Human recombinant interleukin 4 induces Fc epsilon receptors (CD23) on normal human B lymphocytes

Cytokine and chemokine profiles in women with endometriosis, polycystic ovary syndrome, and unexplained infertility

Numerous factors (including immunological, congenital, hormonal, and morphological disorders) can lead to infertility. In this regard, 3 specific diseases associated with infertility are discussed in this review study (i.e., polycystic ovary syndrome [PCOS], endometriosis [EMS], and unexplained infertility [UI]). PCOS is a common endocrine disorder characterized by chronic low-grade inflammation, and EMS is a benign disease characterized by the presence of ectopic endometrial tissue. UI refers to couples who are unable to conceive for no known reason. Conception and pregnancy are significantly affected by the immune system; in this regard, chemokines and cytokines play important roles in the regulation of immune responses. Patients with PCOS, EMS, and UI have altered cytokine and chemokine profiles, suggesting that dysregulation of these molecules may contribute to infertility in these conditions. Accordingly, the issue of infertility is addressed in this review study, a condition that affects approximately 16% of couples worldwide.

From neglect to spotlight: the underappreciated role of B cells in cutaneous inflammatory diseases

The skin, covering our entire body as its largest organ, manifests enormous complexities and a profound interplay of systemic and local responses. In this heterogeneous domain, B cells were considered strangers. Yet, recent studies have highlighted their existence in the skin and their distinct role in modulating cutaneous immunity across various immune contexts. Accumulating evidence is progressively shedding light on the significance of B cells in maintaining skin health and in skin disorders. Herein, we integrate current insights on the systemic and local contributions of B cells in three prevalent inflammatory skin conditions: Pemphigus Vulgaris (PV), Systemic Lupus Erythematosus (SLE), and Atopic Dermatitis (AD), underscoring the previously underappreciated importance of B cells within skin immunity. Moreover, we address the potential adverse effects of current treatments used for skin diseases, emphasizing their unintentional consequences on B cells. These comprehensive approaches may pave the way for innovative therapeutic strategies that effectively address the intricate nature of skin disorders.

Type 2-polarized memory B cells hold allergen-specific IgE memory

Allergen-specific immunoglobulin E (IgE) antibodies mediate pathology in diseases such as allergic rhinitis and food allergy. Memory B cells (MBCs) contribute to circulating IgE by regenerating IgE-producing plasma cells upon allergen encounter. Here, we report a population of type 2-polarized MBCs defined as CD23hi, IL-4Rαhi, and CD32low at both the transcriptional and surface protein levels. These MBC2s are enriched in IgG1- and IgG4-expressing cells while constitutively expressing germline transcripts for IgE. Allergen-specific B cells from patients with allergic rhinitis and food allergy were enriched in MBC2s. Furthermore, MBC2s generated allergen-specific IgE during sublingual immunotherapy, thereby identifying these cells as a major reservoir for IgE. The identification of MBC2s provides insights into the maintenance of IgE memory, which is detrimental in allergic diseases but could be beneficial in protection against venoms and helminths.

Engineering the IL-4/IL-13 axis for targeted immune modulation

The structurally and functionally related interleukin-4 (IL-4) and IL-13 cytokines play pivotal roles in shaping immune activity. The IL-4/IL-13 axis is best known for its critical role in T helper 2 (Th2) cell-mediated Type 2 inflammation, which protects the host from large multicellular pathogens, such as parasitic helminth worms, and regulates immune responses to allergens. In addition, IL-4 and IL-13 stimulate a wide range of innate and adaptive immune cells, as well as non-hematopoietic cells, to coordinate various functions, including immune regulation, antibody production, and fibrosis. Due to its importance for a broad spectrum of physiological activities, the IL-4/IL-13 network has been targeted through a variety of molecular engineering and synthetic biology approaches to modulate immune behavior and develop novel therapeutics. Here, we review ongoing efforts to manipulate the IL-4/IL-13 axis, including cytokine engineering strategies, formulation of fusion proteins, antagonist development, cell engineering approaches, and biosensor design. We discuss how these strategies have been employed to dissect IL-4 and IL-13 pathways, as well as to discover new immunotherapies targeting allergy, autoimmune diseases, and cancer. Looking ahead, emerging bioengineering tools promise to continue advancing fundamental understanding of IL-4/IL-13 biology and enabling researchers to exploit these insights to develop effective interventions.

Design of Glycoengineered IL-4 Antagonists Employing Chemical and Biosynthetic Glycosylation

Interleukin-4 (IL-4) plays a key role in atopic diseases. It coordinates T-helper cell differentiation to subtype 2, thereby directing defense toward humoral immunity. Together with Interleukin-13, IL-4 further induces immunoglobulin class switch to IgE. Antibodies of this type activate mast cells and basophilic and eosinophilic granulocytes, which release pro-inflammatory mediators accounting for the typical symptoms of atopic diseases. IL-4 and IL-13 are thus major targets for pharmaceutical intervention strategies to treat atopic diseases. Besides neutralizing antibodies against IL-4, IL-13, or its receptors, IL-4 antagonists can present valuable alternatives. Pitrakinra, an Escherichia coli-derived IL-4 antagonist, has been evaluated in clinical trials for asthma treatment in the past; however, deficits such as short serum lifetime and potential immunogenicity among others stopped further development. To overcome such deficits, PEGylation of therapeutically important proteins has been used to increase the lifetime and proteolytic stability. As an alternative, glycoengineering is an emerging strategy used to improve pharmacokinetics of protein therapeutics. In this study, we have established different strategies to attach glycan moieties to defined positions in IL-4. Different chemical attachment strategies employing thiol chemistry were used to attach a glucose molecule at amino acid position 121, thereby converting IL-4 into a highly effective antagonist. To enhance the proteolytic stability of this IL-4 antagonist, additional glycan structures were introduced by glycoengineering utilizing eucaryotic expression. IL-4 antagonists with a combination of chemical and biosynthetic glycoengineering could be useful as therapeutic alternatives to IL-4 neutralizing antibodies already used to treat atopic diseases.

Requirements of IL-4 during the Generation of B Cell Memory

IL-4 has long been established as a key regulator of Th cells and for promoting effective B cell survival and isotype class switching. Yet, despite having been extensively studied, the specific role of IL-4 in generating humoral memory in vivo is unclear. In this review, we explore the recent studies that unravel the cellular sources and spatiotemporal production of IL-4, the relationship between IL-4 and IL-21 during germinal center responses and the formation of Ab-secreting cells, and the current understanding of whether IL-4 promotes or suppresses memory B cell generation in vitro and in vivo.

IgG memory B cells expressing IL4R and FCER2 are associated with atopic diseases

BACKGROUND

Atopic diseases are characterized by IgE antibody responses that are dependent on cognate CD4 T cell help and T cell-produced IL-4 and IL-13. Current models of IgE cell differentiation point to the role of IgG memory B cells as precursors of pathogenic IgE plasma cells. The goal of this work was to identify intrinsic features of memory B cells that are associated with IgE production in atopic diseases.

METHODS

Peripheral blood B lymphocytes were collected from individuals with physician diagnosed asthma or atopic dermatitis (AD) and from non-atopic individuals. These samples were analyzed by spectral flow cytometry, single cell RNA sequencing (scRNAseq), and in vitro activation assays.

RESULTS

We identified a novel population of IgG memory B cells characterized by the expression of IL-4/IL-13 regulated genes FCER2/CD23, IL4R, IL13RA1, and IGHE, denoting a history of differentiation during type 2 immune responses. CD23+ IL4R+ IgG+ memory B cells had increased occurrence in individuals with atopic disease. Importantly, the frequency of CD23+ IL4R+ IgG+ memory B cells correlated with levels of circulating IgE. Consistently, in vitro stimulated B cells from atopic individuals generated more IgE+ cells than B cells from non-atopic subjects.

CONCLUSIONS

These findings suggest that CD23+ IL4R+ IgG+ memory B cells transcribing IGHE are potential precursors of IgE plasma cells and are linked to pathogenic IgE production.

The role of the Immune System in the Development of Endometriosis

Endometriosis is a chronic disease that affects about 10% of women of reproductive age. It can contribute to pelvic pain, infertility or other conditions such as asthma, cardiovascular disease, breast or ovarian cancer. Research has shown that one of the conditions for the development of endometrial lesions is the dysfunction of the immune system. It appears that immune cells, such as neutrophils, macrophages, NK cells and dendritic cells, may play a specific role in the angiogenesis, growth and invasion of endometriosis cells. Immune cells secrete cytokines and defensins that also affect the endometriosis environment. This review discusses the various components of the immune system that are involved in the formation of endometrial lesions in women.

Bidirectional Transport of IgE by CD23 in the Inner Ear of Patients with Meniere's Disease

Meniere's disease (MD) is a disorder of the inner ear characterized by episodes of spontaneous vertigo, fluctuating hearing loss, and tinnitus. Recent studies have demonstrated that IgE may play a role in the pathogenesis of MD. Patients with MD (n = 103), acoustic neuroma (n = 5), and healthy subjects (n = 72) were recruited into the study. Serum from the participants was analyzed for IgE and type 2-related cytokines. IgE and CD23 expression levels in vestibular end organs of patients, C57BL/6 mice, or mouse HEI-OC1 cells were analyzed. Finally, the role of CD23 in IgE transcytosis was assessed using HEI-OC1 cells. Serum IgE was elevated in patients with MD and positively correlated with clinical symptoms. IL-4, IL-5, IL-10, IL-13, and CD23 levels were increased in patients with MD compared with the control group. In the transcytosis assay, mouse IgE was found to be bidirectionally transported across the HEI-OC1 cell monolayer. Additionally, CD23 downregulation using a small interfering RNA approach significantly reduced the efficiency of IgE transcytosis, suggesting that IgE is transported by CD23. Furthermore, exposure to IL-4 increased CD23 expression and enhanced IgE transcytosis in the HEI-OC1 cells and primary vestibular end organs. Our study indicated that IgE may play a role in the pathophysiology of MD. In addition, CD23-mediated IgE transcytosis in the hair cells may play a critical role in initiating inflammation in the inner ear. Thus, reducing the level of IgE may be a potentially effective approach for MD treatment.

Follicular dendritic cells restrict interleukin-4 availability in germinal centers and foster memory B cell generation

B cells within germinal centers (GCs) enter cycles of antibody affinity maturation or exit the GC as memory cells or plasma cells. Here, we examined the contribution of interleukin (IL)-4 on B cell fate decisions in the GC. Single-cell RNA-sequencing identified a subset of light zone GC B cells expressing high IL-4 receptor-a (IL4Ra) and CD23 and lacking a Myc-associated signature. These cells could differentiate into pre-memory cells. B cell-specific deletion of IL4Ra or STAT6 favored the pre-memory cell trajectory, and provision of exogenous IL-4 in a wild-type context reduced pre-memory cell frequencies. IL-4 acted during antigen-specific interactions but also influenced bystander cells. Deletion of IL4Ra from follicular dendritic cells (FDCs) increased the availability of IL-4 in the GC, impaired the selection of affinity-matured B cells, and reduced memory cell generation. We propose that GC FDCs establish a niche that limits bystander IL-4 activity, focusing IL-4 action on B cells undergoing selection and enhancing memory cell differentiation.

IgE Activates Monocytes from Cancer Patients to Acquire a Pro-Inflammatory Phenotype

IgE contributes to host-protective functions in parasitic and bacterial infections, often by monocyte and macrophage recruitment. We previously reported that monocytes contribute to tumour antigen-specific IgE-mediated tumour growth restriction in rodent models. Here, we investigate the impact of IgE stimulation on monocyte response, cellular signalling, secretory and tumour killing functions. IgE cross-linking on human monocytes with polyclonal antibodies to mimic formation of immune complexes induced upregulation of co-stimulatory (CD40, CD80, CD86), and reduced expression of regulatory (CD163, CD206, MerTK) monocyte markers. Cross-linking and tumour antigen-specific IgE antibody-dependent cellular cytotoxicity (ADCC) of cancer cells by cancer patient-derived monocytes triggered release of pro-inflammatory mediators (TNFα, MCP-1, IL-10, CXCL-10, IL-1β, IL-6, IL-23). High intratumoural gene expression of these mediators was associated with favourable five-year overall survival in ovarian cancer. IgE cross-linking of trimeric FcεRI on monocytes stimulated the phosphorylation of intracellular protein kinases widely reported to be downstream of mast cell and basophil tetrameric FcεRI signalling. These included recently-identified FcεRI pathway kinases Fgr, STAT5, Yes and Lck, which we now associate with monocytes. Overall, anti-tumour IgE can potentiate pro-inflammatory signals, and prime tumour cell killing by human monocytes. These findings will inform the development of IgE monoclonal antibody therapies for cancer.

Challenges and Opportunities for Consistent Classification of Human B Cell and Plasma Cell Populations

The increasingly recognized role of different types of B cells and plasma cells in protective and pathogenic immune responses combined with technological advances have generated a plethora of information regarding the heterogeneity of this human immune compartment. Unfortunately, the lack of a consistent classification of human B cells also creates significant imprecision on the adjudication of different phenotypes to well-defined populations. Additional confusion in the field stems from: the use of non-discriminatory, overlapping markers to define some populations, the extrapolation of mouse concepts to humans, and the assignation of functional significance to populations often defined by insufficient surface markers. In this review, we shall discuss the current understanding of human B cell heterogeneity and define major parental populations and associated subsets while discussing their functional significance. We shall also identify current challenges and opportunities. It stands to reason that a unified approach will not only permit comparison of separate studies but also improve our ability to define deviations from normative values and to create a clean framework for the identification, functional significance, and disease association with new populations.

Interleukin-18 binding protein attenuates renal injury of adriamycin-induced mouse nephropathy

Nephrotic syndrome is one of the most common kidney diseases in children, most of which were caused by minimal change disease, which could be typically reversible with the use of corticosteroid therapy in steroid-sensitive nephrotic syndrome. At the same time, there still exist some side effects caused by drugs and steroid-resistant nephrotic syndrome. It's urgent to investigate more accurate treatment to improve the situation. In this study, we chose mice model by adriamycin to observe the effect of IL-18BP intervention. It was shown that (1) weak general conditions appeared after adriamycin administration; (2) Proteinuria showed up after adriamycin-administration and then decreased with IL-18 binding protein intervention; (3) the level of triglyceride, cholesterol, IL-18, IFN-γ, and TNF-α in the IL-18 binding protein intervening group were significantly lower than those in the adriamycin-minimal change disease MCD group (all P < 0.01), and the levels of serum total protein, albumin, and IL-4 were significantly higher than those in the adriamycin-minimal change disease MCD group (P < 0.05, P < 0.01, P < 0.05); (4) ultramicrostructural examination demonstrated wide fusion of foot processes of glomerular epithelial cells in adriamycin-minimal change disease MCD mice, while only focal fusion occurred in IL-18 binding protein intervening mice. In conclusion, IL-18BP repaired the proteinurine, histopathological injury of kidney, and the induction of serum cytokines in mice models of minimal change disease induced by adriamycin.

Dock10 regulates CD23 expression and sustains B-cell lymphopoiesis in secondary lymphoid tissue

Dock10, a guanine nucleotide exchange factor for the Rho GTPases Rac1 and Cdc42, affects cell morphology, membrane protrusive activity, and cell movement. Dock10 is prominently expressed in lymphoid tissue and upregulated by IL-4 in B cells. To investigate the physiological role of Dock10, WT mice and Dock10 KO mice were used. KO mice showed decreased numbers of B cells in spleen, both follicular B cells and marginal zone B cells, and in peripheral blood, but not in bone marrow. The antiapoptotic effect of IL-4 in vitro, the migratory response to CXCL13 or CCL21 in vitro, and the whole genome expression profile were intact in spleen B cells from KO mice. CD23, the low-affinity receptor for immunoglobulin E, was overexpressed on follicular B cells from KO mice, suggesting that Dock10 negatively regulates membrane CD23 expression. Negative regulation of CD23 expression by Dock10 could play a role in B cell maturation and function.

Strategies targeting the IL-4/IL-13 axes in disease

IL-4 and IL-13 are pleiotropic Th2 cytokines produced by a wide variety of different cell types and responsible for a broad range of biology and functions. Physiologically, Th2 cytokines are known to mediate host defense against parasites but they can also trigger disease if their activities are dysregulated. In this review we discuss the rationale for targeting the IL-4/IL-13 axes in asthma, atopic dermatitis, allergic rhinitis, COPD, cancer, inflammatory bowel disease, autoimmune disease and fibrotic disease as well as evaluating the associated clinical data derived from blocking IL-4, IL-13 or IL-4 and IL-13 together.

Interleukin-4 receptor signaling and its binding mechanism: A therapeutic insight from inhibitors tool box

Studies on Interlukin-4 (IL-4) disclosed great deal of information about its various physiological and pathological roles. All these roles depend upon its interaction and signaling through either type-I (IL-4Rα/common γ-chain) or type-II (IL-4Rα/IL-13Rα) receptors. Another cytokine, IL-13, shares some of the functions of IL-4, because both cytokines use a common receptor subunit, IL-4Rα. Here in this review, we discuss the structural details of IL-4 and IL-4Rα subunit and the structural similarities between IL-4 and IL-13. We also describe detailed chemistry of type-I and type-II receptor complexes and their signaling pathways. Furthermore, we elaborate the strength of type-II hetero dimer signals in response to IL-4 and IL-13. These cytokines are prime players in pathogenesis of allergic asthma, allergic hypersensitivity, different cancers, and HIV infection. Recent advances in the structural and binding chemistry of these cytokines various types of inhibitors were designed to block the interaction of IL-4 and IL-13 with their receptor, including several IL-4 mutant analogs and IL-4 antagonistic antibodies. Moreover, different targeted immunotoxins, which is a fusion of cytokine protein with a toxin or suicidal gene, are the new class of inhibitors to prevent cancer progression. In addition few small molecular inhibitors such as flavonoids have also been developed which are capable of binding with high affinity to IL-4Rα and, therefore, can be very effective in blocking IL-4-mediated responses.

Short-term subcutaneous grass pollen immunotherapy under the umbrella of anti-IL-4: A randomized controlled trial

BACKGROUND

Allergen immunotherapy is currently the only disease-modifying treatment available for allergic rhinitis and allergic asthma.

OBJECTIVES

We sought to evaluate the induction of sustained tolerance to allergen when anti-IL-4 was combined with a suboptimal course of grass pollen subcutaneous immunotherapy (SCIT) using the allergen-induced skin late-phase response (LPR) and exploratory immune monitoring as surrogate markers of therapeutic response.

METHODS

In this randomized, double-blind, 3-group parallel design trial, 37 participants with seasonal allergic rhinitis received suboptimal SCIT (30,000 standardized quality units) in combination with anti-IL-4 (VAK694) and suboptimal SCIT (30,000 standardized quality units) plus placebo antibody or double placebo (placebo SCIT and placebo antibody) restricted to 13 weeks before the grass pollen season. The primary end point was the size of the LPR at 12 months. Exploratory end points included measures of the immunomodulatory activity of treatment by using IL-4 and IL-10 FluoroSpot assays, flow cytometry of T cells, and measurement of IgE, IgG4, and facilitated antigen binding.

RESULTS

Both active treatment arms led to a substantial and sustained reduction of the LPR with no additional suppression with addition of anti-IL-4. Treatment with anti-IL-4 and SCIT compared with SCIT alone led to a sustained reduction in allergen-specific IL-4-producing cell counts (P < .01). Both active treatment arms led to induction of dual IL-4/IL-10-producing cells during the pollen season.

CONCLUSION

The combination of anti-IL-4 with SCIT provided no additional benefit over SCIT alone in suppressing the allergen-induced skin LPR. A larger trial is needed to assess whether the observed ex vivo downregulation of TH2 responses might translate into clinical benefit.

IL-4: an important cytokine in determining the fate of T cells

The pleiotropic effect of cytokines has been well documented, but the effects triggered by unique cytokines in different T cell types are still under investigation. The most relevant findings on the influence of interleukin-4 (IL-4) on T cell activation, differentiation, proliferation, and survival of different T cell types are discussed in this review. The main aim of our study was to correlate the observed effect with the corresponding molecular mechanism induced on IL-4/IL-4R interaction, in an effort to understand how the same extracellular stimuli can trigger a wide spectrum of signaling pathways leading to different responses in each T cell type.

Adrenergic regulation of IgE involves modulation of CD23 and ADAM10 expression on exosomes

Soluble CD23 plays a role in the positive regulation of an IgE response. Engagement of the β2 adrenergic receptor (β2AR) on a B cell is known to enhance the level of both soluble CD23 and IgE, although the mechanism by which this occurs is not completely understood. In this study, we report that, in comparison with a CD40 ligand/IL-4-primed murine B cell alone, β2AR engagement on a primed B cell increased gene expression of a disintegrin and metalloproteinase (ADAM)10, which is the primary sheddase of CD23, as well as protein expression of both CD23 and ADAM10, in a protein kinase A- and p38 MAPK-dependent manner, and promoted the localization of these proteins to exosomes as early as 2 d after priming, as determined by both Western blot and flow cytometry and confirmed by electron microscopy. In comparison with isolated exosomes released from primed B cells alone, the transfer of exosomes released from β2AR agonist-exposed primed B cells to cultures of recipient primed B cells resulted in an increase in the level of IgE produced per cell, without affecting the number of cells producing IgE, as determined by ELISPOT. These effects still occurred when a β2AR antagonist was added along with the transfer to block residual agonist, and they failed to occur when exosomes were isolated from β2AR-deficient B cells. These findings suggest that the mechanism responsible for mediating the β2AR-induced increase in IgE involves a shuttling of the β2AR-induced increase in CD23 and ADAM10 proteins to exosomes that subsequently mediate an increase in IgE.

Preclinical development of CAT-354, an IL-13 neutralizing antibody, for the treatment of severe uncontrolled asthma

BACKGROUND AND PURPOSE

IL-13 is a pleiotropic Th2 cytokine considered likely to play a pivotal role in asthma. Here we describe the preclinical in vitro and in vivo characterization of CAT-354, an IL-13-neutralizing IgG4 monoclonal antibody (mAb), currently in clinical development.

EXPERIMENTAL APPROACH

In vitro the potency, specificity and species selectivity of CAT-354 was assayed in TF-1 cells, human umbilical vein endothelial cells and HDLM-2 cells. The ability of CAT-354 to modulate disease-relevant mechanisms was tested in human cells measuring bronchial smooth muscle calcium flux induced by histamine, eotaxin generation by normal lung fibroblasts, CD23 upregulation in peripheral blood mononuclear cells and IgE production by B cells. In vivo CAT-354 was tested on human IL-13-induced air pouch inflammation in mice, ovalbumin-sensitization and challenge in IL-13 humanized mice and antigen challenge in cynomolgus monkeys.

KEY RESULTS

CAT-354 has a 165 pM affinity for human IL-13 and functionally neutralized human, human variant associated with asthma and atopy (R130Q) and cynomolgus monkey, but not mouse, IL-13. CAT-354 did not neutralize human IL-4. In vitro CAT-354 functionally inhibited IL-13-induced eotaxin production, an analogue of smooth muscle airways hyperresponsiveness, CD23 upregulation and IgE production. In vivo in humanized mouse and cynomolgus monkey antigen challenge models CAT-354 inhibited airways hyperresponsiveness and bronchoalveolar lavage eosinophilia.

CONCLUSIONS AND IMPLICATIONS

CAT-354 is a potent and selective IL-13-neutralizing IgG4 mAb. The preclinical data presented here support the trialling of this mAb in patients with moderate to severe uncontrolled asthma.

Deficient CCR7 signaling promotes TH2 polarization and B-cell activation in vivo

The chemokine receptor CCR7 has a central role in regulating homing and positioning of T cells and DCs to lymph nodes (LNs) and participates in T-cell development and activation. In this study, we addressed the role of CCR7 signaling in T(H) 2 polarization and B-cell activation. We provide evidence that the lack of CCR7 drives the capacity of naïve CD4(+) T cells to polarize toward T(H) 2 cells. This propensity contributes to a lymph node environment in CCR7-deficent mice characterized by increased expression of IL-4 and increased frequency of T(H) 2 cells. We show that elevated IL-4 levels lead to B-cell activation characterized by up-regulated expression of MHC class II, CD23 and CD86. Activated B cells are in turn highly efficient in presenting antigen to CD4(+) T cells and thus potentially contribute to the T(H) 2 microenvironment. Taken together, our results support the idea of a CCR7-dependent patterning of T(H) 2 responses, with absent CCR7 signaling favoring T(H) 2 polarization, dislocation of T helper cells into the B-cell follicles and, as a consequence, B-cell activation.

Interleukins, from 1 to 37, and interferon-γ: receptors, functions, and roles in diseases

Advancing our understanding of mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections could lead to effective and targeted therapies. Subsets of immune and inflammatory cells interact via ILs and IFNs; reciprocal regulation and counter balance among T(h) and regulatory T cells, as well as subsets of B cells, offer opportunities for immune interventions. Here, we review current knowledge about ILs 1 to 37 and IFN-γ. Our understanding of the effects of ILs has greatly increased since the discoveries of monocyte IL (called IL-1) and lymphocyte IL (called IL-2); more than 40 cytokines are now designated as ILs. Studies of transgenic or knockout mice with altered expression of these cytokines or their receptors and analyses of mutations and polymorphisms in human genes that encode these products have provided important information about IL and IFN functions. We discuss their signaling pathways, cellular sources, targets, roles in immune regulation and cellular networks, roles in allergy and asthma, and roles in defense against infections.

CD23-dependent transcytosis of IgE and immune complex across the polarized human respiratory epithelial cells

IgE-mediated allergic inflammation occurs when allergens cross-link IgE on the surface of immune cells, thereby triggering the release of inflammatory mediators as well as enhancing Ag presentations. IgE is frequently present in airway secretions, and its level can be enhanced in human patients with allergic rhinitis and bronchial asthma. However, it remains completely unknown how IgE appears in the airway secretions. In this study, we show that CD23 (FcεRII) is constitutively expressed in established or primary human airway epithelial cells, and its expression is significantly upregulated when airway epithelial cells were subjected to IL-4 stimulation. In a transcytosis assay, human IgE or IgE-derived immune complex (IC) was transported across a polarized Calu-3 monolayer. Exposure of the Calu-3 monolayer to IL-4 stimulation also enhanced the transcytosis of either human IgE or the IC. A CD23-specific Ab or soluble CD23 significantly reduced the efficiency of IgE or IC transcytosis, suggesting a specific receptor-mediated transport by CD23. Transcytosis of both IgE and the IC was further verified in primary human airway epithelial cell monolayers. Furthermore, the transcytosed Ag-IgE complexes were competent in inducing degranulation of the cultured human mast cells. Because airway epithelial cells are the first cell layer to come into contact with inhaled allergens, our study implies CD23-mediated IgE transcytosis in human airway epithelial cells may play a critical role in initiating and contributing to the perpetuation of airway allergic inflammation.

Counter-regulation mechanism of IL-4 and IFN-α signal transduction through cytosolic retention of the pY-STAT6:pY-STAT2:p48 complex

IFN-α and IL-4 induce Th1 and Th2 responses, respectively, and often display antagonistic actions against each other. To elucidate the molecular mechanism of counter-regulation, we have investigated the signal interception by IFN-α and IL-4, employing a human B-cell line Ramos, sensitive to both cytokines. In these cells, IFN-α effectively inhibited IL-4-induced Fc epsilon receptor II (CD23) expression, whereas IL-4 suppressed IFN-α-mediated IRF7 expression. The counter-regulatory action by IL-4 and IFN-α proceeded with a delayed kinetics requiring 4 h. Notably, IFN-α did not affect the IL-4-induced tyrosine phosphorylation of STAT6, but induced a time-dependent cytoplasmic accumulation of phosphotyrosine(pY)-STAT6 and a corresponding decrease in nuclear pY-STAT6. By confocal analysis and co-immunoprecipitation assays, we demonstrated the colocalization and molecular interaction of IL-4-induced pY-STAT6 with IFN-α-induced pY-STAT2:p48 in the cytosol. In addition, the over-expression of STAT2 or STAT6 induced the concomitant cytosolic accumulation of pY-STAT6 or pY-STAT2, leading to the suppression of IL-4-induced CD23 or IFN-α-induced IRF7 gene expression, respectively. Our data suggest that the signals ensued by IFN-α and IL-4 induce cytoplasmic sequestration of IL-4-activated STAT6 and IFN-α-activated STAT2:p48 in B cells through the formation of pY-STAT6:pY-STAT2:p48 complex, which provides a novel mechanism by which IFN-α and IL-4 cross-regulate their signaling into the nucleus.

CD23/FcεRII: molecular multi-tasking

CD23 is the low-affinity receptor for immunoglobulin (Ig)E and plays important roles in the regulation of IgE responses. CD23 can be cleaved from cell surfaces to yield a range of soluble CD23 (sCD23) proteins that have pleiotropic cytokine-like activities. The regions of CD23 responsible for interaction with many of its known ligands, including IgE, CD21, major histocompatibility complex (MHC) class II and integrins, have been identified and help to explain the structure-function relationships within the CD23 protein. Translational studies of CD23 underline its credibility as a target for therapeutic intervention strategies and illustrate its involvement in mediating therapeutic effects of antibodies directed at other targets.

Diversifying selection and functional analysis of interleukin-4 suggests antagonism-driven evolution at receptor-binding interfaces

Background

Interleukin-4 (IL4) is a secreted immunoregulatory cytokine critically involved in host protection from parasitic helminths [1]. Reasoning that helminths may have evolved mechanisms to antagonize IL4 to maximize their dispersal, we explored mammalian IL4 evolution.

Results

This analysis revealed evidence of diversifying selection at 15 residues, clustered in epitopes responsible for IL4 binding to its Type I and Type II receptors. Such a striking signature of selective pressure suggested either recurrent episodes of pathogen antagonism or ligand/receptor co-evolution. To test the latter possibility, we performed detailed functional analysis of IL4 allotypes expressed by Mus musculus musculus and Mus musculus castaneus, which happen to differ at 5 residues (including three at positively selected sites) in and adjacent to the site 1 epitope that binds the IL4Rα subunit shared by the Type I and Type II IL4 receptors. We show that this intra-species variation affects the ability of IL4 neither to bind IL4 receptor alpha (IL4Rα) nor to signal biological responses through its Type I receptor.

Conclusions

Our results -- reminiscent of clustered positively selected sites revealing functionally important residues at host-virus interaction interfaces -- are consistent with IL4 having evolved to avoid recurrent pathogen antagonism, while maintaining the capacity to bind and signal through its cognate receptor. This work exposes what may be a general feature of evolutionary conflicts fought by pathogen antagonists at host protein-protein interaction interfaces involved in immune signaling: the emergence of receptor-binding ligand epitopes capable of buffering amino acid variation.

Mast cells modulate transport of CD23/IgE/antigen complex across human intestinal epithelial barrier

BACKGROUND

Food allergy and chronic intestinal inflammation are common in western countries. The complex of antigen/IgE is taken up into the body from the gut lumen with the aid of epithelial cell-derived CD23 (low affinity IgE receptor II) that plays an important role in the pathogenesis of intestinal allergy. This study aimed to elucidate the role of mast cell on modulation of antigen/IgE complex transport across intestinal epithelial barrier.

METHODS

Human intestinal epithelial cell line HT29 cell monolayer was used as a study platform. Transepithelial electric resistance (TER) and permeability to ovalbumin (OVA) were used as the markers of intestinal epithelial barrier function that were recorded in response to the stimulation of mast cell-derived chemical mediators.

RESULTS

Conditioned media from naïve mast cell line HMC-1 cells or monocyte cell line THP-1 cells significantly upregulated the expression of CD23 and increased the antigen transport across the epithelium. Treatment with stem cell factor (SCF), nerve growth factor (NGF), retinoic acid (RA) or dimethyl sulphoxide (DMSO) enhanced CD23 expression in HT29 cells. Conditioned media from SCF, NGF or RA-treated HMC-1 cells, and SCF, NGF, DMSO or RA-treated THP-1 cells enhanced immune complex transport via enhancing the expression of the CD23 in HT29 cells and the release of inflammatory mediator TNF-α. Nuclear factor kappa B inhibitor, tryptase and TNF-α inhibited the increase in CD23 in HT29 cells and prevents the enhancement of epithelial barrier permeability.

CONCLUSIONS

Mast cells play an important role in modulating the intestinal CD23 expression and the transport of antigen/IgE/CD23 complex across epithelial barrier. (Tu YH, Oluwole C, Struiksma S, Perdue MH, Yang PC. Mast cells modulate transport of CD23/IgE/antigen complex across human intestinal epithelial barrier.

Allergen extract-induced interleukin-10 in human memory B cells inhibits immunoglobulin E production

BACKGROUND

Elevated specific IgE antibody levels are common in atopic individuals, caused by T-helper type 2-dominated B cell activation. The induction of antigen-specific IL-10 secreting T cells is discussed as an important mechanism during specific immunotherapy. By contrast the presence and function of B cell-derived IL-10 is not well defined yet.

OBJECTIVE

We investigated whether type-I allergen extracts induce IL-10 expression in human B cells and analysed its functional role on IgE production.

METHODS

Human peripheral B cells were stimulated with grass pollen, house dust mite (HDM) (Dermatophagoides pteronyssimus; Der p) and dog allergen extract. Expression of IL-10 by activated human B cells was determined by flow cytometric analysis and ELISA. Functional analysis considering immunoglobulin production was assayed by ELISA.

RESULTS

The allergen extracts studied induced IL-10 expression in B cells. However, the ability to induce IL-10 differed between the allergen extracts. The most potent allergen extract was dog (169+/-28 pg/mL), followed by grass pollen (141+/-10 pg/mL) and HDM allergen (125+/-11 pg/mL). Upon allergen extract stimulation only CD27 expressing memory B cells produced IL-10 and co-expressed the very early activation antigen CD69. The addition of allergen extracts to B cells activated by anti-CD40 and IL-4 selectively inhibited IgE which was dependent on allergen extract-induced IL-10. By contrast the other immunoglobulin subclasses like IgA, IgG or IgM were not altered upon allergen extract challenge.

CONCLUSION

Our data indicate that allergen-activated memory B cells can modulate IgE production through secretion of IL-10.

STAT3 is required for IL-21–induced secretion of IgE from human naive B cells

The production of immunoglobulin E (IgE) is tightly regulated. This is evidenced by the fact that it comprises less than 0.0001% of serum Ig, and aberrant production causes atopic conditions, including allergy, rhinitis, and anaphylaxis. Interleukin-4 (IL-4) is a well-characterized inducer of IgE by human and murine B cells, whereas interferon-γ can antagonize this effect. IL-21 has also been recognized for its ability to suppress IL-4–induced IgE production by murine B cells. Here, we identified IL-21 as an inducer of IgE production by CD40L-stimulated human naive B cells. Furthermore, there was a striking synergy between IL-4 and IL-21 on inducing IgE secretion by CD40L-stimulated human B cells, such that the levels detected under these conditions exceeded those induced by IL-4 or IL-21 alone by more than 10-fold. IL-21 induced activation of STAT3 and analysis of B cells from patients with loss-of-function STAT3 mutations revealed that the ability of IL-21 to induce IgE secretion, and augment that driven by IL-4, was STAT3-dependent. These findings highlight a fundamental difference between the regulation of IgE production by human and murine B cells and have implications for the dysregulated production of IgE in conditions characterized by extremely high levels of serum IgE.

Low affinity IgE receptors: regulation and functional roles in cell activation

The low affinity IgE receptors (Fc epsilon RII/CD23) homologous to animal lectins have the unique property of cleaving-off the extracytoplasmic portion as the soluble form (IgE binding factor; IgE-BF). Molecular analysis using Fc epsilon RII/CD23 cDNA proved that Fc epsilon RII is not unique to B lymphocytes but is expressed on a variety of cell lineages including T lymphocytes, macrophages and eosinophils. In these cell types, IL-4 is a general inducer of this molecule while IFN-gamma down-regulates B cell Fc epsilon RII/CD23 and up-regulates Fc epsilon RII/CD23 on macrophage and eosinophil cell lines. As predicted by the expression of Fc epsilon RII/CD23 in some HTLV-1(+) T cell lines, Fc epsilon RII/CD23 proved to be induced on normal peripheral T lymphocytes by IL-4 or IL-2 in the presence of additional permissive signals. As indicated by IL-2-dependent Fc epsilon RII/CD23 induction, there is an interesting bilateral co-regulation between Fc epsilon RII/CD23 and the 55 kDa chain of the IL-2 receptor complex with Tac antigen (IL-2R/p55(Tac]. Triggering of Fc epsilon RII/CD23 resulted in the enhanced expression of IL-2R/p55(Tac), whereas IL-2 enhanced the expression of Fc epsilon RII/CD23 in some systems. It is suggested that the triggering of cell surface Fc epsilon RII/CD23 by natural ligands is effectively buffered by soluble Fc epsilon RII/CD23 (IgE-BF).

A possible association of Staphylococcus enterotoxin B-induced asthma and sinusitis

In order to gain insight into a possible association between chronic sinusitis and asthma, 85 patients with sinusitis and asthma underwent functional endoscopic sinus surgical treatment and serum antibodies and cytokines were measured. The results showed that 51 out of 85 patients with high serum anti Staphylococcus enterotoxin B (SEB) antibody before treatment obtained satisfactory results for both sinusitis and asthma. The high level of Th2 cytokine IL-4 was down regulated to the levels of normal controls after sinus surgery. Thirty-four out of 85 patients did not show high serum anti-SEB antibody before sinus surgery and did not show much improvement in their asthmatic symptoms although sinusitis symptoms were resolved by sinus surgery. It was concluded that bacterial superantigen SEB (in the sinuses) might play a crucial role in the pathogenesis of lower airway hypersensitivity.

c-Rel plays a key role in deficient activation of B cells from a non-X-linked hyper-IgM patient

Our previous results demonstrated that B cells from a patient (pt1) with non-X-linked hyper-IgM syndrome (HIGM) possess an atypical CD23(lo) phenotype that is unaffected by CD40-mediated activation. To investigate the molecular mechanism underlying defective CD23 expression in pt1 B cells, we used lymphoblastoid cell lines that express LMP1 under the control of a tetracycline-inducible promoter (LCL(tet)). Our analysis revealed that the CD23(lo) phenotype in the pt1-LCL(tet) cells is a direct consequence of diminished CD23 transcription. We demonstrate a marked decrease in c-Rel-containing complexes that bind to the proximal CD23a/b promoters in pt1-LCL(tet) extracts, resulting from an overall lower expression of c-Rel in pt1-LCL(tet) cells. Analysis of c-Rel mRNA revealed relatively equal amounts in pt1-LCL(tet) and control LCL(tet) cells, indicating that diminished c-Rel protein expression is unrelated to decreased transcription. Finally, a critical role for c-Rel in CD23 regulation was demonstrated by effectively altering c-Rel expression that resulted in the direct modulation of CD23 surface expression. Collectively, these findings demonstrate that low levels of c-Rel are the underlying cause of aberrant CD23 expression in pt1 B cells and are likely to play a critical role in the pathophysiology of this form of HIGM.

Sjögren's syndrome in the NOD mouse model is an interleukin-4 time-dependent, antibody isotype-specific autoimmune disease

NOD.B10-H2b and NOD/LtJ mice manifest many features of primary and secondary Sjögren's syndrome (SjS), respectively, an autoimmune disease affecting primarily the salivary and lacrimal glands leading to xerostomia (dry mouth) and xerophthalmia (dry eyes). A previous study suggested that the T(H2) cytokine, interleukin (IL)-4, plays an integral role in the development and onset of SjS-like disease in the NOD mouse model. To define further the role of IL-4 in onset of murine SjS-like disease, we have examined two IL4 gene knockout (KO) mouse strains, NOD.IL4-/- and NOD.B10-H2b.IL4-/-. Unlike NOD.IL4-/- mice, NOD.B10-H2b.IL4-/- mice are resistant to development of diabetes. The presence of a dysfunctional IL4 gene did not impede leukocyte infiltration of the salivary glands, yet prevented development of secretory dysfunction. Whereas NOD.B10-H2b.IL4-/- mice exhibited many pathophysiological manifestations of SjS-like disease common to the parental strains, these mice failed to produce anti-muscarinic acetylcholine type-3 receptor (M3R) autoantibodies of the IgG1 isotype. Cytokine mRNA expression profiles and adoptive transfers of T lymphocytes from NOD.B10-H2b.Gfp mice into NOD.B10-H2b.IL4-/- mice at different ages suggest IL-4 is required during the pre-clinical disease stage (around 12 weeks of age) to initiate clinical xerostomia. The results of this study indicate that the failure of NOD.IL4-/- and NOD.B10-H2b.IL4-/- mice to synthesize anti-M3R autoantibodies of the IgG1 isotype apparently explains why these mice fail to develop exocrine gland dysfunction, despite exhibiting pre-clinical manifestations of SjS-like disease.

CD23-mediated IgE transport across human intestinal epithelium: inhibition by blocking sites of translation or binding

BACKGROUND & AIMS

In previous studies in rodent models of food allergy, we identified that sensitization induces expression of CD23 on intestinal epithelial cells and results in enhanced IgE-dependent transepithelial antigen uptake; further studies in CD23-/- mice provided evidence that CD23 is involved in protected transport of antigen into the body. Little information exists in humans on receptor-mediated immunoglobulin (Ig)E transport across epithelia. The present study was designed to examine expression of CD23 by human epithelial cells, determine its isoform and regulation by interleukin (IL) 4, and identify the role of CD23 in transepithelial IgE transport.

METHODS

Epithelial expression of CD23 was studied in cell lines, ileal biopsy specimens, and explanted fetal intestine. Bidirectional transport of IgE was measured across filter-grown cells, either normal cells or those transfected with antisense CD23 oligonucleotides, or in the presence of blocking antibody.

RESULTS

Expression of the low-affinity IgE receptor was demonstrated in cultured epithelial cells as well as in situ cells in human intestine. CD23b was the isoform expressed by HT29, T84, and Caco-2 cells. IL-4 up-regulated the expression of epithelial CD23. IgE was transported in both the basal-to-apical direction and the apical-to-basal direction across filter-grown epithelial cells, a process that was inhibited by transfection of cells with CD23 antisense oligonucleotides or pretreatment with nonspecific IgE or anti-CD23 antibody.

CONCLUSIONS

These findings provide evidence that CD23 encodes a functional IgE receptor on human intestinal epithelial cells and that this epithelial receptor is likely to play an important role in food allergies.

Inhibitory activity of a ceramide library on interleukin-4 production from activated T cells

Allergic diseases are hypersensitivity disorders associated with the production of specific immunoglobulin E (IgE) to environmental allergens. Interleukin (IL)-4, produced primarily by CD4(+) T cells, is an important stimulus for the switch of the antibody isotype to IgE in both mice and humans. In this study we investigated the inhibitory activity of IL-4 production in activated T cells by screening ceramide derivatives prepared by solid phase combinatorial chemistry. Many ceramide derivatives significantly inhibited IL-4 production in T cells. In particular, ceramide derivatives with a lauroyl group showed strong inhibitory activities on IL-4 production in both phorbol 12-myristate 13-acetate (PMA)-activated EL4 T cells and antigen-primed cells, suggesting that they can be used as compounds for the development of anti-allergic agents.

Elevated expression of CD23 on peripheral blood B lymphocytes from patients with bullous pemphigoid: correlation with increased serum IgE

BACKGROUND

Increased serum IgE levels are occasionally found in patients with severe bullous pemphigoid (BP). CD23, a low affinity Fc receptor for IgE, is mainly expressed on mature B lymphocytes. Studies have suggested that serum levels of soluble CD23 (sCD23) correlate with serum IgE levels and disease severity in BP.

OBJECTIVE

The purpose of our study is to examine whether the expression of CD23 is elevated in BP and whether this expression correlates with serum IgE levels and disease severity.

METHODS

We measured CD23 expression on B cells from patients with active BP, pemphigus vulgaris, pemphigus foliaceus, and atopic dermatitis (AD), as well as healthy control subjects, using a flow cytometer. Serum levels of IgE and sCD23 were also measured.

RESULTS

The expression of CD23 was significantly higher in BP patients compared with healthy control subjects (P < 0.05), whereas the levels were normal in the other bullous diseases. CD23 expression tended to be higher in severe BP compared with moderate BP, and the levels in severe BP were comparable to the levels in AD. Furthermore, CD23 expression correlated positively with serum IgE levels (P < 0.002), and the IgE levels were significantly higher in severe BP than in moderate BP (P < 0.01 ). CD23 expression in BP did not correlate with sCD23 levels.

CONCLUSIONS

These results suggest that the up-regulated surface CD23 on B cells may be involved in IgE synthesis and inflammatory events in BP.

Isolation of high-affinity human IgE and IgG antibodies recognising Bet v 1 and Humicola lanuginosa lipase from combinatorial phage libraries

Allergen-specific Fab fragments isolated from combinatorial IgE and IgG libraries are useful tools for studying allergen-antibody interactions. To characterise the interaction between different allergens and antibodies we have created recombinant human phage antibody libraries in the Fab format. Human IgE and IgG libraries have been created from patients allergic to birch pollen or lipase. These libraries have been used to select binders recognising the major birch pollen allergen Bet v 1 and Humicola lanuginosa lipase. A panel of allergen-specific IgE and IgG antibodies were identified; these were further characterised by allergen binding studies using Biacore and competition studies using human sera and antibodies purified from human sera. Affinities in the nM range were recorded and a competition with human sera for allergen binding was observed.

Allergen-mediated modulation of CD23 expression is interferon-γ and interleukin-10 dependent in allergic and non-allergic individuals

BACKGROUND

CD23 plays an important role in IgE regulation. The modulation of CD23 expression during specific immunotherapy (SIT) has been described previously. In the present study, we investigated in detail the effects of complete birch pollen allergen extract (BPA) on CD23 expression of peripheral blood mononuclear cells (PBMCs) in vitro.

METHODS

PBMCs from 14 birch pollen-allergic (bp-allergic) patients and eight non-bp-allergic controls were stimulated with IL-4 and increasing doses of BPA. CD23 expression on monocytes and B cells was measured by flow cytometry; sCD23 release and the levels of IFN-gamma and IL-10 secretion were determined by ELISA. To analyse the mechanisms on CD23 expression in more detail, neutralizing anti-IFN-gamma and anti-IL-10 antibodies were added to IL-4 and BPA-stimulated cultures.

RESULTS

IL-4 induced CD23 expression on B cells and on monocytes and sCD23 release in the bp-allergic and non-bp-allergic groups. The addition of BPA to IL-4-stimulated PBMC decreased CD23 expression significantly and dose-dependently on B cells in both groups. CD23 expression on monocytes was also decreased in both groups after the addition of BPA, but higher doses were required in the non-bp-allergic population. IL-4-induced sCD23 release was also significantly decreased after the addition of BPA. IFN-gamma and IL-10 were induced by BPA in both the bp-allergic and non-bp-allergic groups. The addition of neutralizing anti-IFN-gamma antibodies increased CD23 expression on B cells, which were stimulated with IL-4 and BPA, but had no effect on monocytes, whereas the addition of anti-IL-10 antibodies increased CD23 expression on monocytes but not on B cells.

CONCLUSION

These data indicate that early immunological effects like down-regulation of CD23 on B cells and monocytes, which are observed during SIT are dose dependent, mediated by IFN-gamma and IL-10 and seem not to depend per se on the sensitization state of an individual.

Mitochondrial adenine nucleotide translocator 3 is regulated by IL-4 and IFN-γ via STAT-dependent pathways

IL-4 and IFN-gamma are prototypical Th2 and Th1 cytokines, respectively. They reciprocally regulate a number of genes involved in Th1 vs Th2 immune balance. Using DD-PCR analysis, adenine nucleotide translocase (ANT) 3, an enzyme which exchanges ATP and ADP through mitochondrial membrane, has been identified as a novel target counter-regulated by IL-4 and IFN-gamma. We have observed that IL-4 and IFN-gamma each up-regulates ANT3 in T cells both at mRNA and protein levels, while cotreatment of IL-4 and IFN-gamma counter-regulates ANT3 expression. In contrast, other isoforms of ANT were not affected by IL-4 or IFN-gamma. Emplyoing transfection and overexpression of STAT6 and STAT1 in STAT-deficient cells, we demonstrate that induction of ANT3 by IL-4 and IFN-gamma proceeds via pathways involving STAT6 and STAT1, respectively. Furthermore, regulation of ANT3 expression by IL-4 and IFN-gamma correlated with the modulation T cell survival by these cytokines from dex-induced apoptosis. Considering the critical role of mitochondrial ANTs in energy metabolism and apoptosis, ANT3 regulation by IL-4 and IFN-gamma may have a functional implication in cytokine-mediated T cell survival.

Overexpression of interleukin-4 in lungs of mice impairs elimination of Histoplasma capsulatum

Protection against the pathogenic fungus Histoplasma capsulatum requires Th1 cytokines. Since interleukin-4 (IL-4) can inhibit both Th1 cytokine production and activity, we examined the effects of overproduction of IL-4 in the lung on the course of pulmonary histoplasmosis. IL-4 lung transgenic mice manifested a higher fungal burden in their lungs, but not spleens, compared to wild-type infected controls. Despite the higher burden, the transgenic animals were ultimately capable of controlling infection. The adverse effects of IL-4 on H. capsulatum elimination were not observed during the early phase of infection (days 1 to 3) but were maximal at day 7 postinfection, prior to the induction of cell-mediated immunity. Analysis of total body and lung cytokine levels revealed that gamma interferon and tumor necrosis factor alpha production were not inhibited in the presence of excess IL-4. Our results with transgenic mice were supported by additional in vivo studies in which allergen induction of pulmonary IL-4 was associated with delayed clearance of H. capsulatum yeast and increased fungal burden. These findings demonstrate that excess production of endogenous IL-4 modulates protective immunity to H. capsulatum by delaying clearance of the organism but does not prevent the generation of a Th1 response that ultimately controls infection.

Effects of low concentrations of cadmium on immunoglobulin E production by human B lymphocytes in vitro

Exposure to cadmium (Cd) can cause a variety of biological effects including alterations of immune responses in animals and humans. Both immunosuppression and immunoenhancement have been reported. The present study was aimed at investigating the consequences of exposure to Cd on the human immunoglobulin (Ig) E synthesis, using purified peripheral blood B lymphocytes and IL-4 and anti-human CD40 monoclonal antibody (a-CD40 mAb) as stimuli. Low concentrations of Cd (0.1-10 microM) markedly inhibited production of IgE in a concentration-dependent manner. IgG production, in contrast to IgE, showed a tendency towards being enhanced by Cd, although with a certain individual variability; IgM production was not affected. Cd failed to alter immediate surface expression of the activation markers CD69 and CD23 indicating that early activation events were not impaired. However, the portion of activated B cells was diminished by Cd after stimulation for more than 24 h, paralleled by a concomitant decrease in viability and a subsequent reduction in proliferation. These data suggest that the mechanism of Cd action on activated B cells involved pathways that interrupted an effectively initiated cell activation and induced a cytotoxic signal. Results from this study thus provide further evidence for and new information on the immunotoxic and immunomodulatory effects of Cd on human immune responses.

Changes in TH1/TH2 immunity after endovascular and conventional infrarenal aortic aneurysm repair: its relevance for clinical practice

OBJECTIVE

to evaluate local surgical trauma induced by endovascular (TPEG) and conventional infrarenal aortic aneurysm repair (AAA-C), the inflammatory response and changes in cell-mediated and antibody-mediated immunity as illustrated by the type-1/type-2 T-helper (TH1/TH2) cell balance were investigated.

DESIGN

prospective study.

PATIENTS AND METHODS

sixteen patients were included, eight patients underwent AAA-C and eight TPEG. Venous peripheral blood samples were collected 24h preoperatively and 24, 48, 72h, 5 and 7 days postoperatively. Besides the WBC, intracellular TH1/TH2 cytokines (IFN-gamma/IL-4) and the cell surface markers HLA-DR on monocytes and CD23 on B cells were measured by four colour flow cytometry.

RESULTS

statistically significant higher values in the AAA-C group were demonstrated for neutrophiles. The TH1/TH2 immunobalance (expressed by forming the ratio of IFN-(gamma/IL-4 producing T cells as well as by the ratio of HLA-DR(pos) monocytes/CD23(pos) B-cells) showed a significant shift towards TH2 immunity in the AAA-C group whereas TPEG led to a significant lesser shift 24-72h after surgery (p < 0.05).

CONCLUSIONS

TPEG leads to a minor distortion of the TH1/TH2 immunobalance. This implies that TPEG is a less stressing procedure, that is especially beneficial in patients whose conditions are considered less suitable for AAA-C due to age and serious comorbidity.

The CD23b promoter is a target for NF-AT transcription factors in B-CLL cells

CD23 is atypically highly expressed in various chronic diseases, including B-CLL, lupus erythematodes and rheumatoid arthritis. Its expression can be further enhanced by interleukin 4 (IL-4). We have shown before that in B-CLL cells nuclear factor(s) of activated T cells (NF-ATs) show permanent nuclear localization and therefore constitutive transcriptional activity. Here we identify CD23b promoter as a novel target for NF-AT factors in B-CLL cells. The CD23b promoter contains two NF-AT binding sites to which NF-ATp and NF-ATc factors bind with high affinity. Mutations introduced into these sites abolished NF-AT binding and impaired the promoter activity, as did cyclosporin A (CsA), an inhibitor of nuclear transport of NF-ATs. Furthermore, we show that IL-4-induced transcription factor STAT6 cooperates with NF-ATs in the induction of the CD23b promoter activity. These results show that the CD23b promoter is a target for NF-AT factors and suggest that the cooperation between NF-AT and STAT factors might be one of the molecular mechanisms responsible for high-level expression of CD23 on the surface of B-CLL cells.