The biology of interleukin-5 and its receptor

Role of IL-5 in asthma and airway remodelling

Asthma is a common and burdensome chronic inflammatory airway disease that affects both children and adults. One of the main concerns with asthma is the manifestation of irreversible tissue remodelling of the airways due to the chronic inflammatory environment that eventually disrupts the whole structure of the airways. Most people with troublesome asthma are treated with inhaled corticosteroids. However, the development of steroid resistance is a commonly encountered issue, necessitating other treatment options for these patients. Biological therapies are a promising therapeutic approach for people with steroid-resistant asthma. Interleukin 5 is recently gaining a lot of attention as a biological target relevant to the tissue remodelling process. Since IL-5-neutralizing monoclonal antibodies (mepolizumab, reslizumab and benralizumab) are currently available for clinical use, this review aims to revisit the role of IL-5 in asthma pathogenesis at large and airway remodelling in particular, in addition to exploring its role as a target for biological treatments.

Impaired T-lymphocyte proliferation function in biliary atresia patients with chronic cholestatic jaundice after a Kasai operation

To investigate the association between chronic cholestatic jaundice, systemic immunity, and various infectious complications in patients with biliary atresia (BA), we performed a survey of the systemic immune function in 30 children with BA. Patients were divided into a jaundice group (total serum bilirubin > or = 2 mg/dL for >6 mo) and control group (total serum bilirubin <2 mg/dL for >6 mo) with comparable age. Patients were tested for serum immunoglobulin and complement levels, mitogen response, interleukin (IL)-4, IL-5, and interferon-gamma production after phytohemagglutinin (PHA) stimulation, blood cell and lymphocyte subpopulation counts, phagocytic function, and leukocyte adhesion complex. They were then followed prospectively for 6 mo, and severe infectious complications requiring hospitalization were recorded. Compared with jaundice-free patients, T-lymphocyte proliferation function, determined by PHA mitogen test was significantly lower (p = 0.02) in BA patients with chronic cholestatic jaundice after a Kasai operation. During the study period, patients with chronic cholestatic jaundice had a higher risk of severe infectious complications than their jaundice-free counterparts (risk ratio = 5.87; p = 0.001). In conclusion, BA patients with chronic cholestatic jaundice are associated with impairment of T-lymphocyte proliferation and increased incidence of severe infectious complications.

Interleukin-5 inhibition of biliary cell chloride currents and bile flow

Recent studies have detected significant elevations of interleukin (IL)-5 mRNA in the liver parenchyma of patients with both primary biliary cirrhosis and acute rejection after liver transplantation. In both of these disorders, intrahepatic biliary epithelial cells (BECs) are the targets of injury. We hypothesized that BECs may themselves express IL-5 receptors that may modulate key biliary functions. RNAs coding for IL-5alpha and -beta receptors were amplified by RT/PCR from a biliary cell line derived from a human cholangiocarcinoma (Mz-ChA-1) and verified by DNA sequencing. IL-5 receptor distribution was detected immunocytochemically on Mz-ChA-1 cells, immortalized murine BEC, bile duct-ligated rat liver, and isolated cholangiocytes. Patch-clamp studies on Mz-ChA-1 cells showed that IL-5 inhibits 5'-N-ethylcarboxamidoadenosine-stimulated chloride currents. Additional functional studies showed that IL-5 inhibits secretin-induced bile flow. We conclude that BECs express IL-5 receptors and that IL-5 modulates BEC chloride currents and fluid secretion. Since IL-5 has previously been associated with cholestatic liver disease, we speculate that IL-5 may contribute to liver injury through its effects on biliary secretion.

In vitro and in vivo inhibition of interleukin (IL)-5-mediated eosinopoiesis by murine IL-5Ralpha antisense oligonucleotide

The unique role of interleukin (IL)-5 in eosinophil production, activation, and localization makes this cytokine a prime target for therapeutic intervention in diseases characterized by a selective blood and tissue eosinophilia. In an attempt to block the effects of IL-5 on eosinophils, a strategy was developed to suppress the expression of the IL-5 receptor alpha chain (IL-5Ralpha) by antisense oligonucleotides (ASOs). IL-5Ralpha ASOs were identified which selectively and specifically suppress the expression of messenger RNA and proteins of both the membrane and the soluble form of the receptor in constitutively IL-5R-expressing murine BCL-1 cells in vitro. Moreover, these IL-5Ralpha-specific ASOs were able to selectively inhibit the IL-5-induced eosinopoesis from murine fetal liver and bone marrow cells in vitro, suggesting that these molecules may affect the development of IL-5-mediated eosinophilia in vivo. Indeed, intravenous administration of IL-5Ralpha-specific ASOs not only suppressed the bone-marrow and blood eosinophilia in mice after short-term treatment with recombinant murine IL-5 but also inhibited the development of blood and tissue eosinophilia in a ragweed-induced allergic peritonitis model. Thus, blocking the expression of IL-5Ralpha on eosinophil using ASOs may have therapeutic benefits in eosinophilic diseases such as asthma.

Bullous pemphigoid: interaction of interleukin 5, anti-basement membrane zone antibodies and eosinophils. A preliminary observation

Bullous pemphigoid (BP) is an autoimmune blistering skin disease characterized by the presence of autoantibodies to normal components of the hemidesmosome (BPAg1 and BPAg2). Histology of skin lesions demonstrate a subepidermal vesicle and a predominantly eosinophilic dermal cellular infiltrate. Interleukin 5 (IL-5) plays a major role in eosinophil recruitment and function. Using an ELISA, we investigated the levels of IL-5 in the sera and blister fluid of BP patients with active disease and those in prolonged clinical remission treated with intravenous immunoglobulin, and compared it to that in normal controls. Significantly increased levels of IL-5 were detected in the serum and particularly the blister fluid of patients with active disease (P=0.0043) when compared to levels in normal controls. There was no significant difference in IL-5 levels in patients in prolonged clinical remission compared to normal control serum. In an immunoblot assay, using bovine gingival lysate as substrate, we determined the presence of IgG and IgE autoantibodies specific to basement membrane zone proteins in blister fluid and serum of BP patients. IgG autoantibodies to BPAg1 and BPAg2 were detected in both blister fluid and serum of patients, whereas IgE autoantibodies, in much lower titers, were detected to only BPAg1. Elevated levels of blood and tissue eosinophilia were observed in these patients. Based on these data, we present a preliminary hypothesis for the initiation, progression and localization of blister formation in BP.

Protective role for interleukin-5 during chronic Toxoplasma gondii infection

To investigate the role of interleukin-5 (IL-5) during Toxoplasma gondii infection, IL-5 knockout (KO) mice and C57BL/6 control mice were infected intraperitoneally with ME49 cysts and the course of infection was monitored. The mortality rate during chronic infection was significantly greater in IL-5-deficient animals, and consistent with this finding, the KO mice harbored a greater number of brain cysts and tachyzoites than did their wild-type counterparts. Although the IL-5 KO animals did not succumb until late during infection, increased susceptibility, as measured by accelerated weight loss, was detectable during the acute stages of infection. The amounts of total immunoglobulin (Ig), IgM, and IgG2b were comparable in both strains, while the amount of IgG1 was much smaller in IL-5 KO mice. Spleen cell production of IL-12 in response to T. gondii antigen was approximately threefold lower in the KO strain, and this decrease correlated with a selective loss of B lymphocytes during culture. A link between the presence of B cells and augmented IL-12 production was established by the finding that after removal of B cells with monoclonal antibody and complement, wild-type- and KO-derived cells produced equivalent levels of IL-12 in response to T. gondii antigen. These results demonstrate a protective role of IL-5 against T. gondii infection and suggest that IL-5 may play a role in the production of IL-12.

Characterization of skin cytokines in bullous pemphigoid and pemphigus vulgaris

The purpose of this study was to determine cytokine and cell marker expression in perilesional skin biopsies from patients with the autoimmune blistering diseases bullous pemphigoid (BP, n = 21) and pemphigus vulgaris (PV, n = 7). Immunohistochemistry and in situ hybridization were used to detect T helper (Th)1 [interleukin (IL)-2, interferon (IFN)-gamma] and Th2 (IL-4, IL-5, IL-13) protein and mRNA. Perilesional skin biopsies from patients with BP were characterized by the deposition of IL-4, IL-13 and IL-5. In patients with BP, IL-4 and IL-13 localized to mononuclear cells within the dermal infiltrate while IL-5 was predominately expressed at the dermal-epidermal junction. BP skin sections also expressed vascular cell adhesion molecule 1 on endothelial cells, not seen in patients with PV. PV biopsies were remarkable for a mixed Th1/Th2 pattern of cytokine expression, including the presence of IL-2, IFN-gamma and IL-4 and the absence of IL-5 and IL-13. In situ hybridization detected mRNA for IL-4 and IL-5 in the cellular infiltrate of BP patients, and IL-2 in a patient with PV. In vitro binding assays demonstrated that normal human eosinophils, activated by coculture in IL-5, bound preferentially to BP skin sections that contained detectable in vivo bound IL-5. The predominance of Th2 cytokines in BP, in association with increased binding of eosinophils in vitro, suggests that Th2 cytokines are relevant in the recruitment and adhesion of eosinophils within the dermal infiltrates of patients with BP, and may play a part in the pathogenesis of blister formation.

Biology of IL-5 in health and disease

LEARNING OBJECTIVES

Reading this article will increase the readers' knowledge of the biology of interleukin-5 (IL-5), an important cytokine. The immune and inflammatory responses of any organism are the basis of the defense mechanism ensuring its survival. The role of IL-5 in these processes, as well as in the pathogenesis of various diseases has been discussed along with the effects of various pharmacologic agents on the production and function of IL-5.

DATA SOURCES

A detailed literature search was performed. Studies considered relevant and important, in all languages, which involved humans and animals were used.

STUDY SELECTION

Information was obtained only from peer reviewed journals.

RESULTS

Interleukin-5 is normally produced by T-cells, mast cells, and eosinophils while Reed Sternberg and Epstein Barr virus (EBV) transformed cells also produce IL-5. Monoclonal antibodies (mAb) to IL-5 are potent inhibitors of IL-5 mediated tissue damage, secondary to eosinophil infiltration. The majority of the studies on IL-5 are preliminary, often the information is obtained from animal studies or in vitro systems and occasionally from pathologic tissue analysis. This along with the absence of confirmatory studies is a limiting factor. Nonetheless, the role of IL-5 in allergic and immunologic disease and asthma may be central to their pathogenesis.

CONCLUSIONS

Interleukin-5 is an important molecule that is participant to many processes that maintain health and are involved directly or indirectly in the pathogenesis of disease. Some pharmacologic agents can modify IL-5 production in vivo. Development of selective inhibitors of IL-5 may have a potential use for specific therapy of certain autoimmune, inflammatory, and neoplastic diseases.

IL-5 and IL-5 receptor in asthma

Eosinophils, along with mast cells are key cells involved in the innate immune response against parasitic infection whereas the adaptive immune response is largely dependent on lymphocytes. In chronic parasitic disease and in chronic allergic disease, IL-5 is predominantly a T cell derived cytokine which is particularly important for the terminal differentiation, activation and survival of committed eosinophil precursors. The human IL-5 gene is located on chromosome 5 in a gene cluster that contains the evolutionary related IL-4 family of cytokine genes. The human IL-5 receptor complex is a heterodimer consisting of a unique alpha subunit (predominantly expressed on eosinophils) and a beta subunit which is shared between the receptors for IL-3 & GM-CSF (more widely expressed). The alpha subunit is required for ligand-specific binding whereas association with the beta subunit results in increased binding affinity. The alternative splicing of the alpha IL-5R gene which contains 14 exons can yield several alpha-IL-5R isoforms including a membrane-anchored isoform (alpha IL-5Rm) and a soluble isoform (alpha IL-5Rs). Cytokines such as IL-5 produce specific and non-specific cellular responses through specific cell membrane receptor mediated activation of intracellular signal transduction pathways which, to a large part, regulate gene expression. The major intracellular signal transduction mechanism is activation of non-receptor associated tyrosine kinases including JAK and MAP kinases which can then transduce signals via a novel family of transcriptional factors named signal transducers and activators of transcription (STATS). JAK2, STAT1, and STAT5 appear to be particularly important in IL-5 mediated eosinophil responses. Asthma is characterized by episodic airways obstruction, increased bronchial responsiveness, and airway inflammation. Several studies have shown an association between the number of activated T cells and eosinophils in the airways and abnormalities in FEV1, airway reactivity and clinical severity in asthma. It has now been well documented that IL-5 is highly expressed in the bronchial mucosa of atopic and intrinsic asthmatics and that the increased IL-5 mRNA present in airway tissues is predominantly T cell derived. Immunocytochemical staining of bronchial biopsy sections has confirmed that IL-5 mRNA transcripts are translated into protein in asthmatic subjects. Furthermore, the number of activated CD4 + T cells and IL-5 mRNA positive cells are increased in asthmatic airways following antigen challenge and studies that have examined IL-5 expression in asthmatic subjects before and after steroids have shown significantly decreased expression following oral corticosteroid treatment in steroid-sensitive asthma but not in steroid resistant and chronic severe steroid dependent asthma. The link between T cell derived IL-5 and eosinophil activation in asthmatic airways is further strengthened by the demonstration that there is an increased number of alpha IL-5R mRNA positive cells in the bronchial biopsies of atopic and non-atopic asthmatic subjects and that the eosinophil is the predominant site of this increased alpha IL-5R mRNA expression. We have also shown that the subset of activated eosinophils that expressed mRNA for membrane bound alpha IL-5r inversely correlated with FEV1, whereas the subset of activated eosinophils that expressed mRNA for soluble alpha IL-5r directly correlated with FEV1. Hence, not only does this data suggest that the presence of eosinophils expressing alpha IL-5R mRNA contribute towards the pathogenesis of bronchial asthma, but also that the eosinophil phenotype with respect to alpha IL-5R isoform expression is of central importance. Finally, there are several animal, and more recently in vitro lung explant, models of allergen induced eosinophilia, late airway responses (LARS), and bronchial hyperresponsiveness (BHR)--all of which support a link between IL-5 and airway eosinophilia and bronc

Selective Inhibition of IL-5 Receptor α-Chain Gene Transcription by IL-5, IL-3, and Granulocyte-Macrophage Colony-Stimulating Factor in Human Blood Eosinophils

High affinity receptor for IL-5 (IL-5R), a predominant eosinophil maturation factor, is composed of an IL-5-binding α-chain (IL-5Rα) and a signal-transducing β-chain that is shared by IL-3 and granulocyte-macrophage CSF (GM-CSF) receptors (IL-3R and GM-CSFR). By Northern blot analysis of mRNAs obtained from normal human blood eosinophils, we show in this report that the hematopoietic cytokines IL-5, IL-3, and GM-CSF down-regulate IL-5Rα mRNA while up-regulating α-chain mRNAs for both IL-3R and GM-CSFR as well as the β-chain mRNA. More detailed characterization reveals that the down-regulation of IL-5Rα mRNA is specific to IL-3, IL-5, and GM-CSF; occurs very rapidly (reaching maximum inhibition within 2 h); is cytokine dose dependent; and does not require protein synthesis. Nuclear run-on and mRNA stability experiments demonstrate that cytokine-induced inhibition of IL-5Rα mRNA accumulation occurs at the level of IL-5Rα gene transcription, whereas enhanced accumulation of mRNAs for IL-3Rα and the β-chain results from reduced mRNA degradation. We suggest from these experiments that in human blood eosinophils, IL-5Rα gene transcription and IL-5Rα mRNA metabolism can be regulated by mechanisms that are distinct from those used for IL-3Rα and GM-CSFRα.

Involvement of p59fynT in interleukin-5 receptor signaling

Previous studies implicate the nonreceptor protein tyrosine kinase (PTK) p59fyn in the propagation of signals from the B cell antigen receptor. To elucidate the functions of this kinase, we examined B cell responsiveness in mice engineered to lack the hematopoietic isoform of p59fyn. Remarkably, antigen receptor signaling was only modestly defective in fynTnull B cells. In contrast, signaling from the interleukin (IL)-5 receptor which ordinarily provides a comitogenic stimulus with antiimmunoglobulin, was completely blocked. Our results document the importance of p59fynT in IL-5 responses in B cells, and they support a general model for cytokine receptor signal transduction involving the simultaneous recruitment of at least three families of PTK.