proteins have much greater stability and that a Cys17-->Ser analog is extremely stable at neutral pH and 37 degrees C. It was observed that the rate of sulfhydryl titration is slower for the glycosylated form than for the nonglycosylated form, suggesting that the cysteine residue is less solvent-exposed for the former protein or that the pKa is somewhat more basic. In either case, the carbohydrate appears to affect the reactivity of the sulfhydryl group through steric hindrance or alteration in local conformation. Both the glycosylated and nonglycosylated proteins showed essentially identical conformation as determined by circular dichroism, fluorescence, and infrared spectroscopy. Unfolding of these two proteins, induced either by guanidine hydrochloride or by pH, showed an identical course, indicating comparable conformational stability. Contribution of conformational changes to the observed instability at higher pH is unlikely, since little difference in fluorescence spectrum occurs between pH 6.0 and 8.0.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased granulopoiesis after sequential administration of transforming growth factor-beta 1 and granulocyte-macrophage colony-stimulating factor

Transforming growth factor-beta 1 (TGF-beta 1) is an inhibitor of the growth and differentiation of immature hematopoietic progenitors in vitro; however, we have demonstrated that TGF-beta 1 can promote granulopoiesis in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) in vitro. We therefore examined the effect of the combined administration of TGF-beta 1 and GM-CSF in vivo. First, TGF-beta 1 enhanced the specific binding of GM-CSF (2.0-fold) on bone marrow cells, reaching a maximum 40 hours after injection, while the specific binding of interleukin-3 (IL-3) was unaffected. Using GM-CSF-specific binding to determine the optimal regimen for cytokine administration in vivo, we found that the administration of TGF-beta 1 and GM-CSF in sequence increased myelopoiesis. Total numbers of colony-forming units-granulocyte/macrophage (CFU-GM) and myeloblasts per femur were increased above the level obtained with the simultaneous injection of TGF-beta 1 plus GM-CSF, GM-CSF alone or TGF-beta 1 alone. Further, the sequential administration of TGF-beta 1 and GM-CSF resulted in enhanced numbers of mature granulocytes in both the bone marrow and peripheral blood. In contrast, the sequential combination of TGF-beta 1 and GM-CSF did not enhance the numbers or increase the recovery of erythroid cells in the bone marrow. These results show that TGF-beta 1 in vivo as in vitro has a multifunctional effect on bone marrow progenitors, and by using an optimal combination of TGF-beta 1 and GM-CSF in vivo, one can selectively increase both the central and peripheral granulopoietic compartments.

Glycosidase digestion, electrophoresis and chromatographic analysis of recombinant human granulocyte colony-stimulating factor glycoforms produced in Chinese hamster ovary cells

Recombinant human granulocyte colony stimulating factor (G-CSF) produced in Chinese hamster ovary cells is glycosylated. The carbohydrate compositional analysis indicated that G-CSF molecule contains sialic acid, galactose and galactosamine. By isolation and characterization of the purified glycopeptides obtained from cleavages by Staphylococcal aureus V-8 protease and cyanogen bromide, the O-linked glycosylation site was confirmed to be a Thr residue at position 133. Neuraminidase and O-glycanase digestion followed by sodium dodecyl sulfate polyacrylamide and isoelectric focusing gel electrophoreses distinguished two possible carbohydrate structures attached at Thr-133: structure A, NeuNAc-Gal-beta(1,3)-GalNAc-O-Thr; and structure B, NeuNAc-Gal-beta(1,3)-[NeuNAc]-GalNAc-O-Thr. Different glycoforms, undigested or after glycosidase digestion, can also be separated by ion-exchange or reversed-phase high-performance liquid chromatography. The approach described in this report provides a simple and valuable procedure to characterize glycoprotein structures containing simple carbohydrate moieties.

Characterization of inclusion bodies in recombinant Escherichia coli producing high levels of porcine somatotropin

The protein composition of inclusion bodies (IBs) formed in recombinant Escherichia coli producing high levels of porcine somatotropin (pST) was analyzed by one- and two-dimensional protein gel electrophoresis. Recombinant pST is exclusively recovered from the insoluble cell fraction. Results indicate that, in addition to the main species of pST, subspecies with different isoelectric points and degradative fragments are contained within IBs. The presence of outer membrane proteins in IB fractions results from coprecipitation of cell debris during IB preparation and not from specific in vivo or in vitro interaction of these proteins with IBs. Cells producing pST contain up to three IBs located in the cytoplasm. The implication of high level gene expression on the uniformity of the desired product is discussed.

Comparative analysis of the effects of recombinant cytokines on the growth and differentiation of ML-1, a human myelogenous leukemic cell line

We have investigated the effect of a number of cytokines on the human acute myelomonocytic leukemic cell line, ML-1. The differentiation inducing effects of interleukins (IL-1 beta, IL-3 and IL-6), colony stimulating factors (GCSF and GMCSF), TNF, LIF and IFNg, were studied either individually or in combination. Criteria for monocytic differentiation were as follows: an increase in the percentage of cells reducing nitroblue tetrazolium (NBT) salt, an increase in the alkaline phosphatase activity as well as the appearance of macrophagic phenotype. Among all the cytokines tested, only TNF was found to induce differentiation and to inhibit growth of ML-1 cells. IL-3, IL-6, interferon gamma, GCSF and to a smaller extent IL-1 beta and GMCSF synergized the differentiation inducing activity of TNF.

Effect of recombinant canine granulocyte colony-stimulating factor on peripheral blood neutrophil counts in normal cats

Recombinant canine granulocyte colony-stimulating factor (rcG-CSF) was administered subcutaneously at a dosage of 5 micrograms/kg/day to five healthy, young adult cats for 42 days. Mean neutrophil counts +/- standard deviation increased significantly (P < 0.001) from 10,966/microL +/- 2324 to 30,688/microL +/- 5296 within 24 hours after administration of the first dosage of rcG-CSF. Mean neutrophil counts reached 52,978/microL +/- 11,207 on day 6, representing a second significant increase (P < 0.01) over the previous 5 days. Mean neutrophil counts continued to increase, reaching 66,994/microL +/- 12,419 on day 14, then remaining within a range of 66,994 to 87,839/microL throughout the remainder of the study. The maximum mean neutrophil count was 87,839/microL +/- 8,695 on day 42. Neutrophil counts remained high until the administration of recombinant canine granulocyte colony-stimulating factor was discontinued 42 days after initiation of therapy. Once the rcG-CSF administration was discontinued, neutrophil counts returned to pretreatment values within 5 days. There were no significant changes in numbers of any of the other cell lines. There was no clinically significant toxicosis associated with the administration of rcG-CSF.

Neutrophil function in normal and Chediak-Higashi syndrome cats following administration of recombinant canine granulocyte colony-stimulating factor

The effects of recombinant canine granulocyte colony-stimulating factor (rcG-CSF) on leukocyte counts and neutrophil function in clinically normal cats and in cats heterozygotic and homozygotic for Chediak-Higashi syndrome (CHS) were examined. CHS is a genetic disease characterized by neutropenic episodes and defects in a variety of phagocyte functions. Short-term administration of rcG-CSF at 10 micrograms/kg body weight resulted in a five- to tenfold increase in circulating granulocytes by day 10 of administration and normalizes CHS neutrophil counts by day 3. The drug was specific for neutrophils as determined by differential cell counts. Neutrophil chemotaxis under agarose and phagocytosis of Escherichia coli were characterized following administration of rcG-CSF in vivo. Granulocytes elicited by rcG-CSF show enhanced chemotactic abilities toward activated serum, increased spontaneous migration, and an enhanced ability to ingest opsonized E. coli. At a concentration of 1 nM rcG-CSF in vitro, chemotaxis and spontaneous migration were increased, with no effect on phagocytosis. CHS neutrophil function was improved by administration of rcG-CSF in all parameters studied, although the defect in chemotaxis was present throughout the treatment period. We conclude from this study that neutrophils elicited by rcG-CSF are functionally enhanced and that rcG-CSF may be a viable therapy for CHS and other related disorders.

Effects of recombinant canine granulocyte colony-stimulating factor on white blood cell production in clinically normal and neutropenic dogs

Recombinant canine granulocyte colony-stimulating factor (rcG-CSF) was administered to clinically normal dogs, cyclic-hematopoietic dogs, and dogs undergoing autologous bone marrow transplantation, to determine whether rcG-CSF could be used to stimulate WBC production and function in normal and neutropenic dogs. To the normal dogs, rcG-CSF was administered by SC injection at rates of 1 microgram/kg of body weight, q 12 h; 2 micrograms/kg, q 12 h; or 5 micrograms/kg, q 12 h. A significant dose-dependent increase in the WBC count resulted from the stimulation of bone marrow progenitor cells. The increased WBC count was characterized by mature neutrophilia and monocytosis. Neutrophil myeloperoxidase and phagocytic activity were normal in rcG-CSF-treated normal dogs, demonstrating the production of normal functional neutrophils in response to rcG-CSF treatment. Recombinant canine G-CSF prevented neutropenia and associated clinical signs but did not completely eliminate the cycling of neutrophils in cyclic-hematopoietic dogs when it was administered at rates of 1 microgram/kg, q 12 h, and 2.5 micrograms/kg, q 12 h. The time to bone marrow reconstitution was not decreased in dogs treated with rcG-CSF at a rate of 2.5 micrograms/kg, q 12 h, for 13 days following autologous bone marrow transplantation. On the basis of our findings, we suggest that treatment with rcG-CSF is an effective way to stimulate myelopoiesis in dogs, but that the dose of rcG-CSF required to stimulate WBC production will vary depending on the cause of neutropenia. Recombinant canine G-CSF should be useful in stimulating production and maintaining function of WBC for treatment of clinical diseases seen commonly in veterinary practice.

Folding and oxidation of recombinant human granulocyte colony stimulating factor produced in Escherichia coli. Characterization of the disulfide-reduced intermediates and cysteine----serine analogs

The folding and oxidation of recombinant human granulocyte colony-stimulating factor solubilized from Escherichia coli inclusion bodies was investigated. During the folding process, two intermediates, I1 and I2, were detected by kinetic studies using high performance liquid chromatography. I1 exists transiently and disappears quickly with the concomitant formation of I2. In contrast, I2 requires a longer time to fold into the final oxidized form, N. CuSO4 catalysis increases the folding rate of I2 from I1, while CuSO4 and elevated temperature (37 degrees C) have a dramatic effect on the folding rate of N from I2. These observations suggest the following sequential oxidative folding pathway. [sequence: see text] Peptide map analysis of the iodoacetate-labeled intermediates revealed that I1 represents the fully reduced granulocyte colony-stimulating factor containing 5 free cysteines; I2 is the partially oxidized species containing a single Cys36-Cys42 disulfide bond; and N, the final folded form, has two disulfide bonds. The physicochemical properties and biological activities of I1, I2, N, and several Cys----Ser analogs made by site-directed mutagenesis were further investigated. In guanidine hydrochloride-induced denaturation studies, the disulfide-reduced intermediates and the analogs missing either of the disulfide bonds are conformationally less stable than those of the wild type molecule or the analog with the free Cys at position 17 changed to Ser. Recombinant human granulocyte colony stimulating factor lacking either disulfide bond or both has overall secondary and tertiary structures different from those of the wild type molecule and exhibits lower biological activity. These studies show that disulfide bond formation is crucial for maintaining the molecule in a properly folded and biologically active form.

Detection and quantitation of recombinant granulocyte colony-stimulating factor charge isoforms: comparative analysis by cationic-exchange chromatography, isoelectric focusing gel electrophoresis, and peptide mapping

Routine quantitation of recombinant human granulocyte colony-stimulating factor charge isoforms in the purified protein product requires development of a reliable analytical method. In this report, isoelectric focusing gel electrophoresis, peptide mapping, and cation-exchange high-performance liquid chromatography are compared and evaluated in the analysis of charge isomers that may be present in the recombinant factor. Due to a lack of sensitivity and reliability, isoelectric focusing gel electrophoresis and peptide mapping are not recommended. However, peptide mapping can distinguish aberrant peptides with differences in charges and provide separation for subsequent structural characterization. By this approach, an N-terminally blocked formylmethionyl species was identified to be the minor charge isoform in the purified preparations of recombinant human granulocyte colony-stimulating factor. In contrast to electrophoresis and peptide mapping, a strong cationic-exchange chromatographic procedure was found to be the most selective, sensitive, and reproducible analytical method. The sensitivity and reliability of the method were evaluated and validated using the formylmethionyl isoform and several deamidated analogs (Gln----Glu) made by site-directed mutagenesis. Recombinant human granulocyte colony-stimulating factor preparations contain a very low to undetectable level of the formylmethionine isoform and have no detectable deamidated isoforms.

Inhibition of invasion and metastasis in cells transfected with an inhibitor of metalloproteinases

The balance between levels of metalloproteinases and their corresponding inhibitors is a critical factor in tumor invasion and metastasis. Down-regulation of the activity of these proteases was achieved by transfection of invasive and metastatic rat cells with the complementary DNA for metalloproteinase inhibitor/tissue inhibitor of metalloproteinase 2 (MI/TIMP-2), a novel inhibitor of metalloproteinases recently described. (Y. A. DeClerck et al., J. Biol. Chem., 264: 17445-17453, 1989; W. G. Stetler-Stevenson et al., J. Biol. Chem., 264: 17374-17378, 1989). Secretion of functional MI/TIMP-2 protein in stably transfected cells resulted in a marked decrease in metalloproteinase activity. Partial suppression of the formation of lung colonies after i.v. injection in nude mice was observed in a transfected clone expressing high levels of MI/TIMP-2. Production of MI/TIMP-2 in four clones markedly reduced tumor growth rate in vivo after s.c. injection and completely suppressed local tissue invasion. Thus, down-regulation of metalloproteinase activity has a striking effect on local invasion and partially suppresses hematogenous metastasis.

Use of Recombinant Canine Granulocyte Colony-Stimulating Factor to Decrease Myelosuppression Associated with the Administration of Mitoxantrone in the Dog

Ten dogs were given mitoxantrone at a dose of 5 mg/m2 body surface area intravenously. Recombinant canine granulocyte colony-stimulating factor (rcG-CSF) was administered subcutaneously daily for 20 days after an infusion of mitoxantrone in five of these dogs to determine the effect of the hematopoietic growth factor on the duration and severity of myelosuppression. The median neutrophil counts dropped below normal (less than 3,000/uL) for 2 days in the dogs that received rcG-CSF, and for 5 days in the dogs that received only mitoxantrone. Four of five dogs not treated with rcG-CSF and none of those receiving rcG-CSF developed serious neutropenia (less than 1,500/uL). The neutrophil counts were significantly (P less than 0.05) higher in the rcG-CSF treated dogs at all time points except before the administration of the colony-stimulating factor, and the sixth day after the mitoxantrone was administered. These findings demonstrate that rcG-CSF is capable of reducing the duration and severity of mitoxantrone-induced myelosuppression.

Granulocyte colony-stimulating factor effects on lymphocytes and immunoglobulin concentrations in periparturient cows

Immunomodulatory effects of recombinant bovine granulocyte colony-stimulating factor were evaluated in periparturient dairy cows. Eleven of 21 cows were experimentally infected with Staphylococcus aureus in one mammary quarter prior to the study. Cows were assigned to four groups in a randomized complete block design to evaluate the effects of recombinant bovine granulocyte colony-stimulating factor (5 micrograms/kg of body weight or placebo injected subcutaneously once daily beginning 14 d prepartum through 10 d postpartum) on infected and uninfected cows during the periparturient period. Blood lymphocytes were isolated and evaluated from 5 wk before expected parturition through 7 wk postpartum. Lymphocyte function was evaluated using a blastogenesis assay, a mitochondrial methylthiazoltetrazolium cleavage activity assay, and an in vitro assay of IgM production. Serum concentrations of IgM, IgG1, conglutinin, and hemolytic complement were also determined. Injections of cows with recombinant bovine granulocyte colony-stimulating factor resulted in enhanced lymphocyte blastogenesis and mitochondrial methylthiazoltetrazolium cleavage activity in unstimulated cultures, higher serum IgM, and increased in vitro IgM production by B lymphocytes. These data provide support for the use of recombinant bovine granulocyte colony-stimulating factor to alleviate immunosuppression in periparturient cows.

Effect of recombinant human granulocyte colony-stimulating factor on hematopoiesis in normal cats

The objective of this study was to determine how recombinant human granulocyte colony-stimulating factor (rhG-CSF) affects hematopoiesis in normal cats. Recombinant human G-CSF was given at 3.0, 5.0, and 10.0 micrograms/kg to two cats each s.c. twice daily for 21 days. This resulted in significant (p less than 0.01) elevations of peripheral blood neutrophils from 3.0- to 9.2-fold above pretreatment levels and significantly (p less than 0.02) above levels of nontreated control cats (n = 4). A statistically significant dose-related response was not seen at these dosages in any parameter evaluated. The period of maximum neutrophilia occurred between days 10 and 14 of rhG-CSF treatment, with maximum neutrophil counts ranging from 20,370 cells/microliters to 61,400 cells/microliters (normal is less than 12,500). Lymphocytosis (greater than 7000 lymphocytes/microliters) and monocytosis (greater than 850 monocytes/microliters) were observed in 50% of the cats receiving rhG-CSF during the period of maximal neutrophil stimulation. Monocyte counts in treated cats were significantly (p less than 0.01) elevated over those of treatment controls on days 12-17. Lymphocyte numbers in rhG-CSF-treated cats were significantly elevated (p less than 0.05) over pretreatment controls on days 12 and 14 of rhG-CSF treatment. No significant changes were observed in reticulocyte counts, platelet counts, or hematocrit levels. By day 19, neutrophil levels had dropped significantly (p less than 0.01) from the maximum neutrophil levels, with one cat attaining a normal blood neutrophil count by day 21 of rhG-CSF treatment. Marrow aspirates revealed an overall increase in marrow cellularity through day 14 of treatment in rhG-CSF-treated cats, with increased myeloid:erythroid ratios (two- to ninefold) over those of nontreated controls. The erythroid and lymphoid component of the marrow decreased from day 0 to day 14, whereas the early myeloid progenitors (myeloblasts, progranulocytes, and myelocytes) increased significantly (p less than 0.05). No significant differences in the percentage of later myeloid forms in the marrow were observed over the treatment period. In vitro colony-forming assays of marrow obtained from treated cats revealed increases in granulocyte-macrophage colony-forming units (CFU-GM) through day 14, with subsequent decreases by day 21 of rhG-CSF treatment. Recombinant human G-CSF was also effective at in vitro stimulation of feline marrow cells from untreated cats in a dilution study, with maximal CFU-GM formation at 0.1 microgram rhG-CSF/ml assay.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of granulocyte colony-stimulating factor administration to periparturient cows on neutrophils and bacterial shedding

Administration of recombinant bovine granulocyte colony stimulatory factor to periparturient dairy cows was evaluated as a method to prevent periparturient immunosuppression. Eleven of 21 cows were experimentally infected with Staphylococcus aureus in one mammary quarter prior to the study. Cows were randomly assigned to four groups in a 2 x 2 factorial design to evaluate the effects of placebo or recombinant bovine granulocyte colony stimulatory factor administration on chronic, subclinically infected and uninfected cows during the periparturient period. Blood neutrophils were isolated and evaluated for phagocytic activities 5 wk before expected parturition through 7 wk postpartum. Administration of recombinant bovine granulocyte colony stimulatory factor (5 micrograms/kg body weight or placebo subcutaneously beginning 14 d prepartum through 10 d post-partum) resulted in a prepartum and postpartum leukocytosis of 35,600/microliters and 53,500/microliters, respectively. This was attributed to a mature neutrophilia of 24,010/microliters during prepartum and 38,080/microliters during postpartum treatment periods (pretreatment baseline = 2330/microliters). Mononuclear cell counts averaged 7610/microliters during prepartum and 9830/microliters during postpartum treatment periods (baseline = 3450/microliters). Neutrophil random and directed migration were reduced during recombinant bovine granulocyte colony stimulatory factor treatment compared with placebo or baseline levels. Ingestion of bacteria and cytotoxicity by neutrophils was increased during recombinant bovine granulocyte colony stimulatory factor therapy compared with placebo or baseline levels. Shedding of S. aureus in lacteal secretions was unaffected by recombinant bovine granulocyte colony stimulatory factor treatment. In summary, administration of recombinant bovine granulocyte colony stimulatory factor increased the number and functional activity of neutrophils and prevented some aspects of periparturient immunosuppression in dairy cows.

Transforming growth factor-beta trans-modulates the expression of colony stimulating factor receptors on murine hematopoietic progenitor cell lines

Transforming growth factor beta (TGF-beta) is a potent and selective growth inhibitor of early hematopoietic progenitors and leukemic cells. The cellular mechanism(s) underlying this antiproliferative effect is, however, currently unknown. In the present study, we demonstrate that TGF-beta inhibits the expression of granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin 3 (IL-3), and granulocyte-CSF (G-CSF) receptors on murine factor-dependent and independent hematopoietic progenitor cell lines without a significant change in receptor affinity. A maximum reduction in GM-CSF receptor numbers of 65% to 77% was observed by 96-hour incubation with TGF-beta. The TGF-beta induced trans-down-modulation of GM-CSF receptors was prolonged, noncytotoxic but reversible, and not due to endogenous production of GM-CSF. The TGF-beta induced reduction in CSF receptor numbers preceded TGF-beta's growth inhibitory action. In addition, the ED50 (1 to 10 pmol/L) for TGF-beta's CSF receptor modulatory and antiproliferative effect was similar. The effect of TGF-beta on cell surface CSF receptor expression was specific, because the expression of other cell surface proteins (Ly 5 and Ly 17) was not affected by TGF-beta treatment, and because other growth inhibitors (tumor necrosis factor and interferon) did not affect CSF receptor expression. These data suggest that the downregulation of the growth of hematopoietic progenitor cells by TGF-beta involves reducing the cell surface expression on growth factor receptors.

Numbers and percent of T lymphocytes in bovine peripheral blood during the periparturient period

To determine if periparturient immunosuppression in dairy cattle might be due to an alteration in total numbers of percent of T lymphocytes, we examined the numbers and percent of T lymphocyte subsets in peripheral blood from periparturient dairy cows, some of which received recombinant bovine granulocyte colony stimulating factor (rbG-CSF) during the study. Beginning 2 weeks preparatum through 4 weeks postpartum, peripheral blood mononuclear cells (PBMC) were collected and labeled with monoclonal antibodies to BoCD5, BoCD4, and BoCD8, and the percent of cells positive for each marker measured by flow cytometry. The percent of PBMC expressing BoCD5 (total T cells), and BoCD8 (T suppressor/cytotoxic cells) was not significantly different between the groups, or at different times before and after calving. The percent of PBMC expressing BoCD4 (T helper cells) was not significantly different between the groups, however, within both groups there was a higher percent of BoCD4+ cells after calving than during the prepartum period. In cows receiving rbG-CSF, total numbers of PBMC were significantly increased compared to controls during the postpartum treatment period.

Isolation and characterization of the gene encoding a novel, thermostable serine proteinase from the mould Tritirachium album Limber

A number of proteinases are induced and secreted into the culture medium of Tritirachium album Limber when the nitrogen source is limited to exogenous proteins. We have constructed a cDNA library using the polyadenylated RNA isolated during the nutritional induction with bovine serum albumin. A full-length clone of a gene for a new proteinase (named proteinase R) was identified from this library. This clone contained sequences coding for the 108-amino-acid prepro-leader as well as for the 279-amino-acid mature proteinase. Proteinase R apparently belongs to the subtilisin group of serine proteases that contains disulphide bonds. Homology between proteinase R and proteinase K was found to be about 87% at the nucleotide as well as at the amino acid level. The Brookhaven Protein Data Base co-ordinate file of proteinase K was used as a template to study the proteinase R substitutions in three-dimensional space. The majority of the substitutions of proteinase R with respect to proteinase K were found to be on the exterior of the protein model.

A comparison of treatment of canine cyclic hematopoiesis with recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF), G-CSF interleukin-3, and canine G-CSF

Cyclic hematopoiesis in gray collie dogs is a stem cell disease in which abnormal regulation of cell production in the bone marrow causes cyclic fluctuations of blood cell counts. In vitro studies demonstrated that recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and granulocyte colony stimulating factor (G-CSF) all stimulated increases in colony formation by canine bone marrow progenitor cells. Based on these results, gray collie dogs were then treated with recombinant human (rh) GM-CSF, IL-3, or G-CSF subcutaneously to test the hypothesis that pharmacologic doses of one of these hematopoietic growth factors could alter cyclic production of cells. When recombinant canine G-CSF became available, it was tested over a range of doses. In vivo rhIL-3 had no effect on the recurrent neutropenia but was associated with eosinophilia, rhGM-CSF caused neutrophilia and eosinophilia but cycling of hematopoiesis persisted. However, rhG-CSF caused neutrophilia, prevented the recurrent neutropenia and, in the two animals not developing antibodies to rhG-CSF, obliterated periodic fluctuation of monocyte, eosinophil, reticulocyte, and platelet counts. Recombinant canine G-CSF increased the nadir neutrophil counts and amplitude of fluctuations at low doses (1 micrograms/kg/d) and eliminated all cycling of cell counts at high doses (5 and 10 micrograms/kg/d). These data suggest significant differences in the actions of these growth factors and imply a critical role for G-CSF in the homeostatic regulation of hematopoiesis.

cDNA cloning and expression of a metalloproteinase inhibitor related to tissue inhibitor of metalloproteinases

The purification and characterization of a metalloproteinase inhibitor (MI) from bovine aortic endothelial cells, and the demonstration that it is related to, but distinct from, tissue inhibitor of metalloproteinase (TIMP), have previously been reported [De Clerck, Y. A., Yean, T.-D., Ratzkin, B. J., Lu, H.S. & Langley, K. E. (1989) J. Biol. Chem. 264, 17445-17453]. The cDNA cloning of the bovine MI and its human homolog is now reported. The bovine cDNA cloning used probes designed on the basis of NH2-terminal amino acid sequence of bovine MI. The human cDNA cloning in turn used probes representing parts of the bovine cDNA nucleotide sequence. Both cDNAs encode leader sequences of 26 amino acids and mature protein sequences of 194 amino acids. The amino acid sequences of the mature proteins are 94% identical. The human MI cDNA was expressed in Escherichia coli, and a preparation containing anticollagenase activity was recovered. The amino acid sequence of mature human MI is 38% identical to the sequence for human TIMP, and the 12 cysteines in MI and TIMP are aligned almost identically. Thus MI and TIMP comprise an inhibitor family.

Cloning and expression of the gene encoding a novel proteinase from Tritirachium album limber

We have isolated the genomic and cDNA clones encoding a novel proteinase from the fungus Tritirachium album Limber, named proteinase T, synthesis of which is induced in skim milk medium. The coding sequence for this enzyme is interrupted by two introns in the fungal genome. The amino acid sequence of proteinase T as deduced from the nucleotide sequence is about 53% identical to that of proteinase K. Four cysteines are present in the mature proteinase, probably in the form of two disulfide bonds, which might explain the thermal stability of the proteinase. We have expressed the proT cDNA in Escherichia coli. The authenticity of the product has been characterized by Western blotting and N-terminal analysis of the recombinant product.

Disulfide structures of human interleukin-6 are similar to those of human granulocyte colony stimulating factor

The amino acid sequences of human interleukin-6 and granulocyte colony stimulating factor are approximately 30% homologous in the N-terminal region. The relative positions of four half-cystines in human interleukin-6 (IL-6) match four of the five in human granulocyte colony stimulating factor. Labeling experiments of recombinant interleukin-6 with tritiated iodoacetate confirmed that the molecule forms two intramolecular disulfide bonds and contains no detectable level of free sulfhydryls. By isolation and characterization of tryptic and subtilytic peptides obtained from different proteolytic digestions, the disulfide bonds of the IL-6 molecule were assigned to Cys44-Cys50 and Cys73-Cys83. The two disulfide bridges form two small loops which are separated by 22 amino acids. These structures are similar to those of recombinant granulocyte colony stimulating factor.

Disulfide and secondary structures of recombinant human granulocyte colony stimulating factor

Molecular characteristics and secondary structures of recombinant methionyl human granulocyte colony stimulating factor produced by genetically engineered Escherichia coli are described. Limited radiolabeling of the protein with tritiated iodoacetate and determination of the labeled residue revealed that this recombinant protein contains only one free cysteine at position 17 which is not essential for activity. The free cysteine is inaccessible to modification unless the molecule is unfolded under denaturing conditions. The molecule forms two disulfide bridges which were assigned as Cys(36)-Cys(42) and Cys(64)-Cys(74) based on the results of isolation and characterization of disulfide-containing peptides obtained from a subtilisin digest of the intact protein. CD analyses and secondary structure prediction suggest that the molecule is abundant in alpha-helical structures.

In vivo stimulation of granulopoiesis by recombinant human granulocyte colony-stimulating factor

Osmotic pumps containing Escherichia coli-derived recombinant human granulocyte colony-stimulating factor (rhG-CSF) were attached to indwelling jugular vein catheters and implanted subcutaneously into Golden Syrian hamsters. Within 3 days, peripheral granulocyte counts had increased greater than 10-fold with a concomitant 4-fold increase in total leukocytes. Microscopic examination of Wright-Giemsa-stained blood smears from rhG-CSF hamsters showed that only the neutrophil subpopulation of granulocytes had increased. No significant changes in lymphocyte or monocyte counts were observed during the course of continuous rhG-CSF treatment. After subcutaneous injection at rhG-CSF doses of up to 10 micrograms X kg-1 X day-1 only granulocyte counts were affected. However, at higher dose levels, a transient thrombocytopenia was noted. Erythrocyte had lymphocyte/monocyte counts remained unaffected by rhG-CSF over the entire dose range (0.3-300 micrograms X kg-1 X day-1) studied. Total leukocyte counts increased 3-fold within 12 hr after a single s.c. injection of rhG-CSF. This early effect was associated with an increase in the total number of colony-forming cells and the percent of active cycling cells in the marrow. A sustained elevation of peripheral leukocyte and marrow progenitor counts was observed following seven daily s.c. injections of rhG-CSF. The ability of rhG-CSF to increase the production and release of granulocytes from the marrow may underlie the beneficial effect it produced on the restoration of peripheral leukocyte counts in hamsters made leukopenic by treatment with 5-fluorouracil.

Recombinant human granulocyte colony-stimulating factor. Effects on hematopoiesis in normal and cyclophosphamide-treated primates

We examined the in vivo effects of recombinant human granulocyte colony-stimulating factor (rhG-CSF) in primates (cynomolgus monkeys) treated with subcutaneous doses of rhG-CSF for 14-28 d. A dose-dependent increase in the peripheral white blood cells (WBC) was seen, reaching a plateau after 1 wk of rhG-CSF treatment. The elevation of WBC was due to an increase in the absolute neutrophil count. These results demonstrate that rhG-CSF is a potent granulopoietic growth and differentiation factor in vivo. In cyclophosphamide (CY)-induced myelosuppression, rhG-CSF was able to shorten the time period of WBC recovery in two treated monkeys to 1 wk, as compared to more than 4 wk for the control monkey. Its ability to significantly shorten the period of chemotherapy-induced bone marrow hypoplasia may allow clinicians to increase the frequency or dosage of chemotherapeutic agents. In addition, the increase in absolute numbers of functionally active neutrophils may have a profound effect in the rate and severity of neutropenia-related sepsis. Furthermore, the activities reported here indicate a potential role for rhG-CSF in the treatment of patients with myelodysplastic syndrome, congenital agranulocytosis, radiation-induced myelosuppression, and bone marrow transplantation.

Recombinant-DNA-derived bovine growth hormone from Escherichia coli. 1. Demonstration that the hormone is expressed in reduced form, and isolation of the hormone in oxidized, native form

The isolation of bacterially synthesized, recombinant-DNA-derived, bovine growth hormone (r-bGH) with native structure is described. The r-bGH is found in insoluble form, in a pellet fraction, after cell breakage and centrifugation. Cell envelope components (protein, lipid, endotoxin) and nucleic acids are selectively removed from the pellet fraction by an EDTA/lysozyme/deoxycholate extraction. We demonstrate that the r-bGH is largely reduced until solubilized using 6 M guanidine/HCl. Air oxidation is then carried out, in the presence of the guanidine/HCl. The oxidation results in a mixture of about one-third disulfide-linked oligomers and two-thirds oxidized monomer. The latter may include some incorrectly oxidized material, but appears to be mostly correctly oxidized. The oxidized monomer is isolated by gel filtration in the presence of guanidine/HCl. Subsequent guanidine/HCl removal leads to refolded, oxidized r-bGH. All steps in the procedure, in particular the oxidation and refolding steps, can be carried out at relatively high protein concentrations.

Recombinant human granulocyte colony stimulating factor: molecular and biological characterization

Human or rodent bone marrow treated with recombinant human granulocyte colony-stimulating factor (rhG-CSF) in a CFU-GM assay yield predominantly granulocytic colonies. The specificity for granulocyte progenitors in vitro is also demonstrated in vivo by a five- to six-fold elevation in hamster peripheral blood neutrophils. Other cell types (monocytes, lymphocytes and eosinophils) remain stable. Analysis of mRNA from the bladder carcinoma cell line 5637 (1A6) shows the predominant species of mRNA codes for a mature protein of 174 amino acids. A small fraction of the mRNA can code for an alternative form of hG-CSF containing additional three amino acids between positions 35 and 36.

Studies of the human c-myb gene and its product in human acute leukemias

The myb gene is the transforming oncogene of the avian myeloblastosis virus (AMV); its normal cellular homolog, c-myb, is conserved across a broad span of evolution. In humans, c-myb is expressed in malignant hematopoietic cell lines and in primary hematopoietic tumors. Partial complementary DNA clones were generated from blast cells of patients with acute myelogenous leukemia. The sequences of the clones were compared to the c-myb of other species, as well as the v-myb of AMV. In addition, the carboxyl terminal region of human c-myb was placed in an expression vector to obtain protein for the generation of antiserum, which was used to identify the human c-myb gene product. Like v-myb, this protein was found within the nucleus of leukemic cells where it was associated with the nuclear matrix. These studies provide further evidence that c-myb might be involved in human leukemia.

Identification and characterization of the protein encoded by the human N-myc oncogene

The human N-myc gene is related to the c-myc proto-oncogene, and has been shown to have transforming potential in vitro. Many studies have reported amplification of N-myc in human neuroblastoma and retinoblastoma cell lines. In primary tumors, amplification of the gene was found to correlate directly with behavior of the tumor. Specific restriction fragments of a partial complementary DNA clone of N-myc from LA-N-5 human neuroblastoma cells were placed into a bacterial expression vector for the purpose of producing antigens representative of the N-myc protein. Rabbits immunized with these antigens produced antisera that recognized a protein of 62-64 kilodaltons in neuroblastoma cells. By several criteria, this protein appears to be part of the same proto-oncogene family as the c-myc protein. Moreover, the antisera to fragments of this protein were capable of histochemically identifying malignant cells in clinical specimens.

Recombinant human granulocyte colony-stimulating factor: effects on normal and leukemic myeloid cells

Experiments were conducted to isolate and characterize the gene and gene product of a human hematopoietic colony-stimulating factor with pluripotent biological activities. This factor has the ability to induce differentiation of a murine myelomonocytic leukemia cell line WEHI-3B(D+) and cells from patients with newly diagnosed acute nonlymphocytic leukemia (ANLL). A complementary DNA copy of the gene encoding a pluripotent human granulocyte colony-stimulating factor (hG-CSF) was cloned and expressed in Escherichia coli. The recombinant form of hG-CSF is capable of supporting neutrophil proliferation in a CFU-GM assay. In addition, recombinant hG-CSF can support early erythroid colonies and mixed colony formation. Competitive binding studies done with 125I-labeled hG-CSF and cell samples from two patients with newly diagnosed human leukemias as well as WEHI-3B(D+) cells showed that one of the human leukemias (ANLL, classified as M4) and the WEHI-3B(D+) cells have receptors for hG-CSF. Furthermore, the murine WEHI-3B(D+) cells and human leukemic cells classified as M2, M3, and M4 were induced by recombinant hG-CSF to undergo terminal differentiation to macrophages and granulocytes. The secreted form of the protein produced by the bladder carcinoma cell line 5637 was found to be O-glycosylated and to have a molecular weight of 19,600.

Recombinant human granulocyte colony-stimulating factor: effects on normal and leukemic myeloid cells

Experiments were conducted to isolate and characterize the gene and gene product of a human hematopoietic colony-stimulating factor with pluripotent biological activities. This factor has the ability to induce differentiation of a murine myelomonocytic leukemia cell line WEHI-3B(D+) and cells from patients with newly diagnosed acute nonlymphocytic leukemia (ANLL). A complementary DNA copy of the gene encoding a pluripotent human granulocyte colony-stimulating factor (hG-CSF) was cloned and expressed in Escherichia coli. The recombinant form of hG-CSF is capable of supporting neutrophil proliferation in a CFU-GM assay. In addition, recombinant hG-CSF can support early erythroid colonies and mixed colony formation. Competitive binding studies done with 125I-labeled hG-CSF and cell samples from two patients with newly diagnosed human leukemias as well as WEHI-3B(D+) cells showed that one of the human leukemias (ANLL, classified as M4) and the WEHI-3B(D+) cells have receptors for hG-CSF. Furthermore, the murine WEHI-3B(D+) cells and human leukemic cells classified as M2, M3, and M4 were induced by recombinant hG-CSF to undergo terminal differentiation to macrophages and granulocytes. The secreted form of the protein produced by the bladder carcinoma cell line 5637 was found to be O-glycosylated and to have a molecular weight of 19,600.

Application of recombinant DNA technologies to studies on chicken growth hormone

Messenger RNA isolated from chicken pituitaries was used to construct a chicken pituitary cDNA library. A chicken growth hormone cDNA clone was isolated using 32P-labeled mammalian growth hormone cDNA probes. The amino acid sequence (derived from the DNA sequence) of the mature form of chicken growth hormone shows 77% homology with that of bovine growth hormone. The chicken growth hormone cDNA clone was used to generate a vector capable of producing chicken growth hormone in Escherichia coli. The recombinant E. coli-derived chicken growth hormone was similar to pituitary chicken growth hormone in several biochemical and immunological properties. The recombinant-derived hormone has been used to establish a sensitive radioimmunoassay for growth hormone determinations made from chicken sera. The chicken growth hormone gene has also been introduced into a retroviral vector capable of establishing productive infections of chicken cells both in in vitro and in vivo. The resulting infections are accompanied by the production of radioimmunoassay-detectable growth hormone. The concentrations of growth hormone in sera of Leghorn chickens infected with the recombinant retrovirus are three- to tenfold higher than in control animals.

A comparison of the growth-promoting, lipolytic, diabetogenic and immunological properties of pituitary and recombinant-DNA-derived bovine growth hormone (somatotropin)

The physiological mechanisms by which growth hormone (somatotropin) exerts its several metabolic activities remain poorly understood. In particular, there is disagreement as to whether the diabetogenic and lipolytic activities of the hormone are intrinsic properties of the molecule or are the result of contamination with other pituitary components. The availability of recombinant-DNA-derived bovine growth hormone (rebGH) presented an opportunity to compare the biological activities of rebGH and pituitary bGH in the absence of pituitary contaminants. Pituitary bGH and rebGH were immunologically identical in the radioimmunoassay for bGH, and good agreement was obtained for the potency of the latter measured by radioimmunoassay (1.6 units/mg) and the dwarf-mouse bioassay (1.4 units/mg). The lipolytic activity in vitro was examined by measuring the release of glycerol from rat epididymal fat maintained in the presence of dexamethasone (0.2 microgram/ml) and the material to be tested (0.1 and 0.2 mg/ml). Although two preparations of pituitary bGH stimulated a significant (P less than 0.01) increase in glycerol production, neither rebGH nor recombinant-DNA-derived chicken GH was lipolytic. However, when rebGH was intravenously injected into three sheep (0.15 mg/kg), the increase in plasma nonesterified fatty acids was similar to that measured with the same dose of pituitary bGH. Insulin-tolerance tests were conducted in sheep before and after treatment with rebGH and pituitary bGH (four subcutaneous injections of 0.15 mg/kg). Although the effect of rebGH was less than that of the pituitary hormone, both significantly impaired the ability of insulin to lower the concentration of plasma glucose. These data suggest that the lipolytic and diabetogenic activities of bGH are intrinsic properties of the molecule. However, the lipolytic activity may only become apparent after either modification of the molecule in vivo or activation of a lipolytic intermediate.

Stimulation of immunoglobulin secretion in human B lymphocytes as a direct effect of high concentrations of IL 2

In certain human IgM and IgG cell lines, immunoglobulin (Ig) secretion is highly stimulated by a B cell inducing factor (BIF) that is free of interleukin 2 (IL 2). BIF also induces Ig secretion in purified peripheral blood B cell populations that have been mitogenically stimulated by Staphylococcus aureus bacteria. Low concentrations of IL 2 (less than 20 U/ml) are not active in these systems. We now show that IL 2 at concentrations above 100 U/ml can induce Ig secretion in these blood B cells and B cell lines. Both conventional IL 2, purified from the human JURKAT and gibbon MLA-144 cell lines, and recombinant IL 2 are active. Very high concentrations approaching 10(4) U/ml are optimal for Ig secretion. Antibody to the T cell IL 2 receptor, anti-Tac, did not inhibit stimulation of the IgM cell line SKW6.4 by IL 2, and no Tac antigen was detected on the cells. The 9B11 monoclonal anti-IL 2 antibody that neutralizes T cell growth activity also abrogates stimulation of Ig secretion by conventional and recombinant IL 2 in the SKW6.4 cell line. However, the 1H11 monoclonal anti-(conventional thr3-glycosylated IL 2), which does not neutralize T cell growth activity, does inhibit induction of Ig secretion by the corresponding IL 2 in the B cell line. These results suggest that IL 2 stimulates B cells via a low-affinity interaction with a receptor different from the Tac receptor identified on T cells, and that the active site on the IL 2 molecule for B cells differs from that for T cell targets. If IL 2 promotes Ig secretion by binding with a low affinity to the B cell BIF receptor, IL 2 and BIF could be homologous proteins.

Stimulation of immunoglobulin secretion in human B lymphocytes as a direct effect of high concentrations of IL 2

In certain human IgM and IgG cell lines, immunoglobulin (Ig) secretion is highly stimulated by a B cell inducing factor (BIF) that is free of interleukin 2 (IL 2). BIF also induces Ig secretion in purified peripheral blood B cell populations that have been mitogenically stimulated by Staphylococcus aureus bacteria. Low concentrations of IL 2 (less than 20 U/ml) are not active in these systems. We now show that IL 2 at concentrations above 100 U/ml can induce Ig secretion in these blood B cells and B cell lines. Both conventional IL 2, purified from the human JURKAT and gibbon MLA-144 cell lines, and recombinant IL 2 are active. Very high concentrations approaching 10(4) U/ml are optimal for Ig secretion. Antibody to the T cell IL 2 receptor, anti-Tac, did not inhibit stimulation of the IgM cell line SKW6.4 by IL 2, and no Tac antigen was detected on the cells. The 9B11 monoclonal anti-IL 2 antibody that neutralizes T cell growth activity also abrogates stimulation of Ig secretion by conventional and recombinant IL 2 in the SKW6.4 cell line. However, the 1H11 monoclonal anti-(conventional thr3-glycosylated IL 2), which does not neutralize T cell growth activity, does inhibit induction of Ig secretion by the corresponding IL 2 in the B cell line. These results suggest that IL 2 stimulates B cells via a low-affinity interaction with a receptor different from the Tac receptor identified on T cells, and that the active site on the IL 2 molecule for B cells differs from that for T cell targets. If IL 2 promotes Ig secretion by binding with a low affinity to the B cell BIF receptor, IL 2 and BIF could be homologous proteins.