Nerve growth factor or IL-3 induces more IL-13 production from basophils of allergic subjects than from basophils of nonallergic subjects

Neurotrophins: Neuroimmune Interactions in Human Atopic Diseases

Allergic diseases are accompanied by a variety of symptoms such as pruritus, coughing, sneezing, and watery eyes, which can result in severe physiological and even psychological impairments. The exact mechanisms of these conditions are not yet completely understood. However, recent studies demonstrated a high relevance of neurotrophins in allergic inflammation, as they induce cytokine release, mediate interaction between immune cells and neurons, and exhibit different expression levels in health and disease. In this review, we aim to give an overview of the current state of knowledge concerning the role of neurotrophins in atopic disorders such as atopic dermatitis, allergic asthma, and allergic rhinitis.

Basophils from allergy to cancer

Human basophils, first identified over 140 years ago, account for just 0.5-1% of circulating leukocytes. While this scarcity long hampered basophil studies, innovations during the past 30 years, beginning with their isolation and more recently in the development of mouse models, have markedly advanced our understanding of these cells. Although dissimilarities between human and mouse basophils persist, the overall findings highlight the growing importance of these cells in health and disease. Indeed, studies continue to support basophils as key participants in IgE-mediated reactions, where they infiltrate inflammatory lesions, release pro-inflammatory mediators (histamine, leukotriene C₄: LTC₄) and regulatory cytokines (IL-4, IL-13) central to the pathogenesis of allergic diseases. Studies now report basophils infiltrating various human cancers where they play diverse roles, either promoting or hampering tumorigenesis. Likewise, this activity bears remarkable similarity to the mounting evidence that basophils facilitate wound healing. In fact, both activities appear linked to the capacity of basophils to secrete IL-4/IL-13, with these cytokines polarizing macrophages toward the M2 phenotype. Basophils also secrete several angiogenic factors (vascular endothelial growth factor: VEGF-A, amphiregulin) consistent with these activities. In this review, we feature these newfound properties with the goal of unraveling the increasing importance of basophils in these diverse pathobiological processes.

Involvement of Neuro-Immune Interactions in Pruritus With Special Focus on Receptor Expressions

Pruritus is a common, but very challenging symptom with a wide diversity of underlying causes like dermatological, systemic, neurological and psychiatric diseases. In dermatology, pruritus is the most frequent symptom both in its acute and chronic form (over 6 weeks in duration). Treatment of chronic pruritus often remains challenging. Affected patients who suffer from moderate to severe pruritus have a significantly reduced quality of life. The underlying physiology of pruritus is very complex, involving a diverse network of components in the skin including resident cells such as keratinocytes and sensory neurons as well as transiently infiltrating cells such as certain immune cells. Previous research has established that there is a significant crosstalk among the stratum corneum, nerve fibers and various immune cells, such as keratinocytes, T cells, basophils, eosinophils and mast cells. In this regard, interactions between receptors on cutaneous and spinal neurons or on different immune cells play an important role in the processing of signals which are important for the transmission of pruritus. In this review, we discuss the role of various receptors involved in pruritus and inflammation, such as TRPV1 and TRPA1, IL-31RA and OSMR, TSLPR, PAR-2, NK1R, H1R and H4R, MRGPRs as well as TrkA, with a focus on interaction between nerve fibers and different immune cells. Emerging evidence shows that neuro-immune interactions play a pivotal role in mediating pruritus-associated inflammatory skin diseases such as atopic dermatitis, psoriasis or chronic spontaneous urticaria. Targeting these bidirectional neuro-immune interactions and the involved pruritus-specific receptors is likely to contribute to novel insights into the underlying pathogenesis and targeted treatment options of pruritus.

Construction and analysis for dys-regulated lncRNAs and mRNAs in LPS-induced porcine PBMCs

Long non-coding RNAs (lncRNAs) are emerging as key regulators in inflammation. However, their functions and profiles in LPS-induced inflammation in pigs are largely unknown. In this study, we profiled global lncRNA and mRNA expression changes in PBMCs treated with LPS using the lncRNA-seq technique. In total 43 differentially expressed (DE) lncRNAs and 1082 DE mRNAs were identified in porcine PBMCs after LPS stimulation. Functional enrichment analysis on DE mRNAs indicated these genes were involved in inflammation-related signaling pathways, including cytokine–cytokine receptor interaction, TNF-α, NF-κB, Jak-STAT and TLR signaling pathways. In addition, co-expression network and function analysis identified the potential lncRNAs related to inflammatory response and immune response. The expressions of eight lncRNAs (ENSSSCT00000045208, ENSSSCT00000051636, ENSSSCT00000049770, ENSSSCT00000050966, ENSSSCT00000047491, ENSSSCT00000049750, ENSSSCT00000054262 and ENSSSCT00000044651) were validated in the LPS-treated PBMCs by quantitative real-time PCR (qRT-PCR). In LPS-challenged piglets, we identified that expression of three lncRNAs (ENSSSCT00000051636, ENSSSCT00000049770, and ENSSSCT00000047491) was significantly up-regulated in liver, spleen and jejunum tissues after LPS challenge, which indicated that these lncRNAs might be important regulators for inflammation. This study provides the first lncRNA and mRNA transcriptomic landscape of LPS-mediated changes in porcine PBMCs, which might provide potential insights into lncRNAs involved in regulating inflammation in pigs.

Is There a Role for Basophils in Cancer?

Basophils were identified in human peripheral blood by Paul Ehrlich over 140 years ago. Human basophils represent <1% of peripheral blood leukocytes. During the last decades, basophils have been described also in mice, guinea pigs, rabbits, and monkeys. There are many similarities, but also several immunological differences between human and mouse basophils. There are currently several strains of mice with profound constitutive or inducible basophil deficiency useful to prove that these cells have specific roles in vivo. However, none of these mice are solely and completely devoid of all basophils. Therefore, the relevance of these findings to humans remains to be established. It has been known for some time that basophils have the propensity to migrate into the site of inflammation. Recent observations indicate that tissue resident basophils contribute to lung development and locally promote M2 polarization of macrophages. Moreover, there is increasing evidence that lung-resident basophils exhibit a specific phenotype, different from circulating basophils. Activated human and mouse basophils synthesize restricted and distinct profiles of cytokines. Human basophils produce several canonical (e.g., VEGFs, angiopoietin 1) and non-canonical (i.e., cysteinyl leukotriene C₄) angiogenic factors. Activated human and mouse basophils release extracellular DNA traps that may have multiple effects in cancer. Hyperresponsiveness of basophils has been demonstrated in patients with JAK2^V617F-positive polycythemia vera. Basophils are present in the immune landscape of human lung adenocarcinoma and pancreatic cancer and can promote inflammation-driven skin tumor growth. The few studies conducted thus far using different models of basophil-deficient mice have provided informative results on the roles of these cells in tumorigenesis. Much more remains to be discovered before we unravel the hitherto mysterious roles of basophils in human and experimental cancers.

Human mast cells and basophils-How are they similar how are they different?

Mast cells and basophils are key contributors to allergies and other inflammatory diseases since they are the most prominent source of histamine as well as numerous additional inflammatory mediators which drive inflammatory responses. However, a closer understanding of their precise roles in allergies and other pathological conditions has been marred by the considerable heterogeneity that these cells display, not only between mast cells and basophils themselves but also across different tissue locations and species. While both cell types share the ability to rapidly degranulate and release histamine following high-affinity IgE receptor cross-linking, they differ markedly in their ability to either react to other stimuli, generate inflammatory eicosanoids or release immunomodulating cytokines and chemokines. Furthermore, these cells display considerable pharmacological heterogeneity which has stifled attempts to develop more effective anti-allergic therapies. Mast cell- and basophil-specific transcriptional profiling, at rest and after activation by innate and adaptive stimuli, may help to unravel the degree to which these cells differ and facilitate a clearer understanding of their biological functions and how these could be targeted by new therapies.

Possible roles of basophils in chronic itch

Basophils are blood granulocytes and normally constitute <1% of blood peripheral leucocytes. Basophils share some morphological and functional similarities with mast cells, and basophils were once regarded as redundant and negligible circulating mast cells. However, recent studies reveal the indispensable roles of basophils in various diseases, including allergic and pruritic diseases. Basophils may be involved in itch through the mediation of a Th2 immune response, interaction with other cells in the skin and secretion of a wide variety of itch-related mediators, for example histamine, cytokines and chemokines (IL-4, IL-13, IL-31 and TSLP), proteases (cathepsin S), prostaglandins (PGE2 and PGD2), substance P and platelet-activating factor. Not only pruritic skin diseases (eg, atopic dermatitis, irritant contact dermatitis, chronic urticaria, prurigo, papulo-erythroderma of Ofuji, eosinophilic pustular folliculitis, scabies, tick bites and bullous pemphigoid) but also pruritic systemic diseases (eg, primary sclerosing cholangitis and polycythemia vera) may be affected by basophils.

Neutralization of nerve growth factor (NGF) inhibits the Th2 response and protects against the respiratory syncytial virus (RSV) infection

Increasing evidence suggests that respiratory syncytial virus (RSV) infection during the early life is an important risk factor for the development of asthma. RSV infection is associated with neurogenic inflammation in the airways along with the increased expression of nerve growth factor (NGF). However, the role of NGF in RSV infection is not clear. In this study, we infected the rat with RSV and treated these animals with anti-NGF neutralization antibody. We found that anti-NGF treatment significantly alleviated the lung inflammation as evidenced by decreased inflammatory infiltration and decreased airway resistance. Importantly, anti-NGF treatment resulted in increased Th1, but decreased Th2 immune responses, and facilitated the viral control in the tissues and blood. Therefore, NGF inhibited Th2 but increased Th1 responses in RSV infection. Pharmacological intervention of NGF signaling during severe RSV infections could prevent or decrease further asthma symptoms.

NGF and Its Receptors in the Regulation of Inflammatory Response

There is growing interest in the complex relationship between the nervous and immune systems and how its alteration can affect homeostasis and result in the development of inflammatory diseases. A key mediator in cross-talk between the two systems is nerve growth factor (NGF), which can influence both neuronal cell function and immune cell activity. The up-regulation of NGF described in inflamed tissues of many diseases can regulate innervation and neuronal activity of peripheral neurons, inducing the release of immune-active neuropeptides and neurotransmitters, but can also directly influence innate and adaptive immune responses. Expression of the NGF receptors tropomyosin receptor kinase A (TrkA) and p75 neurotrophin receptor (p75NTR) is dynamically regulated in immune cells, suggesting a varying requirement for NGF depending on their state of differentiation and functional activity. NGF has a variety of effects that can be either pro-inflammatory or anti-inflammatory. This apparent contradiction can be explained by considering NGF as part of an endogenous mechanism that, while activating immune responses, also activates pathways necessary to dampen the inflammatory response and limit tissue damage. Decreases in TrkA expression, such as that recently demonstrated in immune cells of arthritis patients, might prevent the activation by NGF of regulatory feed-back mechanisms, thus contributing to the development and maintenance of chronic inflammation.

The Evolution of Human Basophil Biology from Neglect towards Understanding of Their Immune Functions

Being discovered long ago basophils have been neglected for more than a century. During the past decade evidence emerged that basophils share features of innate and adaptive immunity. Nowadays, basophils are best known for their striking effector role in the allergic reaction. They hence have been used for establishing new diagnostic tests and therapeutic approaches and for characterizing natural and recombinant allergens as well as hypoallergens, which display lower or diminished IgE-binding activity. However, it was a long way from discovery in 1879 until identification of their function in hypersensitivity reactions, including adverse drug reactions. Starting with a historical background, this review highlights the modern view on basophil biology.

Role of Nerve Growth Factor in Development and Persistence of Experimental Pulmonary Hypertension

RATIONALE

Pulmonary hypertension (PH) is characterized by a progressive elevation in mean pulmonary arterial pressure, often leading to right ventricular failure and death. Growth factors play significant roles in the pathogenesis of PH, and their targeting may therefore offer novel therapeutic strategies in this disease.

OBJECTIVES

To evaluate the nerve growth factor (NGF) as a potential new target in PH.

METHODS

Expression and/or activation of NGF and its receptors were evaluated in rat experimental PH induced by chronic hypoxia or monocrotaline and in human PH (idiopathic or associated with chronic obstructive pulmonary disease). Effects of exogenous NGF were evaluated ex vivo on pulmonary arterial inflammation and contraction, and in vitro on pulmonary vascular cell proliferation, migration, and cytokine secretion. Effects of NGF inhibition were evaluated in vivo with anti-NGF blocking antibodies administered both in rat chronic hypoxia- and monocrotaline-induced PH.

MEASUREMENTS AND MAIN RESULTS

Our results show increased expression of NGF and/or increased expression/activation of its receptors in experimental and human PH. Ex vivo/in vitro, we found out that NGF promotes pulmonary vascular cell proliferation and migration, pulmonary arterial hyperreactivity, and secretion of proinflammatory cytokines. In vivo, we demonstrated that anti-NGF blocking antibodies prevent and reverse PH in rats through significant reduction of pulmonary arterial inflammation, hyperreactivity, and remodeling.

CONCLUSIONS

This study highlights the critical role of NGF in PH. Because of the recent development of anti-NGF blocking antibodies as a possible new pain treatment, such a therapeutic strategy of NGF inhibition may be of interest in PH.

Neurotrophic tyrosine kinase receptor 1 is a direct transcriptional and epigenetic target of IL-13 involved in allergic inflammation

Although interleukin (IL)-13 and neurotrophins are functionally important for the pathogenesis of immune responses, the interaction of these pathways has not been explored. Herein, by interrogating IL-13-induced responses in human epithelial cells we show that neurotrophic tyrosine kinase receptor, type 1 (NTRK1), a cognate, high-affinity receptor for nerve growth factor (NGF), is an early transcriptional IL-13 target. Induction of NTRK1 was accompanied by accumulation of activating epigenetic marks in the promoter; transcriptional and epigenetic changes were signal transducer and activator of transcription 6 dependent. Using eosinophilic esophagitis as a model for human allergic inflammation, we found that NTRK1 was increased in inflamed tissue and dynamically expressed as a function of disease activity and that the downstream mediator of NTRK1 signaling early growth response 1 protein was elevated in allergic inflammatory tissue compared with control tissue. Unlike NTRK1, its ligand NGF was constitutively expressed in control and disease states, indicating that IL-13-stimulated NTRK1 induction is a limiting factor in pathway activation. In epithelial cells, NGF and IL-13 synergistically induced several target genes, including chemokine (C-C motif) ligand 26 (eotaxin-3). In summary, we have demonstrated that IL-13 confers epithelial cell responsiveness to NGF by regulating NTRK1 levels by a transcriptional and epigenetic mechanism and that this process likely contributes to allergic inflammation.

Basophils as Key Regulators of Allergic Inflammation and Th2-type Immunity

Basophils have long been suspected as playing more than a bystander role in initiating and maintaining allergic disorders, despite their relatively low numbers compared with other effector cells, such as mast cells and eosinophils. In vitro studies clearly demonstrated their propensity to generate proallergic cytokines, such as interleukin 4 and interleukin 13, as well as histamine and leukotrienes after simulation with allergens and innate IgE-dependent triggers. However, only very recently have mouse basophils been identified as key regulators of allergy in vivo, including orchestrating Th2 immunity to protease allergens in the induction phase. This review highlights these exciting advances that go far in unraveling our understanding of basophil function in the orchestration of allergic inflammation.

Nerve growth factor: from the early discoveries to the potential clinical use

The physiological role of the neurotrophin nerve growth factor (NGF) has been characterized, since its discovery in the 1950s, first in the sensory and autonomic nervous system, then in central nervous, endocrine and immune systems. NGF plays its trophic role both during development and in adulthood, ensuring the maintenance of phenotypic and functional characteristic of several populations of neurons as well as immune cells. From a translational standpoint, the action of NGF on cholinergic neurons of the basal forebrain and on sensory neurons in dorsal root ganglia first gained researcher's attention, in view of possible clinical use in Alzheimer's disease patients and in peripheral neuropathies respectively. The translational and clinical research on NGF have, since then, enlarged the spectrum of diseases that could benefit from NGF treatment, at the same time highlighting possible limitations in the use of the neurotrophin as a drug. In this review we give a comprehensive account for almost all of the clinical trials attempted until now by using NGF. A perspective on future development for translational research on NGF is also discussed, in view of recent proposals for innovative delivery strategies and/or for additional pathologies to be treated, such as ocular and skin diseases, gliomas, traumatic brain injuries, vascular and immune diseases.

Artemin causes hypersensitivity to warm sensation, mimicking warmth-provoked pruritus in atopic dermatitis

BACKGROUND

Itch impairs the quality of life for many patients with dermatoses, especially atopic dermatitis (AD), and is frequently induced by a warm environment.

OBJECTIVE

To determine the mechanism underlying itch induction by warmth, we focused on artemin, a member of glial cell line-derived neurotrophic factors (GDNFs).

METHODS

A gene array assay revealed that artemin was expressed in substance P-treated dermal fibroblasts. The expression of artemin in healthy and AD-lesional skin was evaluated with immunohistochemistry and in situ hybridization. The impact of fibroblast-derived artemin on the proliferation and morphology of neural cell was investigated in vitro. To confirm the involvement of artemin in skin sensibility, wild-type and GDNF family receptor α3 knockout mice were employed for sensory examination.

RESULTS

Artemin-expressing fibroblasts accumulated in skin lesions of patients with AD. Artemin induced cell proliferation of a neuroblastoma cell line in vitro, and intradermal injection of artemin in mice resulted in peripheral nerve sprouting and thermal hyperalgesia. Artemin-treated mice demonstrated scratching behavior in a warm environment, but mice deficient for GDNF family receptor α3, a potent artemin receptor, did not show this behavior. Furthermore, the escaping response to heat stimulus was attenuated in GDNF family receptor α3 knockout mice, suggesting that artemin may contribute to sensitivity to heat.

CONCLUSION

These data suggest that dermal fibroblasts secrete artemin in response to substance P, leading to abnormal peripheral innvervation and thermal hyperalgesia. We hypothesize that artemin lowers the threshold of temperature-dependent itch sensation and might therefore be a novel therapeutic target for treating pruritic skin disorders, including AD.

Cellular immune response parameters that influence IgE sensitization

In vitro basophil responses have long been used in mechanistic studies to help assess the human allergic diathesis, particularly during therapeutic intervention. Recent evidence points to the use of dendritic cells (DCs) in also being valuable in evaluating therapies aimed at lessening disease through immunomodulation. This review article therefore takes a look at some of the recent advances in old and new assays employing both basophils and DCs, with the added perception that the responses mediated by two cell types are insightful towards understanding immune cell mechanisms underlying allergic disease.

Basophils: emerging roles in the pathogenesis of allergic disease

After approximately 130 years since their discovery as rare granulocytes that circulate in blood, basophils are just now gaining respect as significant contributors in the pathogenesis underlying allergic inflammation and disease. While long known for secreting preformed and newly synthesized mediators and for selectively infiltrating tissue during immunoglobulin E (IgE)-mediated inflammation, their role has largely been viewed as redundant to that of tissue mast cells in functioning as effector cells. This line of thought has persisted even though it has been known in humans for approximately 20 years that basophils additionally produce relatively large quantities of cytokines, e.g. interleukin-4 (IL-4)/IL-13, that are central for the manifestations of allergic disease. Studies using novel IL-4 reporter mice have significantly added to the in vivo importance of basophils as IL-4 producing cells, with recent findings indicating that these cells also function as antigen-presenting cells essential in initiating T-helper 2 responses. If confirmed and translated to humans, these provocative findings will give new meaning to the role basophils have in allergic disease, and in immunology overall.

Allergic agonists in apheresis platelet products are associated with allergic transfusion reactions

BACKGROUND

The mechanisms that underlie allergic transfusion reactions (ATRs) are not well characterized, but likely involve recipient, donor, and product factors. To assess product factors associated with ATRs, we investigated candidate mediators in apheresis platelet (PLT) products associated with ATRs and controls.

STUDY DESIGN AND METHODS

Using bead-based and standard enzyme-linked immunosorbent assays, we tested supernatants from 20 consecutive apheresis PLT transfusions associated with ATRs and 30 control products for concentrations of mediators in three categories: acute inflammatory mediators, direct agonists of basophils and mast cells, and growth and/or priming factors of basophils and mast cells.

RESULTS

Median concentrations of the direct allergic agonists C5a, brain-derived neurotrophic factor (BDNF), and CCL5 (RANTES) were 16.6, 41.8, and 13.9% higher, respectively, in the supernatant of apheresis PLT products that were most strongly associated with ATRs (p < 0.05 for each mediator). Other direct agonists (macrophage inflammatory protein-1α, monocyte chemotactic protein-1, eotaxin-1, interleukin-8) were similar between groups. Concentrations of acute inflammatory mediators and basophil growth and/or priming factors were also similar between groups (p > 0.2 for all associations).

CONCLUSION

The allergic agonists C5a, BDNF, and CCL5 may be mediators of ATRs in apheresis PLT products. Acute inflammatory proteins and basophil and/or mast cell growth and priming factors do not appear to be associated with apheresis PLT products that cause ATRs.

Induction of IL-13 production and upregulation of gene expression of protease activated receptors in P815 cells by IL-6

Interleukin (IL)-6 is a multifunctional cytokine which has been showed to induce up-regulated expression of Fc epsilon RI receptor and histamine production in mast cells. However, little is known of its effects on Th2 cytokine secretion and protease activated receptor (PAR) expression in mast cells. In the present study, we examined potential influence of IL-6 on IL-13, IL-4 and IL-10 release from P815 cells and PAR expression on P815 cells by using flow cytometry analysis, quantitative real-time PCR, ELISA and cellular activation of signaling ELISA (CASE) techniques. The results showed that IL-6 induced up to 1.8-fold increase in IL-13, but not IL-4 or IL-10 release from P815 cells, and FSLLRY-NH(2) did not affect IL-6 induced IL-13 release. Tryptase elicited 2.0-fold increase in IL-13 release from P815 cells, which can be inhibited by IL-6. IL-6 elicited the up-regulated expression of PAR-1, PAR-2, PAR-3 and PAR-4 mRNAs, but had little effects on expression of PAR proteins. U0126, PD98059 and LY204002 abolished IL-6 induced IL-13 release when they were preincubated with P815 cells, indicating ERK and Akt cell signaling pathways may be involved in the event. In conclusion, IL-6 can stimulate IL-13 release from mast cells through an ERK and Akt cell signaling pathway dependent, but PAR independent mechanism.

Pulmonary allergic responses augment interleukin-13 secretion by circulating basophils yet suppress interferon-alpha from plasmacytoid dendritic cells

BACKGROUND

Allergic inflammatory processes may have the capacity to propagate systemically through the actions of circulating leucocytes. Consequently, basophils from allergic individuals are often 'primed', as evidenced by their hyperresponsiveness in vitro. IFN-alpha secreted predominantly by plasmacytoid dendritic cells (pDCs), suppresses basophil priming for IL-13 production in vitro.

OBJECTIVE

This study sought in vivo correlates arising during experimental allergen challenge that support an 'axis-interplay' between basophils and pDCs.

METHODS

Using segmental allergen challenge (SAC) in the lung, the immune responses of both cell types from the blood were investigated in volunteers (n=10) before and 24 h after allergen exposure. These responses were then correlated with inflammatory parameters measured in bronchoalveolar lavage fluids (BALF).

RESULTS

In the blood, SAC significantly augmented IL-13 secretion by basophils induced by IL-3 (P=0.009), yet reduced IFN-alpha secreted by pDCs stimulated with CpG (P=0.018). Both parameters were negatively correlated (P=0.0015), at least among those subjects that secreted the latter. Circulating basophil IL-13 responses further correlated with post-SAC bronchoalveolar lavage (BAL) parameters including IL-13 protein (P=0.04), basophil (P=0.051), eosinophil (P=0.0018), and total cell counts (P<0.003). Basophil and IL-13 levels in BAL correlated likewise (P=0.0002).

CONCLUSIONS

These results support a mechanism of immune regulation whereby an allergen reduces innate immune responses and IFN-alpha production by pDCs, resulting in an enhanced inflammation and basophil cytokine production at sites of allergen exposure.

Human basophils secrete IL-3: evidence of autocrine priming for phenotypic and functional responses in allergic disease

Although IL-3 is commonly recognized for its growth factor-like activity, in vitro studies have long demonstrated a unique capacity for this cytokine to also augment the proinflammatory properties and phenotype of human basophils. In particular, basophils secrete mediators that are hallmarks in allergic disease, including vasoactive amines (e.g., histamine), lipid metabolites (e.g., leukotriene C(4)), and cytokines (e.g., IL-4/IL-13), which are all markedly enhanced with IL-3 pretreatment. This priming phenomenon is observed in response to both IgE-dependent and IgE-independent stimulation. Additionally, IL-3 directly activates basophils for IL-13 secretion and enhanced CD69 expression, two markers that are elevated in allergic subjects. Lymphocytes are commonly thought to be the source of the IL-3 that primes for these basophil responses. However, we demonstrate herein for the first time that basophils themselves rapidly produce IL-3 (within 4 h) in response to IgE-dependent activation. More importantly, our findings definitively show that basophils rapidly bind and utilize the IL-3 they produce, as evidenced by functional and phenotypic activity that is inhibited in the presence of neutralizing anti-IL-3 receptor (CD123) Abs. We predict that autocrine IL-3 activity resulting from low-level IgE/FcepsilonRI cross-linking by specific allergen represents an important mechanism behind the hyperreactive nature of basophils that has long been observed in allergic disease.

Human IgE+ and IgE- are not equivalent to mouse highly cytokinergic IgE

BACKGROUND

We have previously defined IgE+ as the IgE on basophils from a subset of highly allergic asthmatic subjects that release histamine after stimulation with histamine-releasing factor (HRF). The mechanism of IgE+ remains an enigma. Recently, there have been reports of monomeric highly cytokinergic IgEs causing mediator release, cytokine release, and phosphorylation events in cultured rodent and human mast cells in the absence of antigen.

OBJECTIVE

We investigated whether human IgE+ might exist as highly cytokinergic IgE in the human system.

METHODS

IgE+ was defined as causing greater than 10% histamine release by using HRF as a stimulus of human basophils. By definition, IgE- did not support histamine release to HRF. Once defined, serum and various purified human IgEs were used to stimulate purified human basophils or cultured human mast cells. The cells were examined for histamine release, extracellular signal-regulated kinase (ERK) phosphorylation, and IL-13 secretion.

RESULTS

We found that neither IgE+ nor IgE- induced ERK phosphorylation, histamine release, and IL-13 release from freshly isolated basophils in the absence of a specific antigen. However, human IgE alone did stimulate ERK phosphorylation in cultured human mast cells and IL-3-primed human basophils.

CONCLUSION

Human IgE+ is not an equivalent of the mouse highly cytokinergic IgE. However, human IgE did have effects on cultured mast cells and basophils. The effect of highly cytokinergic IgE on ERK phosphorylation and cytokine secretion might be due to the priming effect of human basophils and mast cells.

Distinct characteristics of signal transduction events by histamine-releasing factor/translationally controlled tumor protein (HRF/TCTP)-induced priming and activation of human basophils

We previously identified a negative correlation between histamine release to histamine releasing factor/translationally controlled tumor protein (HRF/TCTP) and protein levels of the Src homology 2 domain-containing inositol 5' phosphatase (SHIP) in basophils. We have also demonstrated that HRF/TCTP primes basophils to release mediators. The purpose of this study was to begin characterization of signal transduction events directly induced by HRF/TCTP and to investigate these events when HRF/TCTP is used as a priming agent for human basophil histamine release. Highly purified human basophils were examined for surface expression of bound HRF/TCTP, changes in calcium, and phosphorylation of Akt, mitogen-activated protein kinase kinase (MEK), extracellular signal-regulated kinase (ERK), Syk, and FcepsilonRIgamma. Results showed that basophils from all donors bound HRF/TCTP. There was a biphasic calcium response to HRF/TCTP, which corresponded to the magnitude of histamine release. Furthermore, those donors who have direct histamine release when exposed to HRF/TCTP (HRF/TCTP responder [HRF/TCTP-R] donors) have phosphorylation of Syk, Akt, MEK, and ERK. Remarkably, basophils from HRF/TCTP-nonresponder (HRF/TCTP-NR) donors do not show phosphorylation of these molecules. This finding is different from IL-3, which also primes basophils for histamine release, but does show phosphorylation of these events. We conclude that priming induced by HRF/TCTP is distinct from that induced by IL-3.

Determination of serum interleukin-13 and nerve growth factor in patients with systemic lupus erythematosus and clinical significance

The changes in the levels of serum interleukin-13 (IL-13) and nerve growth factor (NGF) in patients with systemic lupus erythematosus (SLE) and their clinical significance were investigated. Sandwich ELISA was used to determine the levels of serum IL-13 and NGF in 35 SLE patients and 15 normal controls. The results showed that the levels of serum IL-13 (92.69+/-9.87 pg/ml) and NGF (339.69+/-25.60 pg/ml) in active SLE patients were significantly higher than those in inactive SLE patients (IL-13, 54.22+/-9.31 pg/ml; NGF, 300.89+/-33.51 pg/ml) (P<0.01). The inactive patients also had significantly increased serum levels of IL-13 and NGF as compared with normal controls (IL-13, 35.20+/-12.70 pg/ml; NGF, 111.40+/-32.54 pg/ml; P<0.05 and P<0.01, respectively). Spearman correlation analysis revealed that the serum IL-13 levels were correlated with disease activity index of SLE (SLEDAI), ESR and serum levels of C3 (r= 0. 813, 0.504, -0.605, respectively). The serum NGF levels were also correlated with above markers (r=0.442, 0.338, -0.463, respectively). The serum levels of IL-13 and NGF had a positive correlation (r=0.506, P<0.01). It was suggested that IL-13 and NGF might be involved in the pathogenesis of SLE and closely correlated with disease activity.

The nerve growth factor and its receptors in airway inflammatory diseases

The nerve growth factor (NGF) belongs to the neurotrophin family and induces its effects through activation of 2 distinct receptor types: the tropomyosin-related kinase A (TrkA) receptor, carrying an intrinsic tyrosine kinase activity in its intracellular domain, and the receptor p75 for neurotrophins (p75NTR), belonging to the death receptor family. Through activation of its TrkA receptor, NGF activates signalling pathways, including phospholipase Cgamma (PLCgamma), phosphatidyl-inositol 3-kinase (PI3K), the small G protein Ras, and mitogen-activated protein kinases (MAPK). Through its p75NTR receptor, NGF activates proapoptotic signalling pathways including the MAPK c-Jun N-terminal kinase (JNK), ceramides, and the small G protein Rac, but also activates pathways promoting cell survival through the transcription factor nuclear factor-kappaB (NF-kappaB). NGF was first described by Rita Levi-Montalcini and collaborators as an important factor involved in nerve differentiation and survival. Another role for NGF has since been established in inflammation, in particular of the airways, with increased NGF levels in chronic inflammatory diseases. In this review, we will first describe NGF structure and synthesis and NGF receptors and their signalling pathways. We will then provide information about NGF in the airways, describing its expression and regulation, as well as pointing out its potential role in inflammation, hyperresponsiveness, and remodelling process observed in airway inflammatory diseases, in particular in asthma.

Evaluation of basophil activation in food allergy: present and future applications

PURPOSE OF REVIEW

The diagnosis of immediate hypersensitivity relies on specific IgE and history. Because of low specificity, however, provocation challenges are often necessary. Furthermore, IgE testing does not predict features such as reaction severity; nor can it discriminate cross-reactivity from multiple sensitizations. Direct and passive basophil activation tests may address these needs. In addition, measuring basophil activation ex vivo may be useful for monitoring patients with food allergies.

RECENT FINDINGS

Several papers using basophil activation tests demonstrate comparable sensitivity and specificity to current testing for food allergy. Flow-based basophil activation tests have also been used to assess functional characteristics of patient IgE. Finally, several activation phenotypes have been identified as markers of allergic inflammation in vivo; these phenotypes appear to correspond to earlier reports of spontaneous histamine-releasing basophils in patients with active allergic inflammation.

SUMMARY

Although in their early stages, direct basophil activation tests may prove to be useful in the clinic. Indirect basophil activation studies are useful when applied to compare functional aspects of IgE. Identification of basophil activation ex vivo is a promising approach for monitoring allergic inflammation.

Significant correlation between the CD63 assay and the histamine release assay in chronic urticaria

BACKGROUND

Antibodies directed to the alpha subunit of the high affinity IgE receptor and the IgE molecule are proposed to be of pathogenetic relevance in a group of patients with chronic urticaria (CU). The diagnosis of autoimmune chronic urticaria (ACU) is difficult; the autologous serum skin test (ASST) seems to be a useful screening test, but reliable, additional confirmatory methods are needed.

OBJECTIVES

To assess the diagnostic value of a modified serum-induced basophil activation test, the CD63 expression assay, in the diagnosis of ACU by comparing the results of the CD63 assay with the results of the histamine release (HR) test, the ASST and serum levels of soluble CD40 ligand (sCD40L).

METHODS

Using basophils from an atopic (DA) and a nonatopic (DNA) donor the activity of sera of 72 patients with CU were measured in HR assay by enzyme-linked immunosorbent assay and in CD63 expression assay by flow cytometry. An ASST was carried out in all patients; in 30 of the 72 patients sCD40L was detected and correlations were derived between the different assays. Sera of 20 normal controls and 26 patients with systemic autoimmune diseases were also tested in the HR assay and in the CD63 expression assay.

RESULTS

Histamine-releasing activity was detected in the sera of 51% (DA) and 32% (DNA) of CU patients and 57% (DA) and 28% (DNA) of sera upregulated CD63 expression on the surface of basophils from the different donors. There was a significant correlation between the HR and the CD63 assays carried out on both donors, but the ASST showed a strong correlation with the HR assay only for basophils from the DA. The serum level of sCD40L was significantly higher in patients with CU compared with controls, but the difference between the autoimmune and the nonautoimmune groups was not significant.

CONCLUSIONS

The CD63 expression assay seems to be a reliable functional test in the diagnosis of ACU, particularly if highly sensitive donor basophils are used, but the determination of the sCD40L serum level was not sufficient to differentiate between the autoimmune and the nonautoimmune patient groups.

Nerve growth factor: the central hub in the development of allergic asthma?

Neurotrophins like nerve growth factor (NGF), originally described as nerve growth factors in neuronal development, have been implicated in many physiological processes in the last years. They are now regarded as important factors involved in the resolution of pathological conditions. NGF has profound effects on inflammation, repair and remodeling of tissues. However, in the lung these beneficial effects can transact into disease promoting actions, e.g., in allergic inflammation or respiratory syncytial virus (RSV) infection. Overproduction of NGF then enhances inflammation, and promotes (neuronal) airway hyperreactivity and neurogenic inflammation. We hypothesize that NGF overexpression in certain vulnerable time windows during infancy could be a major risk factor for the development of asthma symptoms.

Interleukin-18 primes human basophilic KU812 cells for higher leukotriene synthesis

The human basophilic cell line KU812 that is an established tool for studying the function of human basophils, is differentiated into mature basophils by interleukin (IL-3) or other agents. However, whether leukotrienes (LTs)-synthesis is affected by cytokines in KU812 cells remains unknown. KU812 cells were incubated with IL-3, IL-4, IL-6, IL-13 or IL-18 for up to 14 days. The A23187 stimulated- and IgE cross-linked-synthesis of LTC(4) and LTB(4) were measured using an enzyme immunoassay (EIA). The expression of messenger RNA (mRNA) for LT-synthesizing enzymes was examined by reverse transcriptase polymerase chain reaction (RT-PCR), and the expression of 5-lipoxygenase (5-LO) was examined by immunostaining. Incubation with IL-3 (10 ng/ml) and IL-18 (10 ng/ml) induced the expression of 5-LO. A23187stimulated LT-synthesis and IgE cross-linked LT-synthesis were enhanced after incubation with IL-3 or IL-18. These results indicated that IL-3 and IL-18 primed human basophils for higher LT-synthesis. Thus, both IL-3 and IL-18 might be important factors for regulating LT-synthesis during the differentiation of human basophils.

TLR9- and FcεRI-Mediated Responses Oppose One Another in Plasmacytoid Dendritic Cells by Down-Regulating Receptor Expression

Plasmacytoid dendritic cells (pDC) express not only TLR9 molecules through which ligation with CpG DNA favors Th1 responses but also possess IgE receptors (FcepsilonRI) implicated in allergen presentation and induction of Th2 responses. This dichotomy prompted an investigation to determine whether TLR9- and IgE receptor-mediated responses oppose one another in pDC by affecting receptor expression and associated functional responses. Results showed that IgE cross-linking reduced TLR9 in pDC and inhibited the capacity of these cells to secrete IFN-alpha when stimulated with the CpG oligodeoxynucleotide (ODN)-2216. In contrast, an approximately 15-fold reduction in FcepsilonRIalpha mRNA and a loss in surface protein were seen in pDC first exposed to TLR9 ligation with ODN-2216. Results indicated that type I IFNs partly mediated this effect, as rIFN-alpha also caused a significant approximately 4-fold reduction in FcepsilonRIalpha mRNA. Finally, this reduction in FcepsilonRIalpha mediated by ODN-2216 correlated with a selective suppression of allergen-induced CD4+ T cell proliferation, but not of responses resulting from tetanus toxoid. Overall, these results imply mechanisms by which specific innate and IgE-dependent immune responses counterregulate one another at the dendritic cell level and may have significant impact on whether an ensuing response is either of Th1 or Th2 in nature.

Neurotrophin effects on eosinophils in allergic inflammation

Elevated neurotrophin concentrations have been shown in nasal and bronchoalveolar lavage fluids as well as in the sera of patients with allergic rhinitis and asthma. Concentration of nerve growth factor correlated with disease severity, bronchial hyperreactivity, and levels of mediators released from eosinophils. Due to the release of cationic proteins, oxygen species, and cytokines after degranulation, eosinophils contribute to tissue damage and can influence airway hyperresponsiveness in asthma. It has been hypothesized that neurotrophins may be involved in the development of eosinophilia and in activation of these cells. The aim of this review is to elucidate the direct and indirect mechanisms of neurotrophins contributing to eosinophilia in allergic diseases.

Nerve growth factor influences IgE-mediated human basophil activation: functional properties and intracellular mechanisms compared with IL-3

NGF and IL-3 play a unique role in supporting human basophil differentiation and mediator secretion. Their importance in allergic disease is underlined further by studies showing elevated levels of these factors in asthmatics. Here, we compared the abilities of IL-3 and NGF to stimulate basophil histamine, IL-4 or IL-13 release, either directly or in conjunction with IgE-dependent stimulation and assessed the intracellular signals responsible. Our results show that the ability of IL-3 and NGF to enhance IgE-dependent histamine release are similar. Both factors also potentiated IgE-dependent IL-13 secretion to a greater degree than the release of histamine or IL-4. At high concentrations (100 ng/ml), IL-3 and NGF alone were capable of releasing cytokines but little histamine. These abilities of IL-3 and NGF to modulate basophil activation were sensitive to blockade by specific inhibitors of PI 3-kinase, p38 MAPK and PLC, but not PKC, suggesting that their effects are mediated considerably by pathways comparable to IgE-dependent signalling.

Nerve growth factor and its receptors in asthma and inflammation

Nerve growth factor (NGF) is a high molecular weight peptide that belongs to the neurotrophin family. It is synthesized by various structural and inflammatory cells and activates two types of receptors, the TrkA (tropomyosin-receptor kinase A) receptor and the p75(NTR) receptor, in the death receptor family. NGF was first studied for its essential role in neuronal growth and survival. Recent reports indicate that it may also help mediate inflammation, especially in the airways. Several studies in animals have reported that NGF may induce bronchial hyperresponsiveness, an important feature of asthma, by increasing sensory innervation. It may also induce migration and activation of inflammatory cells, which infiltrate the bronchial mucosa, and of structural cells, including epithelial, smooth muscle cells and pulmonary fibroblasts. Increased NGF expression and release is observed in asthma patients after bronchial provocation with allergen. Taken together, the data from the literature suggest that NGF may play a role in inflammation, bronchial hyperresponsiveness and airway remodelling in asthma and may help us to understand the neuro-immune cross-talk involved in chronic inflammatory airway diseases.

Toll-like receptor 2 ligands activate human basophils for both IgE-dependent and IgE-independent secretion

BACKGROUND

Toll-like receptor (TLR) molecules play a critical role in directing the course of acquired immunity, including that associated with allergic disease, by recognizing specific microbial products that activate immune cells for effector functions.

OBJECTIVE

We investigated whether human basophils express 2 such molecules (TLR2 and TLR4), and assessed whether putative ligands for these receptors activate nuclear factor kappaB (NFkappaB) and modulate mediator release and cytokine secretion either alone or in response to stimulation.

METHODS

Toll-like receptor expression was assessed by using RT-PCR and flow cytometry. Immunoblotting detected nuclear NFkappaB. Automated fluorometry, RIA, and ELISA detected concurrent changes in histamine, leukotriene C 4 , and cytokine, respectively, after culture with specific ligands.

RESULTS

mRNA and protein for TLR2 and TLR4 were detected in basophils. However, in assessing nuclear localization of NFkappaB as a measure of functional receptor responses, basophils selectively reacted only to peptidoglycan, a TLR2 ligand, and not to LPS, a TLR4 ligand. Likewise, basophils secreted both IL-4 and IL-13 in direct response to peptidoglycan but not to LPS. Although neither ligand induced histamine or leukotriene C 4 release, several TLR2-specific ligands augmented the secretion of these mediators (and cytokine) in response to IgE-dependent activation and of IL-13 in response to IgE-independent stimulation. Finally, a selective inhibitor of NFkappaB did not prevent these enhancing effects mediated by TLR2 ligands.

CONCLUSION

These data suggest that innate immune responses mediated through TLR2 play a role in augmenting allergic reactions, in part by modulating basophil cytokine secretion and mediator release independently of NFkappaB activation.

Role of human mast cells and basophils in bronchial asthma

Mast cells and basophils are the only cells expressing the tetrameric (alphabetagamma2) structure of the high affinity receptor for IgE (FcepsilonRI) and synthesizing histamine in humans. Human FcepsilonRI+ cells are conventionally considered primary effector cells of bronchial asthma. There is now compelling evidence that these cells differ immunologically, biochemically, and pharmacologically, which suggests that they might play distinct roles in the appearance and fluctuation of the asthma phenotype. Recent data have revealed the complexity of the involvement of human mast cells and basophils in asthma and have shed light on the control of recruitment and activation of these cells in different lung compartments. Preliminary evidence suggests that these cells might not always be detrimental in asthma but, under some circumstances, they might exert a protective effect by modulating certain aspects of innate and acquired immunity and allergic inflammation.

[Nerve growth factor (NGF) in inflammation and asthma]

INTRODUCTION

The nerve growth factor (NGF) is known as a factor involved in neuronal growth and survival. From recent studies it may also be considered as a mediator of inflammation, in particular in the airways.

STATE OF ART

Several animal studies have shown that NGF may increase the sensory innervation, and participate in the bronchial hyperresponsiveness and inflammation observed in the airways of asthmatic patients. Different cell types are capable of secreting NGF: inflammatory cells that infiltrate the bronchial mucosa, and structural cells such as epithelial cells, smooth muscle cells and pulmonary fibroblasts. Furthermore, increased NGF levels have been detected in the bronchoalveolar lavage fluid from asthmatic patients.

PERSPECTIVES AND CONCLUSION

Altogether, these results suggest that NGF may play a role in inflammation, bronchial hyperresponsiveness and airway remodelling in asthma, and may lead to a better understanding of the mechanisms occurring in chronic inflammatory diseases, in particular asthma.

Basophil CD63 expression assay on highly sensitized atopic donor leucocytes-a useful method in chronic autoimmune urticaria

BACKGROUND

The autoimmune subclass of chronic idiopathic urticaria (CU) has been characterized by the occurrence of biologically relevant IgG antibodies against the IgE molecule or the alpha chain of the high-affinity Fcepsilon receptor (FcepsilonRIalpha) on basophils and mast cells. These antibodies are usually detected by autologous serum skin testing and confirmed by histamine release studies, immunoblotting, or enzyme-linked immunosorbent assay, but not always.

OBJECTIVES

To detect autoantibodies to the FcepsilonRIalpha in sera of CU patients by a modified serum-induced basophil activation test measured by flow cytometry (FCM) and to evaluate the relationship between the in vitro functional test, the autologous serum skin test (ASST), and the serum levels of IgE, eosinophil cationic protein (ECP) and antithyroid antibodies.

METHODS

Sera of 30 patients with CU and 26 patients with systemic autoimmune diseases (systemic lupus erythematosus, dermatomyositis) were tested for CD63 activation marker expression on basophils by FCM. Leucocytes from two highly sensitized atopic donors (D(A1,) D(A2)) and one non-atopic donor (D(NA)) were incubated with patients' sera and double-labelled with anti-IgE and anti-CD63 antibodies. Subsequently, the percentage of CD63-expressing basophils was determined by using FCM. In all CU patients an ASST was carried out and the serum IgE, and ECP levels and antithyroid antibodies were evaluated.

RESULTS

Twelve patients had a positive ASST and 14 patients a positive CD63 expression assay. There was a strong correlation between the ASST and CD63 assay. Sera from patients with systemic autoimmune diseases did not raise positive CD63 expression on basophils. There was a moderate negative correlation between the occurrence of atopic serum markers (IgE, ECP) and the ability of sera to induce CD63 expression on basophil cells of D(A2) (P < 0.05). The female sex was preponderant and antithyroid antibodies were more frequent.

CONCLUSIONS

Our new technical observation demonstrates that basophils of highly sensitized atopic donors can be successfully used without priming with IL-3 for the in-vitro flow cytofluorimetric diagnosis of CU. With this investigation the characterization of the autoimmune origin of CU is based on an objective in vitro technique.

Assessment of determinants of optimum performance of the CAST-2000 ELISA procedure

The Cellular Antigen Stimulation Test (CAST), a recent innovation in the laboratory detection of allergen sensitivity, is a functional assay based on the release of sulphidoleukotrienes (LTs) from allergen-activated circulating basophils. The current study was undertaken to establish optimum determinants of this procedure. The results demonstrate that treatment of blood with preservative-free heparin in polypropylene containers, and removal of erythrocytes by selective lysis with 0.83% ammonium chloride are excellent alternatives to the use of CAST venepuncture tubes and dextran, respectively. Similarly, decreasing and increasing the leucocyte concentration by 0.5- and 4-fold, respectively, as well as omission of interleukin-3 (IL-3) were also without significant effect. However, treatment of leucocyte suspensions with bacterial endotoxin (>1 microg/ml) activated the release of sulphidoleukotrienes from basophils and/or other types of leucocytes. The findings of this study are clearly relevant, both with respect to cost and performance, when implementing the CAST in clinical immunology laboratories.

Interactions between the cells of the immune and nervous system: neurotrophins as neuroprotection mediators in CNS injury

Inflammatory processes in the central nervous system (CNS) are considered neurotoxic, although recent studies suggest that they also can be beneficial and confer neuroprotection (neuroprotective autoimmunity). Cells from the immune system have been detected in CNS injury and found to produce and secrete a variety of neurotrophins such as NGF, BDNF, NT-3 and NT-4/5, and to express (similarly to neuronal cells), members of the tyrosine kinase (Trk) receptor family such as TrkA, TrkB and TrkC. Indeed, autocrine and paracrine interactions are observed at the site of CNS injury, resulting in a variety of homologic-heterologic modulations of immune and neuronal cell function. The end result of the inflammatory process, neurotoxicity and/or neuroprotection, is a function of the fine balance between the two cellular systems, i.e., of the complex signaling relationships between anti-inflammatory neuroprotective factors (neurotrophins and other chemical mediators) and proinflammatory neurotoxic factors (TNF, free radicals, certain cytokines, etc.). Autoimmune neuroprotection is a novel therapeutic approach aimed at shifting the balance between the immune and neuronal cells towards survival pathways in a variety of CNS injuries. This review focuses on data supporting this concept and its future therapeutical implications for optic nerve injury and multiple sclerosis.

Neurotrophins and neurotrophin receptors in allergic asthma

The neurotrophins nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3 (NT-3) and NT-4 play a pivotal role in the development of the nervous system. Despite their well-known effects on neurons, elevated neurotrophin concentrations have been observed under pathological conditions in sera of patients with inflammatory disorders. Patients with asthma feature both airway inflammation and an abnormal airway reactivity to many unspecific stimuli, referred to as airway hyperresponsiveness, which is, at least partly, neuronally controlled. Interestingly, these patients show increased levels of neurotrophins in the blood as well as locally in the lung. It has been demonstrated that neurotrophin release from immune cells is triggered by allergen contact. The presence of neurotrophins and the neurotrophin receptors p75 (p75NTR), tyrosine kinase A (TrkA), TrkB and TrkC have been described in several immune cells. There is strong evidence for an involvement of neurotrophins in regulation of hematopoiesis and, in addition, in modulation of immune cell function in mature cells circulating in blood or resting in lymphatic organs and peripheral tissues. The aim of this review is to demonstrate possible roles of neurotrophins during an allergic reaction in consideration of the temporospatial compartimentalization.

IFN-alpha inhibits IL-3 priming of human basophil cytokine secretion but not leukotriene C4 and histamine release

BACKGROUND

Innate immune responses play a critical role in determining the course of acquired immunity, including that associated with allergic disease. Type I interferons, which are generated early in these reactions, are important soluble factors that prime for TH1-like activity.

OBJECTIVE

Because human basophils secrete IL-4 and IL-13 in response to both IgE-dependent and IgE-independent stimuli, we tested whether IFN-alpha, a major type I IFN, affects the production of these TH2 cytokines and/or mediator release from these cells.

METHODS

Basophils isolated from blood were treated with IFN-alpha in the presence and absence of IL-3 priming before stimulating through the IgE receptor to release histamine, leukotriene C4, and IL-4. Effects of IFN-alpha on IL-3-mediated IL-13 secretion and basophil survival were also tested. IFN-alpha receptor expression was determined by RT-PCR.

RESULTS

IFN-alpha specifically inhibited the effects IL-3 has on basophil cytokine secretion. Enhanced secretion of IL-4 resulting from IL-3 priming was significantly inhibited in cells concurrently cultured with IFN-alpha. This effect was specific for cytokine generation, because histamine and leukotriene C4 were unaffected. Furthermore, IFN-alpha blocked IL-13 secretion directly induced by IL-3. Although IFN-beta also possessed some inhibitory activity, IFN-gamma (a type II IFN) had no effect on basophil cytokine secretion. Basophils constitutively expressed mRNA for the type I IFN receptor, and IFN-alpha did not affect basophil viability with regard to inhibition of cytokine secretion.

CONCLUSIONS

These results support the belief that early innate immune responses resulting in IFN-alpha production negatively regulate allergic responses by also inhibiting priming of basophil cytokine release.

Neurotrophins and the immune system

The neurotrophins are a family of polypeptide growth factors that are essential for the development and maintenance of the vertebrate nervous system. In recent years, data have emerged indicating that neurotrophins could have a broader role than their name might suggest. In particular, the putative role of NGF and its receptor TrkA in immune system homeostasis has become a much studied topic, whereas information on the other neurotrophins is scarce in this regard. This paper reviews what is known about the expression and possible functions of neurotrophins and their receptors in different immune tissues and cells, as well as recent data obtained from studies of transgenic mice in our laboratory. Results from studies to date support the idea that neurotrophins may regulate some immune functions. They also play an important role in the development of the thymus and in the survival of thymocytes.