Establishment of IL-5-dependent early B cell lines by long-term bone marrow cultures

Toll-like receptors in sepsis-associated cytokine storm and their endogenous negative regulators as future immunomodulatory targets

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Sepsis infects more than 48.9 million people world-wide, with 19.7 million deaths.

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Cytokine storm plays a significant role in sepsis, along with severe COVID-19.

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TLR signaling pathways plays a crucial role in generating the cytokine storm.

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Endogenous negative regulators of TLR signaling are crucial to regulate cytokine storm.

Cytokine storm generates during various systemic acute infections, including sepsis and current pandemic called COVID-19 (severe) causing devastating inflammatory conditions, which include multi-organ failure or multi-organ dysfunction syndrome (MODS) and death of the patient. Toll-like receptors (TLRs) are one of the major pattern recognition receptors (PRRs) expressed by immune cells as well as non-immune cells, including neurons, which play a crucial role in generating cytokine storm. They recognize microbial-associated molecular patterns (MAMPs, expressed by pathogens) and damage or death-associate molecular patterns (DAMPs; released and/expressed by damaged/killed host cells). Upon recognition of MAMPs and DAMPs, TLRs activate downstream signaling pathways releasing several pro-inflammatory mediators [cytokines, chemokines, interferons, and reactive oxygen and nitrogen species (ROS or RNS)], which cause acute inflammation meant to control the pathogen and repair the damage. Induction of an exaggerated response due to genetic makeup of the host and/or persistence of the pathogen due to its evasion mechanisms may lead to severe systemic inflammatory condition called sepsis in response to the generation of cytokine storm and organ dysfunction. The activation of TLR-induced inflammatory response is hardwired to the induction of several negative feedback mechanisms that come into play to conclude the response and maintain immune homeostasis. This state-of-the-art review describes the importance of TLR signaling in the onset of the sepsis-associated cytokine storm and discusses various host-derived endogenous negative regulators of TLR signaling pathways. The subject is very important as there is a vast array of genes and processes implicated in these negative feedback mechanisms. These molecules and mechanisms can be targeted for developing novel therapeutic drugs for cytokine storm-associated diseases, including sepsis, severe COVID-19, and other inflammatory diseases, where TLR-signaling plays a significant role.

ST2 from rainbow trout quenches TLR signalling, localises at the nuclear membrane and allows the nuclear translocation of MYD88

The mammalian interleukin 1 receptor-like 1 receptor (IL1RL1), commonly known as ST2, is thought to downregulate TLR signalling by sequestering the signalling adapter MYD88 (myeloid differentiation primary response protein 88). ST2 sequences are known in several fish species, but none of them have functionally been examined. We characterised ST2 from rainbow trout (Oncorhynchus mykiss) and the structure of its encoding gene. The primary sequence of ST2 is only weakly conserved from fish to human. However, the amino acid sequences forming the interfaces for ST2 and MYD88 interaction are well conserved throughout evolution. High similarity of the gene segmentation unambiguously proves the common ancestry of fish and mammalian ST2. Trout ST2 and trout MYD88 genes were constitutively expressed in embryonic, larval and adult trout. In vivo infection with Aeromonas salmonicida did not modulate the mRNA levels of both factors. Overexpressing trout ST2 in the mammalian HEK-293 reconstitution system of TLR2 signalling quenched the Escherichia coli-induced activation of NF-κB and SAA promoters in a dose-dependent fashion. The expression of GFP-tagged trout ST2 in human HEK-293 or trout CHSE-214 cells surprisingly revealed that (i) ST2 localised abundantly at the nuclear membrane rather than at the cell membrane and (ii) the coexpression of both ST2 and MYD88 allowed the translocation of trout MYD88 from cytoplasm to nucleus, as assessed using confocal microscopy and Western blotting. Hence, we validated that trout ST2 is a dampener of TLR signalling and interacts with MYD88. The spatial distribution of these factors raises questions about how this repressive mechanism functions.

Total Synthesis of Amphirionin-4

The first total synthesis of amphirionin-4 has been achieved using a combination of cross-coupling strategies to access the polyene side chain and a chlorohydrin-based approach to construct the tetrahydrofuranol core. The remote C9-stereocenter was introduced through a Nozaki-Hiyama-Kishi coupling that proceeded with remote stereoinduction.

Amphirionin-4 with potent proliferation-promoting activity on bone marrow stromal cells from a marine dinoflagellate amphidinium species

A linear polyketide, amphirionin-4 (1), has been isolated from cultivated algal cells of the marine dinoflagellate Amphidinium species. The structure was elucidated on the basis of detailed analyses of 1D and 2D NMR data, and the absolute configurations of C-4 and C-8 were determined using the modified Mosher's method. Amphirionin-4 (1) exhibited extremely potent proliferation-promoting activity on murine bone marrow stromal ST-2 cells (950% promotion) at a concentration of 0.1 ng/mL.

Generation and characterization of rat anti-mouse ST2L monoclonal antibodies

ST2L is a transmembrane receptor that belongs to the IL-1 receptor family. The receptor is expressed on various cell types including Th2 cells, mast cells, basophils, growth-activated fibroblasts, and vascular endothelial cells. ST2L activation by its ligand IL-33 has been implicated in Th2-mediated immunity, inflammation, and allergic responses in vivo. Inhibition of ST2L activity can attenuate Th2-dominated immune responses such as lung eosinophilia, airway hyper-responsiveness, and arthritis in animal models. Here we report the generation and in vitro characterization of a panel of rat anti-mouse ST2L monoclonal antibodies. We demonstrate that the antibodies specifically bind to recombinant receptor protein and that a subset of the binders inhibits mouse ST2L activity in multiple in vitro assays. Four of the identified anti-mouse ST2L antibodies were shown to prevent IL-33 from binding to ST2L, down-regulate IL-33-induced NF-κB signaling, and neutralize the ability of IL-33 to stimulate mouse Th2 cell proliferation. The characterized monoclonal antibodies are important tools that will be used to study mouse ST2L receptor functionality in vivo.

Interleukin-33, a target of parathyroid hormone and oncostatin m, increases osteoblastic matrix mineral deposition and inhibits osteoclast formation in vitro

IL-33 is an important inflammatory mediator in allergy, asthma, and joint inflammation, acting via its receptor, ST2L, to elicit Th₂ cell cytokine secretion. IL-33 is related to IL-1 and IL-18, which both influence bone metabolism, IL-18 in particular inhibiting osteoclast formation and contributing to PTH bone anabolic actions. We found IL-33 immunostaining in osteoblasts in mouse bone and IL-33 mRNA expression in cultured calvarial osteoblasts, which was elevated by treatment with the bone anabolic factors oncostatin M and PTH. IL-33 treatment strongly inhibited osteoclast formation in bone marrow and spleen cell cultures but had no effect on osteoclast formation in receptor activator of nuclear factor-κB ligand/macrophage colony-stimulating factor-treated bone marrow macrophage (BMM) or RAW264.7 cultures, suggesting a lack of direct action on immature osteoclast progenitors. However, osteoclast formation from BMM was inhibited by IL-33 in the presence of osteoblasts, T cells, or mature macrophages, suggesting these cell types may mediate some actions of IL-33. In bone marrow cultures, IL-33 induced mRNA expression of granulocyte macrophage colony-stimulating factor, IL-4, IL-13, and IL-10; osteoclast inhibitory actions of IL-33 were rescued only by combined antibody ablation of these factors. In contrast to osteoclasts, IL-33 promoted matrix mineral deposition by long-term ascorbate treated primary osteoblasts and reduced sclerostin mRNA levels in such cultures after 6 and 24 h of treatment; sclerostin mRNA was also suppressed in IL-33-treated calvarial organ cultures. In summary, IL-33 stimulates osteoblastic function in vitro but inhibits osteoclast formation through at least three separate mechanisms. Autocrine and paracrine actions of osteoblast IL-33 may thus influence bone metabolism.

Interleukin 5 in the link between the innate and acquired immune response

Interleukin-5 (IL-5) is an interdigitating homodimeric glycoprotein that is initially identified by its ability to support the in vitro growth and differentiation of mouse B cells and eosinophils. IL-5 transgenic mouse shows two predominant features, remarkable increase in B-1 cells resulting in enhanced serum antibody levels, predominantly IgM, IgA, and IgE classes and in expansion of eosinophil numbers in the blood and eosinophil infiltration into various tissues. Conversely, mice lacking a functional gene for IL-5 or IL-5 receptor alpha chain (IL-5Ralpha) display a number of developmental and functional impairments in B cells and eosinophils. IL-5 receptor (IL-5R) comprises alpha and betac chains. IL-5 specifically binds to IL-5Ralpha and induces the recruitment of betac to IL-5R. Although precise mechanisms on cell-lineage-specific IL-5Ralpha expression remain elusive, several transcription factors including Sp1, E12/E47, Oct-2, and c/EBPbeta have been shown to regulate its expression in B cells and eosinophils. JAK2 and JAK1 tyrosine kinase are constitutively associated with IL-5Ralpha and betac, respectively, and are activated by IL-5 stimulation. IL-5 activates at least three different signaling pathways including JAK2/STAT5 pathway, Btk pathway, and Ras/ERK pathway. IL-5 is one of key cytokines for mouse B cell differentiation in general, particularly for fate-determination of terminal B cell differentiation to antibody-secreting plasma cells. IL-5 critically regulates homeostatic proliferation and survival of and natural antibody production by B-1 cells, and enhances the AID and Blimp-1 expression in activated B-2 cells leading to induce mu to gamma1 class switch recombination and terminal differentiation to IgM- and IgG1-secreting plasma cells, respectively. In humans, major target cells of IL-5 are eosinophils. IL-5 appears to play important roles in pathogenesis of asthma, hypereosinophilic syndromes, and eosinophil-dependent inflammatory diseases. Clinical studies will provide a strong impetus for investigating the means of modulating IL-5 effects. We will discuss the role of IL-5 in the link between innate and acquired immune response, particularly emphasis of the molecular basis of IL-5-dependent B cell activation, allergen-induced chronic inflammation and hypereosinophilic syndromes on a novel target for therapy.

IL-5 links adaptive and natural immunity specific for epitopes of oxidized LDL and protects from atherosclerosis

During atherogenesis, LDL is oxidized, generating various oxidation-specific neoepitopes, such as malondialdehyde-modified (MDA-modified) LDL (MDA-LDL) or the phosphorylcholine (PC) headgroup of oxidized phospholipids (OxPLs). These epitopes are recognized by both adaptive T cell-dependent (TD) and innate T cell-independent type 2 (TI-2) immune responses. We previously showed that immunization of mice with MDA-LDL induces a TD response and atheroprotection. In addition, a PC-based immunization strategy that leads to a TI-2 expansion of innate B-1 cells and secretion of T15/EO6 clonotype natural IgM antibodies, which bind the PC of OxPLs within oxidized LDL (OxLDL), also reduces atherogenesis. T15/EO6 antibodies inhibit OxLDL uptake by macrophages. We now report that immunization with MDA-LDL, which does not contain OxPL, unexpectedly led to the expansion of T15/EO6 antibodies. MDA-LDL immunization caused a preferential expansion of MDA-LDL-specific Th2 cells that prominently secreted IL-5. In turn, IL-5 provided noncognate stimulation to innate B-1 cells, leading to increased secretion of T15/EO6 IgM. Using a bone marrow transplant model, we also demonstrated that IL-5 deficiency led to decreased titers of T15/EO6 and accelerated atherosclerosis. Thus, IL-5 links adaptive and natural immunity specific to epitopes of OxLDL and protects from atherosclerosis, in part by stimulating the expansion of atheroprotective natural IgM specific for OxLDL.

Effects of a pectic polysaccharide from a medicinal herb, the roots of Bupleurum falcatum L. on interleukin 6 production of murine B cells and B cell lines

The effect of T-cell-independent B cell mitogen, a pectic polysaccharide, bupleuran 2IIc, from a medicinal herb, the roots of Bupleurum falcatum L. on interleukin 6 (IL-6) production of murine B cells and B cell lines was investigated in order to clarify the mechanism of enhanced immunoglobulin (Ig) secretion from B cells. Bupleuran 2IIc enhanced IgM secretion from highly purified murine normal B cells. When normal B cells from murine spleen were cultured with bupleuran 2IIc in the presence of anti-IL-6 neutralizing antibody, the enhanced IgM secretion by bupleuran 2IIc was reduced. When B cells were stimulated with bupleuran 2IIc, their IL-6 secretion and the transcription of IL-6 mRNA were enhanced. The enhanced IL-6 secretion by bupleuran 2IIc was also observed in B cell line, Y16 cell. When bupleuran 2IIc was digested with endo-alpha-(1-->4)-D-polygalacturonase, the resulting enzyme resistant carbohydrate portion, "ramified" region (PG-1) composed of rhamnogalacturonan core containing neutral sugar side chains showed potent IL-6 secretion-enhancing activity. These results suggest that the "ramified" region of bupleuran 2IIc stimulates the secretion of IL-6 as the active site, and the resulting IL-6 may partially contribute the enhancement of IgM secretion as an autocrine and/or paracrine mechanism.

Preparation of recombinant rat interleukin-5 by baculovirus expression system and analysis of its biological activities

Rat interleukin-5 (IL-5) cDNA was subcloned from peritoneal cells collected 4 h after intraperitoneal injection of Ascaris suum antigen solution into the immunized rats. Cysteine proteinase-deleted (CPd) rat IL-5 recombinant virus was constructed by inserting rat IL-5 cDNA into CPd virus having a deletion in the cysteine proteinase gene of the silkworm Bombyx mori nuclear polyhedrosis virus. On infection with the CPd rat IL-5 recombinant virus, the silkworm B. mori larvae produced rat IL-5 as a dimeric form in hemolymph. Recombinant rat IL-5 was purified more than 95.5% by anion-exchange chromatography and hydrophobic chromatography. The purified recombinant rat IL-5 promoted the proliferation of T88-M cells in a concentration-dependent manner, and its effect was inhibited by an anti-murine IL-5 neutralizing polyclonal antibody. When bone marrow cells from normal rats were incubated with recombinant rat IL-5 in medium containing methylcellulose, the colony formation by eosinophilic cells was induced. Furthermore, when rat peritoneal eosinophils were incubated with recombinant rat IL-5, the spontaneous decrease in the eosinophil viability was inhibited in time- and concentration-dependent manners. In addition, the recombinant rat IL-5-induced eosinophil survival was inhibited by an anti-murine IL-5 neutralizing polyclonal antibody. These findings suggest that rat IL-5 acts as B-cell growth factor II (BCGF-II), eosinophil differentiation factor (EDF), and eosinophil survival-enhancing factor.

Intestinal IgA plasma cells of the B1 lineage are IL-5 dependent

Two lineages of B cells, designated B1 and B2 cells, have been identified based upon their origins, anatomical distribution, cell surface markers, antibody repertoire and self-replenishing potential. B1 cells are maintained by self-renewal of cells resident in the peritoneal cavity (PerC) and they utilize a limited repertoire of germline V-region genes, mostly directed against ubiquitous bacterial antigens such as phosphoryl choline (PC). B2 cells are replenished from bone marrow precursors and use a larger repertoire of immunoglobulin V-region genes. Whereas most immunoglobulin A (IgA) plasma cells in the intestine derive from B2 lineage precursors in the Peyer's patch, a subpopulation of Per C-derived B1 cells populate the intestinal lamina propria where they mature into IgA plasma cells. In previous in vivo studies we have shown that whereas IgA+ B2 cells are interleukin (IL)-6 dependent, B1 cells are IL-6 independent. In view of the in vitro evidence that IL-5 is also involved in IgA expression, in the studies reported here we have used IL-5-deficient mice to evaluate the role of IL-5 in vivo in IgA expression in the gut. The results demonstrate that although total IgA cell numbers are only marginally depressed in IL-5-deficient mice, there is a marked selective depletion of IgA+ cells of the B1 lineage in the gut and a corresponding depression in the capacity of these mice to mount an intestinal response to a B1 antigen (PC) but not to a B2 antigen (oralbumin; OVA), reflecting intact B2-derived IgA cell function but a defect in the B1 cell contribution to IgA responses in IL-5 deficient mice. Collectively these data demonstrate differential cytokine regulation of subsets of IgA+ cells in the gut in that IgA+ cells of the B2 lineage are IL-6 dependent but IL-5 independent, but B1-derived IgA+ cells are IL-5 dependent and IL-6 independent.

Interleukin 5 and B cell differentiation

Interleukin-5 (IL-5) stimulates proliferation and differentiation of B cells and eosinophils. IL-5 receptor (IL-5R) comprises alpha and (beta)c chains. IL-5 specifically binds to IL-5Ralpha and induces the recruitment of (beta)c to IL-5Ralpha. JAK2 and JAK1 tyrosine kinases are constitutively associated with hIL-5Ralpha and (beta)c, respectively and activated upon IL-5 stimulation. IL-5 induces tyrosine phosphorylations of cellular proteins including (beta)c and STAT5 and activates Btk. X-linked immunodeficient mice have B-cell-specific defects due to missense mutation of the btk gene. The cytoplasmic proline-rich regions of both IL-5Ralpha and (beta)c are essential for the IL-5 signalling. IL-5 appears to play a critical role in hypereosinophilic syndromes and atopic diseases. The treatment of animals with anti-IL-5 mAb can decrease the enhanced bronchial responsiveness induced by allergen sensitization. Clinical studies provide a strong impetus for investigating the means of modulating IL-5 effects.

Evidence that eosinophil infiltration in the OK-432/fibrinogen-injected Meth-A tumor in mice is mediated by locally produced IL-5

It was previously demonstrated that a single injection of OK-432 (a penicillin-treated freeze-dried Streptococcus) mixed with fibrinogen into cancer tissues induces marked infiltration by eosinophils of the tumor stroma and leads to tumor necrosis. In the present study, we examined mechanisms regulating the local accumulation of eosinophils and the role of infiltrating eosinophils in tumor regression using the OK-432/fibrinogen injected Meth-A fibrosarcoma tumor. After injection of OK-432/fibrinogen into the tumor on the left flank of the BALB/c mice, eosinophil infiltration became obvious in the tumor stroma on day 3 following the accumulation of macrophages and neutrophils, was massive on day 5 and decreased by day 10. After the decrease in the infiltration of eosinophils, the tumor injected with OK-432/fibrinogen diminished markedly in size with ulceration as compared with control. Northern blot analysis revealed that expression of IL-5 mRNA in the tumor tissue was not detected on day 0, was significantly on day 3, reached the maximum on day 5, and thereafter decreased by day 10. Although intraperitoneal injection of rat anti-IL-5 monoclonal antibody in tumor bearing mice prior to OK-432 injection inhibited the infiltration of eosinophils, the antitumor effects of OK-432 persisted. In the blood, neither eosinophilia nor IL-5 activity was recognized during the course of the experiment. These results suggest that intratumoral injection of OK-432/fibrinogen induces local production of IL-5, which in turn recruits eosinophils into the tumor tissue, however, the infiltrating eosinophils do not play an important role in tumor regression.

Defective B-1 cell development and impaired immunity against Angiostrongylus cantonensis in IL-5R alpha-deficient mice

We generated interleukin-5 receptor alpha chain (IL-5R alpha)-deficient (IL-5R alpha-/-) mice by gene targeting. The IL-5R alpha-/- mice showed decreased numbers of B-1 cells concomitant with low serum concentrations of IgM and IgG3. They showed no IL-5-induced enhancement of B cell responses to T-independent antigens. The number of alpha beta T cell receptor-positive thymocytes tended to decrease in 3-week-old IL-5R alpha-/- mice, returning to normal by 6 weeks of age. The IL-5R alpha-/- mice produced basal levels of eosinophils, while their bone marrow cells failed to form eosinophilic colonies in response to IL-5. Impaired eosinophilopoiesis in IL-5R alpha-/-mice enhanced the survival of Angiostrongylus cantonensis. These results indicate that IL-5-induced eosinophils serve as potent effector cells in the killing of Angiostrongylus cantonensis in mice.

Clinical heterogeneity reflects biologic diversity in chronic lymphocytic leukemia

As the incidence of B cell chronic lymphocytic leukemia increases in an aging population, it becomes more important to re-evaluate our understanding of the disease process and current therapy. Previous treatment strategies have been, for the most part, unsuccessful in prolonging survival and thus new approaches are needed. More intense cellular and molecular research on the biologic diversity of this neoplasm will further our understanding of the causes of clinical heterogeneity and refine our ability to predict progression. New approaches, based on alterations of neoplastic cell growth by cytokines or chemotherapeutic agents, may enable clinicians to 'customize' individual treatments based on the stages of CLL B cell differentiation and our understanding of factors involved in the regulation of apoptosis and proliferation at those stages. Taken together, these efforts should ultimately yield much new information that will lead to reduced morbidity and mortality in B-CLL, the most common form of human leukemia.

Novel features of the respiratory tract T-cell response to influenza virus infection: lung T cells increase expression of gamma interferon mRNA in vivo and maintain high levels of mRNA expression for interleukin-5 (IL-5) and IL-10

Analysis of the respiratory tract before and after primary influenza virus infection revealed a virus-induced preferential accumulation of a CD8+ T-cell population that coexpresses mRNA for interleukin-5 (IL-5) and IL-10 with virus dose-dependent high levels of gamma interferon. However, cytokine production in lung tissues was not restricted to the T-cell population, since CD3- cells were found to express mRNA for various cytokines, including IL-4 and particularly IL-6 and granulocyte-macrophage colony-stimulating factor. These data provide in vivo evidence for a local respiratory tract immune response to influenza virus infection dominated by cytokine-producing CD8+ T cells.

Biochemical and functional characterization of soluble form of IL-5 receptor alpha (sIL-5R alpha). Development of ELISA system for detection of sIL-5R alpha

Interleukin-5 (IL-5) mediates pleiotropic functions in various types of cells through its specific receptor (IL-5R) which is composed of two distinct subunits, alpha and beta. In mice, the alpha subunit (IL-5R alpha) specifically binds IL-5 with low affinity. The beta subunit (IL-5R beta) does not bind IL-5 by itself, but constructs the high affinity receptor with IL-5R alpha. We have isolated cDNA encoding the soluble form of IL-5R alpha (sIL-5R alpha). To elucidate the biochemical and functional properties of sIL-5R alpha, we developed an expression system for sIL-5R alpha cDNA in insect cell line Sf21 using baculovirus expression vector and obtained conditioned medium containing large quantities of mouse sIL-5R alpha. Mouse sIL-5R alpha was purified from the conditioned medium by using anti-IL-5R alpha mAb-coupled beads. Immunoaffinity-purified sIL-5R alpha with an approximate molecular mass of 42 kDa inhibited the binding of 125I-labeled IL-5 to IL-5R. By using purified sIL-5R alpha, we prepared rabbit anti-sIL-5R alpha antibody and developed a sandwich ELISA for detection of sIL-5R alpha. Significant amounts of sIL-5R alpha were detected in sera and ascitic fluids of mice bearing tumors (BCL1 and MOPC104E) that responded to IL-5 for DNA synthesis, but not in sera of normal mice. Interestingly, elevated levels of serum sIL-5R alpha were observed in NZB and NZW mice. The sIL-5R alpha may, therefore, have an immunoregulatory role in vivo.

Interleukin-5 expressed by a recombinant virus vector enhances specific mucosal IgA responses in vivo

Several in vitro studies have shown that murine interleukin-5 (mIL-5) enhances IgA production by activated mucosal B cells. To date, however, there is no evidence that this factor significantly up-regulates mucosal IgA responses in vivo. Here, we show that expression of the gene for mIL-5 in a recombinant vaccinia virus vector markedly increases IgA responses to co-expressed heterologous antigen in the lungs of mice given intranasal inocula of the virus. The elevated local IgA responses to vectors expressing mIL-5 peaked at a fourfold higher level than those elicited by control virus at 14 days after infection and were sustained for at least 4 weeks. Increased IgA responses were abrogated in mice treated with monoclonal antibody against mIL-5 and were not detected in systemic lymphoid tissue. No enhancement of specific IgG levels was found either locally or systemically. Our results indicate that mIL-5 selectively enhances the development of mucosal IgA responses in vivo and suggest that expression of this factor in mucosal vaccine vectors may stimulate local immune reactivity.

Maintenance of CD5+ B cells at an early developmental stage by interleukin-5: evidence from immunoglobulin gene usage in interleukin-5 transgenic mice

We have characterized the development and expansion of CD5+ B cells in interleukin-5 (IL-5) transgenic mice in terms of autoantibody production and immunoglobulin gene usage. CD5+IL-5R alpha+ B cells maintained in the presence of IL-5 secreted fewer autoantibodies and had fewer N nucleotides at the 3' end of the D elements compared with CD5- B cells. The reduction in nucleotides, along with the finding that CD5+IL-5R alpha+ B cells in IL-5 transgenic mice use Q52 families more frequently than age-matched control B cells, also suggests that these cells have the characteristics of fetus-type B cells and represent an early stage of B-cell development. All of the VH11 families were expressed with JH1 and the Q52 families were frequently expressed with JH1. Furthermore, JH proximal DQ52 was frequently used in IL-5 transgenic mice. All of these characteristics in terms of immunoglobulin gene usage have been described for CD5+ B cells. These results suggest that IL-5 maintains CD5+ B cells that have a fetus-type of immunoglobulin gene usage. This cytokine could be responsible for prolonging the life span of immature CD5+ B cells, which subsequently mature to CD5- B cells that secrete polyreactive natural antibodies.

Role of the interleukin 5 receptor system in hematopoiesis: Molecular basis for overlapping function of cytokines

Interleukin 5 (IL-5) is a kind of peptide hormone released from T lymphocytes of mammals infected with microorganisms or parasites. It is an acidic glycoprotein with a molecular mass of 40 to 50 kDa that consists of a homodimer of polypeptides. It controls hematopoiesis so that it increases natural immunity. In the mouse, IL-5 acts on committed B cells to induce differentiation into Ig-producing cells and on common progenitors for CD5+ pre-B cells and CD5+ macrophages to support their survival. The antibodies secreted by CD5+ B cells seem to be responsible for the primary protection against the infection with microorganisms or parasites. It also supports the growth and/or differentiation of eosinophil precursor and mature eosinophils, which can be effective for the removal of parasites in combination with the antibodies against them. Murine IL-5 receptor (IL-5R) consists of two different polypeptide chains; alpha chain and beta chain. The IL-5R alpha chain is 60 kDa protein that binds IL-5 with low affinity. The IL-5R beta chain is a 130 kDa protein which does not bind IL-5 by itself but is necessary to form the high affinity IL-5R. The beta chain was identified by using one of the anti-IL-5R mAb and anti-IL-3R mAb as the IL-3R homologue. This beta chain is also used as the beta chain of GM-CSF receptor. This fact suggests that there is a common signaling mechanism among these cytokines and efficient cooperation among them. At the same time, these findings may explain the overlapping role of these cytokines in the development of granulocytes.

Fetal liver pro-B and pre-B lymphocyte clones: expression of lymphoid-specific genes, surface markers, growth requirements, colonization of the bone marrow, and generation of B lymphocytes in vivo and in vitro

We describe here the development and characterization of the FLS4.1 stromal line derived from 15-day fetal liver of BALB/c embryos and defined culture conditions that efficiently support the cloning and long-term growth of nontransformed B-220+ 14-day fetal liver cells at two stages of B-cell development, namely, pro-B lymphocytes (immunoglobulin [Ig] genes in germ line configuration) and pre-B cells (JH-rearranged genes with both light-chain Ig genes in the germ line state). All B-cell precursor clones require recombinant interleukin-7 (rIL-7) and FLS4.1 stromal cells for continuous growth in culture, but pro-B lymphocyte clones can also proliferate in rIL-3. None proliferate in rIL-1, rIL-2, rIL-4, rIL-5, rIL-6, or leukemia inhibitory factor. FLS4.1 stromal cells synthesize mRNA for Steel factor but not for IL-1 to IL-7; all pro-B and pre-B clones express c-Kit, the receptor for Steel factor, and a c-Kit-specific antibody inhibits the enhanced proliferative response of fetal liver B-220+ B-cell precursors supported by FLS4.1 stromal cells and exogenous rIL-7 but does not affect that promoted by rIL-7 alone. Northern (RNA) blot analysis of the expression of the MB-1, lambda 5, Vpre-B, c mu, RAG-1, and RAG-2 genes in pro-B and pre-B clones show that transcription of the MB-1 gene precedes IgH gene rearrangement and RNA synthesis from c mu, RAG-1, RAG-2, lambda 5, and Vpre-B genes. All clones at the pre-B-cell stage synthesize mRNA for c mu, RAG-1, and RAG-2 genes; transcription of the lambda 5 and Vpre-B genes seems to start after D-to-JH rearrangement in B-cell precursors, indicating that the proteins encoded by either gene are not required for B-cell progenitors to undergo D-to-JH gene rearrangement. These findings mark transcription of the MB-1 gene as one of the earliest molecular events in commitment to develop along the B-lymphocyte pathway. Indeed, both pro-B and pre-B clones can generate in vitro and in vivo B lymphocytes but not T lymphocytes; moreover, these clones do not express the CD3-gamma T-cell-specific gene, nor do they have rearranged gamma, delta, or beta T-cell antigen receptor genes.

Fetal liver pro-B and pre-B lymphocyte clones: expression of lymphoid-specific genes, surface markers, growth requirements, colonization of the bone marrow, and generation of B lymphocytes in vivo and in vitro

We describe here the development and characterization of the FLS4.1 stromal line derived from 15-day fetal liver of BALB/c embryos and defined culture conditions that efficiently support the cloning and long-term growth of nontransformed B-220+ 14-day fetal liver cells at two stages of B-cell development, namely, pro-B lymphocytes (immunoglobulin [Ig] genes in germ line configuration) and pre-B cells (JH-rearranged genes with both light-chain Ig genes in the germ line state). All B-cell precursor clones require recombinant interleukin-7 (rIL-7) and FLS4.1 stromal cells for continuous growth in culture, but pro-B lymphocyte clones can also proliferate in rIL-3. None proliferate in rIL-1, rIL-2, rIL-4, rIL-5, rIL-6, or leukemia inhibitory factor. FLS4.1 stromal cells synthesize mRNA for Steel factor but not for IL-1 to IL-7; all pro-B and pre-B clones express c-Kit, the receptor for Steel factor, and a c-Kit-specific antibody inhibits the enhanced proliferative response of fetal liver B-220+ B-cell precursors supported by FLS4.1 stromal cells and exogenous rIL-7 but does not affect that promoted by rIL-7 alone. Northern (RNA) blot analysis of the expression of the MB-1, lambda 5, Vpre-B, c mu, RAG-1, and RAG-2 genes in pro-B and pre-B clones show that transcription of the MB-1 gene precedes IgH gene rearrangement and RNA synthesis from c mu, RAG-1, RAG-2, lambda 5, and Vpre-B genes. All clones at the pre-B-cell stage synthesize mRNA for c mu, RAG-1, and RAG-2 genes; transcription of the lambda 5 and Vpre-B genes seems to start after D-to-JH rearrangement in B-cell precursors, indicating that the proteins encoded by either gene are not required for B-cell progenitors to undergo D-to-JH gene rearrangement. These findings mark transcription of the MB-1 gene as one of the earliest molecular events in commitment to develop along the B-lymphocyte pathway. Indeed, both pro-B and pre-B clones can generate in vitro and in vivo B lymphocytes but not T lymphocytes; moreover, these clones do not express the CD3-gamma T-cell-specific gene, nor do they have rearranged gamma, delta, or beta T-cell antigen receptor genes.

Molecular cloning and expression of the human interleukin 5 receptor

Human interleukin 5 (IL-5) plays an important role in proliferation and differentiation of human eosinophils. We report the isolation of cDNA clones from cDNA libraries of human eosinophils by using murine IL-5 receptor alpha chain cDNA as a probe. Analysis of the predicted amino acid sequence indicated that the human IL-5 receptor has approximately 70% amino acid sequence homology with the murine IL-5 receptor and retains features common to the cytokine receptor superfamily. One cDNA clone encodes a glycoprotein of 420 amino acids (Mr 47,670) with an NH2-terminal hydrophobic region (20 amino acids), a glycosylated extracellular domain (324 amino acids), a transmembrane domain (21 amino acids), and a cytoplasmic domain (55 amino acids). Another cDNA encodes only the extracellular domain of this receptor molecule. Other cDNA clones encode molecules having diversified cytoplasmic domains. COS7 cells transfected with the cDNA expressed a approximately 60-kD protein and bound IL-5 with a single class of affinity (Kd = 250-590 pM). The Kd values were similar to that observed in normal human eosinophils. In contrast to the murine 60-kD alpha chain, which binds IL-5 with low affinity (Kd = approximately 10 nM), the human alpha chain homologue can bind IL-5 with much higher affinity by itself. RNA blot analysis of human cells demonstrated two transcripts (approximately 5.3 and 1.4 kb). Both of them were expressed in normal human eosinophils and in erythroleukemic cell line TF-1, which responds to IL-5. The human IL-5 receptor characterized in this paper is essential for signal transduction, because expression of this molecule in murine IL-3-dependent cell line FDC-P1 allowed these cells to proliferate in response to IL-5.

NZB serum factor (NZB-SF)-B precursor cell maturation factor. II. In vivo effects of NZB-SF or mAb against NZB-SF on B lineage cell populations

In vivo effects of NZB serum factor (NZB-SF), which enhances the maturation of B precursor cells in vitro, were examined. Immunoaffinity-purified NZB-SF from young NZB mice was injected into B6 mice intraperitoneally twice weekly, five times total (5 micrograms/dose/mouse). Control mice were given 0.01% albumin. Then the B lineage cell populations defined phenotypically (sIg+ cells, B220+ cells, and AA4.1+ cells) or the numbers of colony-forming B lineage cells were examined. NZB-SF-treated B6 mice exhibited a decrease in the percentage of B precursor cells in marrow, even though the percentage of sIg+ cells in marrow or spleen did not differ from controls. In contrast, the frequency of colony-forming B cells in marrow and spleen, especially sIg- colony-forming B cells in marrow, increased significantly in NZB-SF-treated mice as compared to controls. In addition, monoclonal antibody (mAb) against NZB-SF was injected weekly for 9 weeks into NZB mice beginning at 7 weeks of age. mAb vs NZB-SF at a dose of 5 micrograms per mouse per injection, as stated above, prevented the decline of sIg- colony-forming B lineage cells which usually occurred in the adult NZB mice (greater than 16 weeks). This treatment also prevented, in part, the decline of the B220+ cell population which normally occurs in the marrow with increasing age. Thus NZB-SF impressively influences the composition of B lineage cell populations in normal B6 mice and may account for abnormal changes of B lineage cell populations observed in NZB mice.

Amino acid sequence analysis of a mouse interleukin 5 receptor protein reveals homology with a mouse interleukin 3 receptor protein

A polypeptide chain for the mouse interleukin 5 receptor (IL5R) was purified from detergent-lysed B13 cells, a mouse IL5-dependent pre-B cell line. Purification was by a single immunoaffinity chromatographic step using an anti-mouse IL5R monoclonal antibody, R52. Internal amino acid sequence was obtained from four trypsin-generated peptides. All peptides were found to be present in the published amino acid sequence of a mouse IL3R and the mouse IL3R-like protein deduced from the cDNA. This indicates that the mouse IL5R and the mouse IL3R have a homologous polypeptide in common and suggests that the specificity of these lymphokine receptors is mainly generated by association with another ligand-specific polypeptide chain.

Transgenic mice expressing a B cell growth and differentiation factor gene (interleukin 5) develop eosinophilia and autoantibody production

Interleukin 5 (IL-5) has been suggested to be involved in the growth and differentiation of B cells and eosinophils. Especially, Ly-1+ B cells, which have been considered to produce autoantibodies, are selectively developed by this lymphokine in long-term bone marrow culture. To envisage the possible engagement of IL-5 in the development of these cells in vivo, transgenic mice carrying the mouse IL-5 gene ligated with a metallothionein promoter were generated. Transgenic mice carrying the IL-5 gene exhibited elevated levels of IL-5 in the serum and an increase in the levels of serum IgM and IgA. A massive eosinophilia in peripheral blood, bone marrow, and spleen, and an infiltration of muscle and liver with eosinophils, were observed. When cadmium-containing saline was injected intraperitoneally into transgenic mice, IL-5 production was augmented about five times within 24 h, and a distinctive Ly-1+ B cell population became apparent in the spleen after 5 d. IL-5 receptors were detected on those cells by monoclonal antibodies against IL-5 receptors. Another interesting finding in these transgenic mice was an increase in polyreactive anti-DNA antibodies of IgM class. It is suggested, therefore, that aberrant expression of the IL-5 gene may induce accumulation of Ly-1+ B cells and eosinophils. Furthermore, this IL-5 transgenic mouse can be a model mouse for eosinophilia, and we can determine the role of IL-5 in the differentiation of Ly-1+ B cells and eosinophils by using this mouse.

Interleukin 5 and its receptor

IL-5 is a cytokine mainly produced by T lymphocytes, especially when they are sensitized with microorganisms, which induce eosinophils and Ly-1 positive B lineage cells, both of which are probably engaged in the primary protection against micro-organisms. These possibilities are discussed by analyzing IL-5 transgenic mice. We also discuss the possibility of using these mice as animal models for the diseases which may be caused by increased levels of eosinophils. Although IL-5 is not produced by bone marrow stromal cells, it is involved in the early development of eosinophils and Ly-1 positive B-lineage cells that can differentiate into macrophages. The clue to the role of IL-5 may exist in the constitution of IL-5 receptor. The IL-5 receptor consists of alpha and beta chains. The alpha chain is a 60 kDa glycosylated protein which binds IL-5, by itself, with low affinity. On the other hand, the 130 kDa beta chain does not bind IL-5 by itself, but forms high affinity IL-5 receptors together with the alpha chain. Surprisingly, this beta chain is probably shared with the GM-CSF receptor and is very homologous to the IL-3 receptor. It seems that the beta chain is expressed in the very early stage of hematopoiesis. The alpha chain may be directly related to the cell lineage commitment.

Interleukin 5 and interleukin 3 induce serine and tyrosine phosphorylations of several cellular proteins in an interleukin 5-dependent cell line

Murine interleukin 5 (IL-5), a lymphokine produced by helper T cells, is involved in the regulation of growth and differentiation of B cells and eosinophils. To elucidate the intracellular events via the IL-5 receptor, we have investigated IL-5-induced protein phosphorylation in an IL-5-dependent murine early B-lineage cell line (T88-M). The rapid phosphorylation of a 60-kDa protein at serine residues and of 140-, 92-, 53-, 48-, and 45-kDa proteins at tyrosine residues were induced by the stimulation of T88-M cells with IL-5. T88-M cells were found to proliferate in response to IL-3 as well as IL-5, and the phosphoproteins in T88-M cells could be induced by IL-3 stimulation in a similar manner of those induced by IL-5. Thus, these results suggest that the protein phosphorylation events in T88-M cells may be shared by both pathways via the IL-5 receptor and the IL-3 receptor.

Retroviral interleukin 5 gene transfer into interleukin 5-dependent growing cell lines results in autocrine growth and tumorigenicity

Two interleukin 5 (IL5)-specific retroviral expression vectors have been constructed containing the neomycin gene as selectable marker and either the mouse IL5 cDNA region or the rat genomic IL5 gene under the control of the thymidine kinase promoter. High viral titer supernatants derived from the transfected or infected packaging cell line psi 2 were used to infect the two cell lines B13 and T88M whose growth is dependent on exogenous IL 5. Infection resulted in G418 resistance and IL 5-independent growth with a high frequency. Clones were established which secrete between 2 and greater than 1000 U IL5. The proliferation of the IL5 autocrine growing cells could be inhibited by an antibody directed against the IL5 receptor indicating that they grow as a result of the endogenously produced IL5. Regardless of the amount of IL5 they produced, all of the clones were highly tumorigenic in nucle mice. The phenotype of the tumors was indistinguishable from that of the injected cells. T88M or B13 cells infected with a control virus neither produced IL5, nor became factor independent, nor produced tumors. Together, the IL5 gene transfer and expression into IL5-dependent growing cells are in accordance with the "autocrine growth" hypothesis and contrast analogous experiments with IL4.

Elevated expression of proto-oncogenes during interleukin-5-induced growth and differentiation of murine B lineage cells

Interleukin 5 (IL-5), a lymphokine produced by helper T cells, is involved in the regulation of growth and differentiation of B cells and other hematopoietic cells. To elucidate IL-5-mediated intracellular mechanisms, we have established IL-5-dependent and -independent murine early B cell lines, J6 and MJ88-1, respectively, and examined the effect of IL-5 on the expression of proto-oncogenes during proliferation. Two- to 3.5-fold increases in the levels of c-myb, c-myc, c-fos, and c-fms mRNA were observed in J6 cells, compared with those in MJ88-1 cells. Further, a role of IL-5 in the proto-oncogene expression during differentiation was examined by using thymidine-treated murine B-cell chronic leukemia BCL1-B20 cells with growth arrest. After 4-day culture, the amount of IgM secreted from BCL1-B20 cells was augmented 4-6 fold in the presence of IL-5. Although expression of c-myb, c-fos, and c-fms mRNA did not change, only c-myc mRNA expression was elevated within 30 min of stimulation with IL-5 and reached a maximal level by 1 hr. Addition of phorbol 12-myristate 13-acetate (PMA) or IL-4 to the culture of BCL1-B20 cells inhibited both the IL-5-mediated augmentation of IgM secretion and the elevated expression of c-myc mRNA. These findings suggest that the IL-5 signal may be associated with the up-regulation of c-myc expression.

Structural comparison of murine T-cell (B151K12)-derived T-cell-replacing factor (IL-5) with rIL-5: dimer formation is essential for the expression of biological activity

T-cell-replacing factor (TRF)/IL-5 is a T-cell-derived glycoprotein which has pleiotropic activity on lymphoid and myeloid cells. IL-5 polypeptide translated into Xenopus oocytes are heterogeneous in molecular size (40,000 to 60,000 under nonreducing conditions) and yields a monomeric form (Mr of 25,000 to 30,000) under reducing conditions (J. Immun., 140, 1175-1181, 1988). We purified T-cell-derived TRF and rIL-5 using anti-TRF/IL-5 antibody-coupled affinity column from supernatants of a T-cell hybridoma B151K12 and supernatants of HeLa cells, respectively, which had been transfected with murine IL-5 cDNA, and determined their partial N-terminal amino acid sequence (27 residues for B151-TRF and 13 residues for rIL-5). A single amino acid sequence of each sample obtained beginning from methionine that was identical to that predicted from IL-5 cDNA. This finding supports the notion that secreted B151-TRF polypeptide consists of 113 amino acids. Purified B151-TRF supported eosinophilopoiesis of human bone marrow cells as effective as mouse rIL-5 and human rIL-5. B151-TRF competitively inhibited 35S-labeled rIL-5 binding to target cells to the same extent at rIL-5. Treatment of purified rIL-5 and B151-TRF with reducing reagents such as 2-ME, sodium borohydride or dithiothreitol produced a monomeric form of IL-5 which did not exert a biological activity. Reduction and alkylation of rIL-5 caused the loss of binding to its target cells. These results strongly suggest that B151-TRF exists as a homodimer and its primary structure and secondary structures are identical to those of rIL-5. Moreover, the formation of inter-molecular disulfide bond(s) linked by two pairs of cystein residues is essential for the expression of the biological activity of mouse IL-5.

Rapid methods for purification of human recombinant interleukin-5 (IL-5) using the anti-murine IL-5 antibody-coupled immunoaffinity column

A large scale production of human recombinant IL-5 (hIL-5) was performed by way of recombinant DNA technology. In this study, we transfected Chinese hamster ovary cells with pdKCR-hIL-5gene-dhfr plasmid and selected a cell line, with the use of methotrexate, producing large amounts of hIL-5. The recombinant hIL-5 thus obtained induced IgM production of murine B cell leukemia BCL1, and its activity was inhibited by TB13 anti-mouse IL-5 monoclonal antibody. hIL-5 could be purified from the cell-free supernatants of the transfectants with high recoveries by using anti-mouse IL-5 antibody-coupled immunoaffinity column in combination with a gel permeation column chromatography. N terminal amino acid sequence analysis of purified hIL-5 revealed that a single amino-terminal amino acid (isoleucine) is detected and hIL-5 consists of 115 amino acid residues.

Expression vector system based on the chicken beta-actin promoter directs efficient production of interleukin-5

We examined the promoter activity of the 1.3-kb chicken beta-actin gene sequence located between the 5' flanking region and the proximal region of the second exon. This promoter region showed higher promoter activity than the simian virus 40 (SV40) early promoter or the Rous sarcoma virus (RSV) long terminal repeat (LTR) as assayed by transient lacZ gene expression in mouse L cells. Furthermore, replacement of the 3' splice sequence in this promoter by that derived from the rabbit beta-globin gene resulted in a approximately 2.5-fold enhancement in the synthesis of beta-galactosidase (beta Gal). Introduction of the SV40 origin of DNA replication (ori) into the vector carrying this hybrid promoter, which we designate the AG promoter, markedly enhanced the production of beta Gal in an SV40 T antigen-producing cell, BMT10. We have constructed a useful vector containing the strong AG promoter, several unique restriction sites, a SV40 polyadenylation signal and the SV40 ori for transient expression of cDNA in BMT10 or COS cells. We demonstrate the use of this vector for efficient production of interleukin-5 in BMT10 cells.