Vasoactive intestinal peptide induces S(alpha)/S(mu) switch circular DNA in human B cells

The G Protein-Coupled Receptor, VPAC1, Mediates Vasoactive Intestinal Peptide-Dependent Functional Homeostasis of the Gut Microbiota

BACKGROUND AND AIMS

Vasoactive intestinal peptide (VIP) is a neuropeptide involved in the regulation of feeding behavior and circadian rhythms, metabolism, and immunity. Previous studies revealed the homeostatic effects of VIP signaling on the gut microbiota. VIP-deficient mice demonstrate a gut microbiota dysbiosis characterized by reduced α-diversity and decreased relative abundance (RA) of Gram-positive Firmicutes. However, the mechanism by which VIP signaling affects changes in the microbiota is unknown.

METHODS

To investigate the role of the 2 cognate G protein-coupled receptors for VIP (VPAC1 and VPAC2) in VIP-mediated homeostasis of the microbiota, fecal samples from VPAC1- and VPAC2-deficient, heterozygous, and wild-type littermate mice were assessed via targeted amplicon sequencing. Their microbiota profiles were additionally compared with microbiota from VIP-deficient, heterozygous, and wild-type littermates, where genotype-dependent changes in the composition and predicted function of each cohort were compared.

RESULTS

While wild-type mice in each line differed in α-diversity and β-diversity, consistent changes in both metrics were observed in VIP-deficient and VPAC1-deficient mice. This includes a dramatic reduction in α-diversity, increased RA of Proteobacteria and Bacteroidetes, and decreased RA of Lachnospiraceae, Ruminococcaceae, Muribaculaceae, and Rikenellaceae. Specific amplicon sequence variants and predicted functions found to differ significantly based on VIP or VPAC1 genotype were concordant in their directions of change. Multiplatform predicted functional profiling suggested a defective VIP-VPAC1 axis was associated with reduced amino acid degradation along with reduced quinol and quinone biosynthesis. Furthermore, alterations in predicted functions include increased sugar degradation, nitrate reduction, and fatty acid biosynthetic pathways, among other changes.

CONCLUSION

We conclude that VIP signaling through VPAC1 is critical for the maintenance of normal function of the gut microbiota.

Neuroimmune communication in infection and pain: Friends or foes?

Clinically, a variety of micro-organisms cause painful infections. Before seen as bystanders in the context of infections, recent studies have demonstrated that, as immune cells, nociceptors can sense pathogen-derived products. Nociceptors and immune cells, therefore, have evolved to communicate with each other to control inflammatory and host responses against pathogens in a complementary way. This interaction is named as neuroimmune communication (or axon-axon immune reflex) and initiates after the release of neuropeptides, such as CGRP and VIP by neurons. By this neurogenic response, nociceptors orchestrate the activity of innate and adaptive immune cells in a context-dependent manner. In this review, we focus on how nociceptors sense pathogen-derived products to shape the host response. We also highlight the new concept involving the resolution of inflammation, which is related to an active and time-dependent biosynthetic shift from pro-inflammatory to pro-resolution mediators, the so-called specialized pro-resolving lipid mediators (SPMs). At very low doses, SPMs act on specific receptors to silence nociceptors, limit pain and neurogenic responses, and resolve infections. Furthermore, stimulation of the vagus nerve induces SPMs production to regulate immune responses in infections. Therefore, harnessing the current understanding of neuro-immune communication and neurogenic responses might provide the bases for reprogramming host responses against infections through well balanced and effective immune response and inflammation resolution.

T cell help to B cells: Cognate and atypical interactions in peripheral and intestinal lymphoid tissues

Enduring immunity against harmful pathogens depends on the generation of immunological memory. Serum immunoglobulins are constantly secreted by long-lived antibody-producing cells, which provide extended protection from recurrent exposures. These cells originate mainly from germinal center structures, wherein B cells introduce mutations to their immunoglobulin genes followed by affinity-based selection. Generation of high-affinity antibodies relies on physical contacts between T and B cells, a process that facilitates the delivery of fate decision signals. T-B cellular engagements are mediated through interactions between the T cell receptor and its cognate peptide presented on B cell major histocompatibility class II molecules. Here, we describe the cellular and molecular aspects of these cognate T-B interactions, and highlight exceptional cases, especially those arising at intestinal lymphoid organs, at which T cells provide help to B cells in an atypical manner, independent of T cell specificity.

Defective formation of IgA memory B cells, Th1 and Th17 cells in symptomatic patients with selective IgA deficiency

Objective

Selective IgA deficiency (sIgAD) is the most common primary immunodeficiency in Western countries. Patients can suffer from recurrent infections and autoimmune diseases because of a largely unknown aetiology. To increase insights into the pathophysiology of the disease, we studied memory B and T cells and cytokine concentrations in peripheral blood.

Methods

We analysed 30 sIgAD patients (12 children, 18 adults) through detailed phenotyping of peripheral B‐cell, CD8⁺ T‐cell and CD4⁺ T‐cell subsets, sequence analysis of IGA and IGG transcripts, in vitro B‐cell activation and blood cytokine measurements.

Results

All patients had significantly decreased numbers of T‐cell‐dependent (TD; CD27⁺) and T‐cell‐independent (TI; CD27⁻) IgA memory B cells and increased CD21^low B‐cell numbers. IgM⁺IgD⁻ memory B cells were decreased in children and normal in adult patients. IGA and IGG transcripts contained normal SHM levels. In sIgAD children, IGA transcripts more frequently used IGA2 than controls (58.5% vs. 25.1%), but not in adult patients. B‐cell activation after in vitro stimulation was normal. However, adult sIgAD patients exhibited increased blood levels of TGF‐β1, BAFF and APRIL, whereas they had decreased Th1 and Th17 cell numbers.

Conclusion

Impaired IgA memory formation in sIgAD patients is not due to a B‐cell activation defect. Instead, decreased Th1 and Th17 cell numbers and high blood levels of BAFF, APRIL and TGF‐β1 might reflect disturbed regulation of IgA responses in vivo.

These insights into B‐cell extrinsic immune defects suggest the need for a broader immunological focus on genomics and functional analyses to unravel the pathogenesis of sIgAD.

LRRK2: An Emerging New Molecule in the Enteric Neuronal System That Quantitatively Regulates Neuronal Peptides and IgA in the Gut

BACKGROUND

Leucine-rich repeat kinase 2 (LRRK2) is a recently discovered molecule associated with familial and sporadic Parkinson's disease. It regulates many central neuronal functions such as cell proliferation, apoptosis, autophagy, and axonal extension. However, in contrast to the well-documented function of LRRK2 in central neurons, it is unclear whether LRRK2 is expressed in enteric neurons and affects the physiology of the gut.

AIMS

By examining LRRK2-KO mice, this study investigated whether enteric neurons express LRRK2 and whether intestinal neuronal peptides and IgA are quantitatively changed.

METHODS

Intestinal protein lysates and sections prepared from male C57BL/6 J mice were analyzed by Western blotting and immunostaining using anti-LRRK2 antibody, respectively. Intestinal neuronal peptide-mRNAs were quantified by real-time PCR in wild-type mice and LRRK2-KO mice. Intestinal IgA was quantified by ELISA. Lamina propria mononuclear cells (LPMCs) were analyzed by flow cytometry to evaluate the ratio of B1 to B2 B cells.

RESULTS

Western analysis and immunostaining revealed that LRRK2 is expressed in enteric neurons. The amounts of mRNA for vasoactive intestinal peptide, neuropeptide Y, and substance P were increased in LRRK2-KO mice accompanied by an increment of IgA. However, the intestinal B cell subpopulations were not altered in LRRK2-KO mice.

CONCLUSIONS

For the first time, we have revealed that LRRK2 is expressed in enteric neurons and related to quantitative alterations of neuronal peptide and IgA. Our study highlights the importance of LRRK2 in enteric neurons as well as central neurons.

The Regulation of Immunological Processes by Peripheral Neurons in Homeostasis and Disease

The nervous system and the immune system are the principal sensory interfaces between the internal and external environment. They are responsible for recognizing, integrating, and responding to varied stimuli, and have the capacity to form memories of these encounters leading to learned or 'adaptive' future responses. We review current understanding of the cross-regulation between these systems. The autonomic and somatosensory nervous systems regulate both the development and deployment of immune cells, with broad functions that impact on hematopoiesis as well as on priming, migration, and cytokine production. In turn, specific immune cell subsets contribute to homeostatic neural circuits such as those controlling metabolism, hypertension, and the inflammatory reflex. We examine the contribution of the somatosensory system to autoimmune, autoinflammatory, allergic, and infectious processes in barrier tissues and, in this context, discuss opportunities for therapeutic manipulation of neuro-immune interactions.

Evidence of a novel allergenic protein Narcin in the bulbs of Narcissus tazetta

Several plant-derived allergens have been identified which result in the formation of immunoglobulin E antibodies. Primarily, these allergens belong to the protein families including seed storage proteins, structural proteins and pathogenesis-related proteins. Several allergens are also reported from flower bulbs which cause contact dermatitis. Such symptoms are highly common with the bulb growers handling different species of Narcissus. Narcissus toxicity is also reported if the bulbs are consumed accidentally. The present study aimed to characterize the protein from the bulbs of Narcissus tazetta responsible for its allergenic response. A 13 kDa novel allergenic protein, Narcin was isolated from the bulbs of Narcissus tazetta. The protein was extracted using ammonium sulfate fractionation. The protein was further purified by anion exchange chromatography followed by gel filtration chromatography. The N-terminal sequence of the first 15 amino-acid residues was determined using Edman degradation. The allergenicity of the protein was measured by cytokine production using flow cytometry in peripheral blood mononuclear cells. Further estimation of total IgE was performed by ELISA method. This novel protein was found to induce pro-inflammatory cytokines and thus induce allergy by elevating total IgE level. The novel protein, Narcin isolated from Narcissus tazetta was found to exhibit allergenic properties.

Induction of gut IgA production through T cell-dependent and T cell-independent pathways

The gut immune system protects against mucosal pathogens, maintains a mutualistic relationship with the microbiota, and establishes tolerance against food antigens. This requires a balance between immune effector responses and induction of tolerance. Disturbances of this strictly regulated balance can lead to infections or the development inflammatory diseases and allergies. Production of secretory IgA is a unique effector function at mucosal surfaces, and basal mechanisms regulating IgA production have been the focus of much recent research. These investigations have aimed at understanding how long-term IgA-mediated mucosal immunity can best be achieved by oral or sublingual vaccination, or at analyzing the relationship between IgA production, the composition of the gut microbiota, and protection from allergies and autoimmunity. This research has lead to a better understanding of the IgA system; but at the same time seemingly conflicting data have been generated. Here, we discuss how gut IgA production is controlled, with special focus on how differences between T cell-dependent and T cell-independent IgA production may explain some of these discrepancies.

The surgical management of allergic rhinitis

In their discussion of the treatment of allergic rhinitis, the authors present key features of the disease and its management, allergen responses, the role of the inferior turbinate, and reviews of outcomes with submucosal resection, total inferior turbinectomy, cryosurgery, laser cautery, radical turbinectomy, submucous turbinectomy, submucous electrocautery, and microdebriber turbinoplasty. The authors discuss radiofrequency ablation and coblation outcomes and complications, along with the role of endoscopic sinus surgery in allergic rhinitis and emphasize the need for Otolaryngologists to be facile with a variety of procedures for best outcomes.

The absence of VPAC2 leads to aberrant antibody production in Aspergillus fumigatus sensitized and challenged mice

Vasoactive intestinal peptide (VIP) facilitates a "pro-allergy" phenotype when signaling through its G protein-coupled receptor, VPAC(2). We have shown that VPAC(2) knock-out (KO) mice developed an allergic phenotype marked by eosinophilia and elevated serum IgE. Therefore, we hypothesized that the humoral response to allergen challenge in these mice was T(H)2 dominant similar to wild-type (WT) C57BL/6 mice. Antibody responses in WT and KO mice were measured after Aspergillus fumigatus conidia inhalation. In contrast to previous reports, basal levels of serum IgG(2a) and IgA were significantly higher in naïve VPAC(2) KO animals. Antibody availability in the serum as well as the bronchoalveolar lavage fluid after fungal challenge was dominated by the pro-inflammatory isotype IgG(2a) and the mucosal isotype, IgA. IgA localizing cells dominated in the peribronchovascular areas of allergic KO mice while IgE immune complexes were found in WT allergic lungs. This research shows for the first time that VPAC(2) has a significant effect on antibody regulation, in the context of allergy.

Regulation of IgA responses in cattle, humans and mice

Secretory IgA (SIgA) constitutes the largest component of the humoral immune system of the body with gram quantities of this isotype produced by mammals on a daily basis. Secretory IgA (SIgA) antibodies function by both blocking pathogen/commensal entry at mucosal surfaces and virus neutralization. Several pathways of induction of IgA responses have been described which depend on T cells (T cell dependent or TD) pathways or are independent of T cells (T-independent or TI) and are mediated by dendritic cells (DCs) and/or epithelial cells. Many elements of IgA regulation readily cross species barriers (adjuvants, soluble and cognate factors) and are highly conserved whereas other pathways may be more specific to any given species and must be evaluated. Regulation of IgA production in cattle is not completely understood and thus we have focused in part on highly conserved factors such as transforming growth factor beta, Type I and Type 2 interferons, neuropeptides which interdigitate mucosal tissues (vasoactive intestinal peptide or VIP), and a small peptide (IgA inducing peptide or IGIP) which can serve as targets for modulation and increasing SIgA virus-specific antibodies. We have evaluated the potential utility of modulating these factors in vitro in regulation of qualitative aspects of antibodies of the IgM, IgG and IgA isotypes at mucosal surfaces and in secretions of the upper and lower respiratory tract to a virus of economic and public health importance, foot and mouth disease virus (FMDV). IgA responses in cattle are essential for host defense in response to various infectious agents. In cattle, IgA is not released into the colostrum, as is the case for other mammals but only IgG1 is selectively transported. In previous studies in cattle, IgA has been shown to be regulated by several cytokines including IFN-gamma, Type I interferons such as IFN-alpha and IFN-tau, transforming growth factor beta, IgA inducing peptide and other potential factors such as APRIL and BlyS which have not yet been fully evaluated in cattle. Many of these factors, namely TGF-beta and Type I interferons block cell cycle progression which is an essential component of Ig class switching and thus these factors require additional regulatory factors such as IL-2 to drive cells through cell cycle resulting in class switch recombination. Among these factors, IgA inducing peptide was originally identified from a bovine gut associated lymphoid tissue expression library and is highly conserved in pigs and humans at >90% at the amino acid level. The factor is regulated differently in various species but is consistently produced by dendritic cells.

Innate signaling networks in mucosal IgA class switching

The past 20 years have seen a growing interest over the control of adaptive immune responses by the innate immune system. In particular, considerable attention has been paid to the mechanisms by which antigen-primed dendritic cells orchestrate the differentiation of T cells. Additional studies have elucidated the pathways followed by T cells to initiate immunoglobulin responses in B cells. In this review, we discuss recent advances on the mechanisms by which intestinal bacteria, epithelial cells, dendritic cells, and macrophages cross talk with intestinal T cells and B cells to induce frontline immunoglobulin A class switching and production.

A transcriptionally permissive epigenetic landscape at the vasoactive intestinal peptide receptor-1 promoter suggests a euchromatin nuclear position in murine CD4 T cells

T cells express receptors for neuropeptides that mediate immunological activities. Vasoactive intestinal peptide receptor-1 (VPAC1), the prototypical group II G protein coupled receptor, binds two neuropeptides with high-affinity, called vasoactive intestinal peptide and pituitary adenylate cyclase activating polypeptide. During T cell signaling, VPAC1 mRNA expression levels are significantly downregulated through a Src kinase dependent mechanism, thus altering the sensitivity for these neuropeptides during an immune reaction. Presently, it is unknown whether the mechanism that regulates VPAC1 during T cell signaling involves epigenetic changes. Therefore, we hypothesized that the epigenetic landscape consisting of diacetylation at H3K9/14 and trimethylation at H3K4, two transcriptionally permissive histone modifications, would parallel VPAC1 expression showing high enrichment in untreated T cells, but lower enrichment in alpha-CD3 treated T cells. To this end, quantitative chromatin immunoprecipitation (ChIP) analysis of H3K9/14ac and H3K4me3 was conducted using purified CD4(+) T cells, with CD45R(+) B cells as a negative control. Our data revealed that these histone modifications at the VPAC1 promoter did indeed parallel its mRNA levels between T and B lymphocytes, but did not decrease during T cell signaling. Collectively, these data strongly imply a euchromatin nuclear position for the VPAC1 locus irrespective of the activation status of T cells.

Human IgA-inducing protein from dendritic cells induces IgA production by naive IgD+ B cells

Over the last several years, there has been a great deal of progress in characterizing the role of dendritic cells (DCs) in the activation and modulation of B cells. DC-secreted chemokines can induce B cell trafficking to the lymph nodes. DC-produced survival factors such as B cell-activating factor of the TNF family and a proliferation-inducing ligand have been shown to be essential for B cell maturation, but have also been implicated in class-switch recombination and B cell lymphoma survival. Recently added to this list of DC-derived factors effecting B cells is IgA-inducing protein (IGIP). In this study, we characterize production of IGIP by human DCs, and examine its capacity to induce IgA class switching and differentiation of naive B cells in vitro. Monocyte-derived DCs were cultured in vitro with TLR agonists (TLR3, 4, 5, and 9) and other factors, including CD40 ligand, GM-CSF, and IL-4 as well as the neuropeptide vasoactive intestinal peptide. Under in vitro stimulation with vasoactive intestinal peptide and CD40L, IGIP mRNA expression could be up-regulated as much as 35-fold above nonstimulated samples within 12-48 h. Naive B cells cultured with exogenous recombinant human IGIP produced IgA in greater quantities than nonstimulated controls. Finally, we demonstrate that IGIP stimulation drives the production of mu-alpha switch circles from IgM(+)IgD(+) naive human B cells, indicating its role as an IgA switch factor.

Generation of Immunoglobulin diversity in human gut-associated lymphoid tissue

The organised gut associated lymphoid tissue (GALT) exists adjacent to an extensive and diverse luminal flora. The follicle associated epithelium and associated dendritic cells and lymphocytes form a tightly fortified gateway between the flora and the host that permits connectivity between them and chronic activation of the lymphoid compartment. As a consequence, plasma cell precursors are generated continuously, and in abundance, in GALT by clonal proliferation. Clonal proliferation alone on this scale would reduce the spectrum of B cell specificity. To compensate, GALT also houses molecular machinery that diversifies the receptor repertoire by somatic hypermutation, class switch recombination and receptor revision. These three processes of enhancing the diversity of mature B cells ensure that although clonally related plasma cells may secrete immunoglobulin side by side in the mucosa they rarely have identical antigen binding sites.

Role of retinoic acid in the imprinting of gut-homing IgA-secreting cells

Antibody-secreting cells (ASCs) lodging in the mucosa of the small intestine are derived from activated B cells that are thought to arise in gut-associated lymphoid tissues (GALT). Upon leaving the GALT, B cells return to the blood where they must express the gut-homing receptors alpha4beta7 and CCR9 in order to emigrate into the small bowel. Recent evidence indicates that gut-associated dendritic cells (DCs) in GALT induce gut-homing receptors on B cells via a mechanism that depends on the vitamin A metabolite retinoic acid (RA). In addition, although ASC associated with other mucosal tissues secrete IgA in an RA-independent fashion, the presence of high levels of RA in intestine and GALT can promote B cell class switching to IgA and thus, boost the production of IgA in the intestinal mucosa. Here, we discuss the role of RA in the imprinting of gut-homing ASC and the evidence linking RA with the generation of intestinal IgA-ASCs.

The regulation of IgA class switching

IgA class switching is the process whereby B cells acquire the expression of IgA, the most abundant antibody isotype in mucosal secretions. IgA class switching occurs via both T-cell-dependent and T-cell-independent pathways, and the antibody targets both pathogenic and commensal microorganisms. This Review describes recent advances indicating that innate immune recognition of microbial signatures at the epithelial-cell barrier is central to the selective induction of mucosal IgA class switching. In addition, the mechanisms of IgA class switching at follicular and extrafollicular sites within the mucosal environment are summarized. A better understanding of these mechanisms may help in the development of more effective mucosal vaccines.

Differentiation and homing of IgA-secreting cells

Most antibody-secreting cells (ASCs) in mucosal tissues produce immunoglobulin A (IgA), the most abundant immunoglobulin in the body and the main class of antibody found in secretions. IgA-ASCs differentiate in the mucosal-associated lymphoid tissues and are usually considered as a homogeneous population of cells. However, IgA-ASCs that travel to the small intestine have unique characteristics in terms of their migratory requirements. These IgA-ASCs require the homing molecules alpha4beta7 and CCR9 to interact with their ligands, mucosal addressin cell adhesion molecule-1 and CCL25, which are constitutively expressed in the small intestine. Indeed, recent work has shown that IgA-ASCs specific for the small bowel are generated under different conditions as compared with IgA-ASCs in other mucosal compartments. Moreover, the mechanisms inducing IgA class switching may also vary according to the tissue where IgA-ASCs differentiate. Here we describe the mechanisms involved in the differentiation of IgA-ASCs in mucosal compartments, in particular those involved in the generation of gut-homing IgA-ASCs.

The significance of vasoactive intestinal peptide in immunomodulation

First identified by Said and Mutt some 30 years ago, the vasoactive intestinal peptide (VIP) was originally isolated as a vasodilator peptide. Subsequently, its biochemistry was elucidated, and within the 1st decade, their signature features as a neuropeptide became consolidated. It did not take long for these insights to permeate the field of immunology, out of which surprising new attributes for VIP were found in the last years. VIP is rapidly transforming into something more than a mere hormone. In evolving scientifically from a hormone to a novel agent for modifying immune function and possibly a cytokine-like molecule, VIP research has engaged many physiologists, molecular biologists, biochemists, endocrinologists, and pharmacologists and it is a paradigm to explore mutual interactions between neural and neuroendocrine links in health and disease. The aim of this review is firstly to update our knowledge of the cellular and molecular events relevant to VIP function on the immune system and secondly to gather together recent data that support its role as a type 2 cytokine. Recognition of the central functions VIP plays in cellular processes is focusing our attention on this "very important peptide" as exciting new candidates for therapeutic intervention and drug development.

Interactions between the enteric nervous system and the immune system: role of neuropeptides and nutrition

Neuropeptidergic synthesis occurs in enteric nerves and immune cells of the gut-associated lymphoid tissue. Lymphocytes, macrophages, mast cells, and intestinal epithelial cells are capable of responding to these neuropeptides. Neuropeptides generate proliferative or antiproliferative responses of mucosal lymphocytes and intestinal epithelial cells, affect cytokine production and immunoglobulin synthesis by immune cells, and control secretion of water and electrolytes. Some neuropeptides, particularly cholecystokinin, gastrin-releasing peptide, and neurotensin, appear promising to maintain mucosal immunity in patients who cannot receive enteral feeding during critical illness or after GI tract loss. Exogenous administration of neuropeptides to preserve normal immune defenses represents a potential new field of pharmacotherapeutics against bacterial invasion.

Accessibility control and machinery of immunoglobulin class switch recombination

Immunoglobulin (Ig) class switching is a process by which B lymphocytes shift from production of IgM to other Ig classes and subclasses via Ig class switch recombination (CSR). Multiple cellular and molecular processes are involved in CSR. Induction of a given IgH germline transcription initiates CSR processes. Ig germline transcription is selectively activated and induced by specific cytokine(s) via cytokine-specific signal pathways, synergized by CD40 signaling, and optimized by the 3' Ig alpha enhancers through locus control region function. Following Ig germline transcription, the switch-region DNA undergoes conformational changes so that it can serve as an appropriate substrate for nicking and cleavage by switch recombination machinery. Finally, the double-strand breaks in donor and acceptor switch DNAs are processed, repaired, and ligated through a general nonhomologous end join pathway. CSR generates a new transcriptional unit for production of a class-switched Ig isotype.

Immunoeffector and immunoregulatory activities of vasoactive intestinal peptide

Vasoactive intestinal peptide (VIP) and its two G protein-coupled receptors, VPAC1R and VPAC2R, are prominent in the immune system and potently affect T cells and macrophages. VPAC1Rs are expressed constitutively by blood and tissue T cells, with an order of prevalence of Th2>Th1>>Ts, and transmit signals suppressive for migration, proliferation and cytokine production. Immune activation of T cells downregulates VPAC1Rs and upregulates VPAC2Rs. VPAC2Rs mediate T cell chemotaxis, stimulation of some Th2-type cytokines, and inhibition of some Th1-type cytokines. A tentative hypothesis that the VIP-VPAC2R axis is the major neuroregulator of Th2/Th1 balance has been confirmed by finding an increased ratio in CD4 T cells of transgenic (TG) mice, expressing high levels of VPAC2Rs, and a decreased ratio in CD4 T cells of VPAC2R-null (K/O) mice. VPAC2R TG mice exhibit an allergic phenotype, whereas the K/O mice are hypoallergic and have heightened delayed-type hypersensitivity. The mechanisms of VIP-VPAC2R effects include decreased Th2 apoptosis, increased Th2-type cytokine production, and greater generation of Th2 memory cells. VPAC2R antagonists are being developed to alleviate allergic diseases and strengthen effector Th1 cell-mediated immunoprotection.

Expression and fine mapping of murine vasoactive intestinal peptide receptor 1

Vasoactive intestinal peptide (VIP) plays multiple roles in the nervous, endocrine, and immune systems as a neurotransmitter, a hormone, and a cytokine. VIP is widely distributed in neurons of the central and peripheral nervous systems (CNS/PNS), and recently has been found to be an important neuroprotective agent. VIP actions are mediated through specific G protein-coupled receptors. We have cloned the cDNA of VIP receptor subtype 1 (VIPR1 or VPAC1) and have demonstrated the quantitative expression profile in mice. Fluorometric real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis demonstrated that VPAC1 is expressed in all tissues examined. Expression was highest in the small intestine and colon followed by the liver and brain. The high level of VPAC1 expression in forebrain and cerebellum suggests that VPAC1 may mediate the neuroprotective effect of VIP. We have refined the chromosomal localization of the mouse, rat, and human VPAC1 genes. This fine mapping of the VPAC1 gene extends the respective regions of synteny between the distal region of mouse chromosome 9, rat chromosome 8q32, and human chromosome 3p21.33-p21.31. Thus, VPAC, constitutes a functional-positional candidate for the tumor-suppressor function mapped to human 3p22-p21 where loss-of-heterozygosity is observed in small-cell lung carcinoma (SCLC) cell lines and primary tumors. Availability of the cDNA sequences for mouse VPAC1 will facilitate the generation of VPAC1 null mutant animals. Such studies will ultimately enhance our understanding of the role of VIP in the nervous system.

Expression and fine mapping of murine vasoactive intestinal peptide receptor 1

Vasoactive intestinal peptide (VIP) plays multiple roles in the nervous, endocrine, and immune systems as a neurotransmitter, a hormone, and a cytokine. VIP is widely distributed in neurons of the central and peripheral nervous systems (CNS/PNS), and recently has been found to be an important neuroprotective agent. VIP actions are mediated through specific G protein-coupled receptors. We have cloned the cDNA of VIP receptor subtype 1 (VIPR1 or VPAC1) and have demonstrated the quantitative expression profile in mice. Fluorometric real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis demonstrated that VPAC1 is expressed in all tissues examined. Expression was highest in the small intestine and colon followed by the liver and brain. The high level of VPAC1 expression in forebrain and cerebellum suggests that VPAC1 may mediate the neuroprotective effect of VIP. We have refined the chromosomal localization of the mouse, rat, and human VPAC1 genes. This fine mapping of the VPAC1 gene extends the respective regions of synteny between the distal region of mouse chromosome 9, rat chromosome 8q32, and human chromosome 3p21.33-p21.31. Thus, VPAC, constitutes a functional-positional candidate for the tumor-suppressor function mapped to human 3p22-p21 where loss-of-heterozygosity is observed in small-cell lung carcinoma (SCLC) cell lines and primary tumors. Availability of the cDNA sequences for mouse VPAC1 will facilitate the generation of VPAC1 null mutant animals. Such studies will ultimately enhance our understanding of the role of VIP in the nervous system.

Allergic diathesis in transgenic mice with constitutive T cell expression of inducible vasoactive intestinal peptide receptor

Vasoactive intestinal peptide (VIP) and its G-protein-coupled receptors (VPAC1 and VPAC2 Rs) are prominent in the immune system. In T cells, VPAC1 R is expressed constitutively whereas VPAC2 R is induced only after stimulation of the T cell receptor (TCR) or exposure to some cytokines. VPAC1 R and VPAC2 R also transduce different effects of VIP on T cells. Constitutive expression of VPAC2 R selectively in CD4+ T cells (helper-inducer Th cells) of transgenic (TG) C57BL/6 mice directed by the lck tyrosine kinase promoter is now shown to evoke production of more Th2-type interleukins 4 and 5, and less Th1-type interferon gamma after TCR activation. VPAC2 R TG mice consequently have significant elevations of blood IgE, IgG1, and eosinophils. VPAC2 R TG mice also show increased IgE antibody responses, which mediate heightened cutaneous allergic reactions, and have depressed delayed-type hypersensitivity. VIP enhancement of the ratio of Th2 cell to Th1 cell cytokines thus evokes an allergic state in normally nonallergic mice, which suggests the possibility of neuropeptide contributions to immune phenotypic alterations in human hypersensitivity diseases.

Regulation of vasoactive intestinal peptide receptor expression in developing nervous systems

Vasoactive intestinal peptide (VIP) is a 28-amino acid peptide that has several functions, including the regulation of water and electrolyte secretion, hormone and cytokine release, bronchodilitation, and neurogenesis. VIP effects are mediated by specific G-protein coupled receptors. Three distinct receptor subtypes, with differing affinity for VIP, have been cloned and characterized as receptors 1 and 2 (VPAC1 and VPAC2) and pituitary adenylate cyclase activating polypeptide receptor (PAC1). Our laboratory has demonstrated that upregulation of VPAC1 in SK-N-SH neuroblastoma cells results in marked shift in cell type to the glial lineage with a corresponding loss of neuronal lineage and suppression of xenograft tumor growth. To understand the molecular mechanisms responsible for regulation of the VPAC1 gene in neuronal lineage, we have cloned and sequenced 2.6-kb of the 5'-flanking sequences of the human VPAC1 gene. Sequence analysis demonstrated that the human VPAC1 promoter sequence contains putative binding sites for several known transcription factors, including Sp1, NFkB, and cETS-1. To study the temporal and spatial expression pattern of human VPAC1 promoter sequences, we have generated transgenic mice expressing the bacterial beta-galactosidase gene under the control of the 2.6-kb 5'-flanking and promoter sequence of the human VPAC1 gene. Transgene expression was detected in brain, spinal cord, and lung in 14-day-old animals. Taken together, these results demonstrate that VPAC1 may play an important role in the nervous system, and suggest a role for VIP in neuronal differentiation.

Danger signals: SOS to the immune system

The activation of dendritic cells, necessary for the initiation of primary and secondary immune responses, can be induced by endogenous danger signals - released by tissues undergoing stress, damage or abnormal death - and also by exogenous danger signals elaborated by pathogens. Some endogenous danger signals that recently have been discovered are heat-shock proteins, nucleotides, reactive oxygen intermediates, extracellular-matrix breakdown products, neuromediators and cytokines like the IFNs. We propose that allergy may be initiated by the direct damage of dendritic or other cells by toxic chemicals and allergenic proteases, and suggest that the triggering of danger signal receptors by exogenous pathogen-derived molecules may be more to the advantage of the pathogen than to the host.

Production of interferon-gamma by tonsillar mononuclear cells in IgA nephropathy patients

Much evidence, both in vivo and in vitro, suggests that patients with IgA nephropathy (IgAN) have enhanced IgA production. We hypothesized that Haemophilus parainfluenzae (HP) in the tonsil plays an important role in the IgA production of IgAN patients. In this study, we focused on interferon-gamma (IFN-gamma) and IgA production by tonsillar mononuclear cells (TMC) in patients with IgAN. Tonsillectomies were performed in patients with IgAN and chronic tonsillitis (CT). The induction of IFN-gamma and IgA in vitro by TMC from IgAN patients was compared with that from CT patients. In addition, we investigated whether stimulation with the outer membranes of HP (OMHP) enhanced IFN-gamma and IgA induction by TMC from patients with IgAN. Spontaneous IFN-gamma production and spontaneous total IgA production by TMC were higher in IgAN patients than in those patients with CT (p < 0.05). IFN-gamma induction by OMHP stimulation was also higher in IgAN patients than in CT patients. The stimulation of OMHP enhanced HP-specific IgA in IgAN but had no influence on the production of IFN-gamma in patients with either IgAN or CT compared with spontaneous IFN-gamma production. IFN-gamma production was positively correlated with total IgA values in both IgAN and CT patients, but not with HP-specific IgA. These results suggest that increased IFN-gamma production in patients with IgAN is not associated with HP infection but may play a role in the pathogenesis of IgAN.

Induction of IgA against Haemophilus parainfluenzae antigens in tonsillar mononuclear cells from patients with IgA nephropathy

Much evidence suggests that IgA production in vivo and in vitro is enhanced in patients with IgA nephropathy (IgAN). We have demonstrated glomerular deposition of the outer membranes of Haemophilus parainfluenzae (HP) antigens (OMHP) and the presence of HP-specific IgA in the serum of patients with IgAN. In this study, we investigated the production of IgA and several cytokines by tonsillar mononuclear cells (TMC) from IgAN patients induced by stimulation with OMHP. The spontaneous production of total IgA and TGF-beta by TMC from IgAN patients was higher than that by TMC from patients with chronic tonsillitis (CT) (P < 0.05). Stimulation with OMHP in vitro enhanced the production of HP-specific IgA by TMC from IgAN patients (P < 0.01), but not by TMC from CT patients. OMHP stimulation also enhanced the production of TGF-beta and IL-10 by TMC from IgAN patients (P < 0.001). These results suggest that the infection of HP in the tonsil may be involved in the etiology of IgAN.

IL-4 regulates VIP receptor subtype 2 mRNA (VPAC2) expression in T cells in murine schistosomiasis

In murine schistosomiasis, granuloma T cells express VPAC2 mRNA, whereas there is none in splenocytes. This suggests that T cell VPAC2 mRNA is inducible. To address this issue, splenocytes from schistosome-infected mice were incubated with anti-CD3 to induce VPAC2 mRNA, which only appeared when cell cultures also contained anti-IL-4 mAb. Granuloma cells expressed VPAC2 mRNA. This natural expression decreased substantially when cells were cultured 3 days in vitro. However, granuloma cells cultured with anti-IL-4 mAb strongly expressed VPAC2 mRNA. IL-4 KO mice were examined to further address the importance of IL-4 in VPAC2 regulation. Splenocytes and dispersed granuloma cells from IL-4 KO animals had substantially more VPAC2 mRNA than those in wild-type controls. VPAC2 mRNA content decreased when cells were cultured with rIL-4. VPAC2 mRNA localized to CD4+ T cells. Th1 cell lines expressed VPAC2 mRNA much stronger than Th2 cells. Anti-IL-4 mAb increased VPAC2 mRNA expression in Th2 cells cultured in vitro. However, rIL-4 could not suppress VPAC2 mRNA expression in Th1 cells. Thus, VPAC2 is an inducible CD4+ T cell receptor, and IL-4 down-modulates VPAC2 mRNA expression in Th2 cells.

DNA from Mycobacterium bovis bacillus Calmette-Guérin (MY-1) inhibits immunoglobulin E production by human lymphocytes

A DNA fraction purified from Mycobacterium bovis bacillus Calmette-Guérin (BCG) and designated MY-1 induced interferon (IFN)-gamma production by human peripheral blood mononuclear cells (PBMC). IFN-gamma is well known as a downregulator of IgE production. In this study we investigated whether MY-1 regulates IgE production by human PBMC in vitro. MY-1 inhibited IgE production in PBMC taken from normal donors and stimulated with interleukin (IL)-4 plus monoclonal anti-CD40 antibody, without affecting production of IgA. MY-1 enhanced production of IFN-gamma and IL-12 by PBMC. Inhibition by MY-1 of IgE production was mediated by both IFN-gamma and IL-12, since the MY-1-induced suppression was blocked by the addition of monoclonal anti-IFN-gamma antibody, monoclonal anti-IL-12 antibody or a monoclonal antibody (mAb) directed at the IL-12 receptor. MY-1 inhibited the induction of epsilon germ-line transcript by IL-4. Additionally, MY-1 inhibited spontaneous in vitro production of IgE by PBMC from atopic donors in the absence of IL-4 plus anti-CD40 mAb. These results suggest that exposure to MY-1 may be a novel strategy for the treatment of IgE-related allergic disease.

Submucous turbinectomy decreases not only nasal stiffness but also sneezing and rhinorrhea in patients with perennial allergic rhinitis

BACKGROUND

Turbinate surgery, in which mucous epithelium is resected, has often been used for patients with perennial allergic rhinitis, since the mucous epithelium is the principal site for immunoglobulin (Ig)E-mediated allergic reactions and chronic inflammation.

OBJECTIVE

To assess the effect of submucous turbinectomy on allergic rhinitis.

METHODS

Sixty patients with severe perennial allergic rhinitis underwent submucous turbinectomy and were followed-up for 1 year. Nasal symptoms were evaluated with a standard symptom score. Rhinometry was used to evaluate nasal congestion, and nasal provocation tests in vivo were performed to evaluate allergic reactions. In 16 cases, biopsies from the nose were also available for immunohistochemical analysis. These examinations were performed before and after submucous turbinectomy.

RESULTS

The mean total nasal symptom score (7.2 +/- 1.7, mean +/- SD before surgery) was significantly reduced after surgery (1.2 +/- 1.4, P < 0.0001), and the effect of the surgery on nasal symptoms continued for at least 12 months (1.9 +/- 1.8, P < 0.0001). Submucous turbinectomy reduced both nasal discharge and sneezing, as well as nasal stiffness. Histopathological examination following surgery revealed that the lamina propria was occupied by fibrous tissues, and that the number of vessels, nasal glands, eosinophils and infiltrating IgE+ cells decreased in the turbinate. There were no significant differences in the levels of either house dust mite-specific or non-specific IgE in the serum between before and after surgery.

CONCLUSION

Submucous turbinectomy preserving the ciliary epithelium is a powerful strategy for improving nasal symptoms induced by allergic reaction via the reduction in the number of allergy-related cells in the nose.

Enhancement by vasoactive intestinal peptide of gamma-interferon production by antigen-stimulated type 1 helper T cells

Vasoactive intestinal peptide (VIP) is a neuroendocrine mediator in immune tissues that affects many T cell functions through two homologous high-affinity G-protein-coupled receptors, termed VIPR1 and VIPR2. Antigen-stimulated secretion of gamma-interferon (IFN-gamma) by sperm whale myoglobin-specific Th1 cells of DBA/2 mouse I-Ed-restricted clones, which express VIPR1 and VIPR2, was enhanced by 10(-10) M to 10(-7) M VIP. Enhancement of IFN-gamma secretion reached a mean maximum of fourfold for VIP and threefold for a VIPR2-selective agonist, without any effect of a VIPR1-selective agonist. Secretion of IFN-gamma by PMA and ionomycin-stimulated clones of Th1 cells was not altered by VIP. Antigen-stimulated secretion of IFN-gamma by T cell receptor-transgenic, influenza hemagglutinin-specific, and cytokine-differentiated mouse lymph node Th1 cells, which also express VIPR1 and VIPR2, was enhanced by 10(-10) M to 10(-8) M VIP. Enhancement of IFN-gamma secretion increased to a maximum of 14-fold for VIP, 14-fold for the VIPR2-selective agonist, and 20-fold for the VIPR1-selective agonist. In contrast to VIP suppression of interleukin production and lack of effect on IFN-gamma production by T cells stimulated with anti-CD3 antibody or a mitogenic lectin, generation of IFN-gamma by antigen-stimulated T cells is enhanced significantly by physiological concentrations of VIP.

CD40 engagement triggers switching to IgA1 and IgA2 in human B cells through induction of endogenous TGF-beta: evidence for TGF-beta but not IL-10-dependent direct S mu-->S alpha and sequential S mu-->S gamma, S gamma-->S alpha DNA recombination

IgA are major effectors of antimicrobial defense in the respiratory and digestive tracts. We have analyzed the requirements for and the modalities of switching to IgA using our recently identified monoclonal model of human germinal center differentiation, CL-01 B cells. CL-01 cells bear surface IgM (sIgM) and sIgD and switch to all seven downstream isotypes in response to physiologic stimuli. In these cells, CD40 engagement by CD40 ligand induces production of endogenous TGF-beta and IL-10, expression of germline Ialpha1-Calpha1 and Ialpha2-Calpha2 transcripts, mature VHDJH-Calpha1 and VHDJH-Calpha2 transcripts, and IgA secretion. These events are associated with not only direct Smu-->Salpha, but also sequential Smu-->Sgamma, Sgamma-->Salpha DNA recombination, and are ablated by neutralizing anti-TGF-beta but not IL-10 Ab, and indicating that TGF-beta, not IL-10, is a crucial mediator of the transcriptional activation and recombination of human Calpha1 and Calpha2 genes. Our findings in CL-01 cells were reproduced in freshly isolated naive sIgM+ sIgD+ B lymphocytes. Thus, engagement of CD40, in the absence of other (known) stimuli, is sufficient to effectively induce switching to IgA in human B cells. This is effected by direct and sequential DNA recombination events, which are both dependent upon endogenous TGF-beta secreted by the CD40L-induced B cells.

CD40 Engagement Triggers Switching to IgA1 and IgA2 in Human B Cells Through Induction of Endogenous TGF-β: Evidence for TGF-β But Not IL-10-Dependent Direct Sμ→Sα and Sequential Sμ→Sγ, Sγ→Sα DNA Recombination

IgA are major effectors of antimicrobial defense in the respiratory and digestive tracts. We have analyzed the requirements for and the modalities of switching to IgA using our recently identified monoclonal model of human germinal center differentiation, CL-01 B cells. CL-01 cells bear surface IgM (sIgM) and sIgD and switch to all seven downstream isotypes in response to physiologic stimuli. In these cells, CD40 engagement by CD40 ligand induces production of endogenous TGF-β and IL-10, expression of germline Iα1-Cα1 and Iα2-Cα2 transcripts, mature VHDJH-Cα1 and VHDJH-Cα2 transcripts, and IgA secretion. These events are associated with not only direct Sμ→Sα, but also sequential Sμ→Sγ, Sγ→Sα DNA recombination, and are ablated by neutralizing anti-TGF-β but not IL-10 Ab, and indicating that TGF-β, not IL-10, is a crucial mediator of the transcriptional activation and recombination of human Cα1 and Cα2 genes. Our findings in CL-01 cells were reproduced in freshly isolated naive sIgM+ sIgD+ B lymphocytes. Thus, engagement of CD40, in the absence of other (known) stimuli, is sufficient to effectively induce switching to IgA in human B cells. This is effected by direct and sequential DNA recombination events, which are both dependent upon endogenous TGF-β secreted by the CD40L-induced B cells.

Combined nasal challenge with diesel exhaust particles and allergen induces In vivo IgE isotype switching

In this study we undertook to provide evidence for local in vivo isotype switching to IgE following nasal challenges. Detection of deleted switch circular DNA (switch circles) by a novel nested polymerase chain reaction-based approach was employed as definitive molecular evidence of Ig isotype switching. Nasal challenge in humans with diesel exhaust particles (DEP) plus ragweed antigen has been shown to enhance local IgE production, stimulate local cytokine production, and markedly increase mucosal IgE antibody to ragweed. Four days after combined intranasal DEP plus ragweed challenge, we detected and characterized clones of deleted switch circular DNA (Sepsilon /Smu) representing switching from mu to epsilon from nasal lavage cells. No switch circular DNA was detected in nasal lavage cells following challenge with DEP alone nor with ragweed allergen alone. These results indicate that the combination of mucosal stimulation with DEP and ragweed allergen is capable of driving in vivo isotype switching to IgE in humans with ragweed allergy. These results are the first direct demonstration of in vivo IgE isotype switching in humans.

CD1-restricted T-cells influence IgG subclass and IgE production

BACKGROUND

Human CD1 has recently emerged as a third family of antigen-presenting molecules that is distinct from either major histocompatibility complex class I or class II.

OBJECTIVE

We investigated whether the CD1b-restricted T-cell interaction with antigen alters human IgG subclass and IgE isotype production.

METHODS

CD1b-restricted antigen-specific T cells derived from the skin lesion of a patient with leprosy were stimulated with their cognate antigen, lipoarabinomman (LAM) of Mycobacterium leprae, in the presence of CD1+ antigen-presenting cells and tested for their ability to alter IgG subclass and IgE production from IgD+ B cells.

RESULTS

CD1-restricted T cells cultured with CD1+ antigen-presenting cells in the absence of LAM induced IgG1, IgG3, IgG4, and IgE, whereas CD1b-restricted T cells cultured in the presence of LAM induced IgG1 and IgG3 and inhibited production of IgG4 and IgE. Production of IgG4 and IgE was rescued in the CD1-restricted system by the addition of anti-interferon-gamma. IgG2 production was not induced under any circumstances.

CONCLUSION

In this study we demonstrated that a specific CD1b-restricted T-cell line can behave similarly to classically-restricted Th1-type T cells. CD1b-restricted T-cells of this type may regulate immune responses to microbial pathogens by simultaneously enhancing cell-mediated immunity and downregulating IgG4 and IgE responses.

CD40 Ligand and Appropriate Cytokines Induce Switching to IgG, IgA, and IgE and Coordinated Germinal Center and Plasmacytoid Phenotypic Differentiation in a Human Monoclonal IgM+IgD+ B Cell Line

B lymphocytes are induced to undergo Ig class switching and a complex phenotypic differentiation by the milieu of the germinal center. Partly as a result of the lack of a suitable in vitro B cell model, the relationship between these processes in the humans has never been formally established in vitro. We have identified a human monoclonal B cell line, CL-01, that expresses surface IgM and IgD and, upon induction with CD40 ligand, IL-4, and IL-10, switches to all seven downstream isotypes, showing typical DNA switch recombination preceded by germline transcription of targeted CH regions. In CL-01 cells, switch-inducing stimuli trigger concomitant changes in expression of surface IgD, CD23, CD38, and CD77 that parallel those reported in ex vivo isolated tonsillar centroblasts, centrocytes, and memory B cells. Eventually, in the presence of IL-6, CL-01 cells express CD56 and accumulate cytoplasmic IgG and IgA, both traits of plasmacytoid differentiation. Analysis of transcription and recombination of the Ig H locus in sorted CL-01 cells suggest that Ig class switching begins in centroblasts, it extends to all isotypes in centrocytes, and it is extinct in memory B cells. Thus, we have induced coordinated Ig class switching, progression through germinal center phenotypic stages, and differentiation to memory B cells and plasma cells at the level of a single B clonotype. Our data suggest that these processes are likely regulated by a common maturation program, the activation of which may require CD40 ligand, IL-4, IL-10, and IL-6 only.

CD40 ligand and appropriate cytokines induce switching to IgG, IgA, and IgE and coordinated germinal center and plasmacytoid phenotypic differentiation in a human monoclonal IgM+IgD+ B cell line

B lymphocytes are induced to undergo Ig class switching and a complex phenotypic differentiation by the milieu of the germinal center. Partly as a result of the lack of a suitable in vitro B cell model, the relationship between these processes in the humans has never been formally established in vitro. We have identified a human monoclonal B cell line, CL-01, that expresses surface IgM and IgD and, upon induction with CD40 ligand, IL-4, and IL-10, switches to all seven downstream isotypes, showing typical DNA switch recombination preceded by germline transcription of targeted CH regions. In CL-01 cells, switch-inducing stimuli trigger concomitant changes in expression of surface IgD, CD23, CD38, and CD77 that parallel those reported in ex vivo isolated tonsillar centroblasts, centrocytes, and memory B cells. Eventually, in the presence of IL-6, CL-01 cells express CD56 and accumulate cytoplasmic IgG and IgA, both traits of plasmacytoid differentiation. Analysis of transcription and recombination of the Ig H locus in sorted CL-01 cells suggest that Ig class switching begins in centroblasts, it extends to all isotypes in centrocytes, and it is extinct in memory B cells. Thus, we have induced coordinated Ig class switching, progression through germinal center phenotypic stages, and differentiation to memory B cells and plasma cells at the level of a single B clonotype. Our data suggest that these processes are likely regulated by a common maturation program, the activation of which may require CD40 ligand, IL-4, IL-10, and IL-6 only.

Vasoactive intestinal peptide enhancement of antigen-induced differentiation of a cultured line of mouse thymocytes

The prominence of vasoactive intestinal peptide (VIP) in rodent thymic neurons suggested that this potent mediator of T cell functions may alter developmental responses of thymocytes to T cell receptor (TCR) -dependent stimulation. CD4+8+ DPK cells derived from a thymic lymphoma of a TCR transgenic mouse respond to pigeon cytochrome C (PCC) antigen in association with distinct I-E MHC II haplotypes on antigen-presenting cells (APCs) by differentiating into CD4+8- T cells. The specific recognition of VIP by two types of homologous G-protein-coupled receptors (VIPR1 and VIPR2) on DPK cells was attributable predominantly to VIPR1 before and to VIPR2 after exposure to APCs and PCC, as assessed by quantification of the respective mRNAs. PCC-evoked differentiation of DPK cells was enhanced significantly by 1 to 100 nM VIP after 3 to 4 days. The effects of VIP analogs with VIPR type selectivity implied that VIP enhancement of differentiation of DPK cells was mediated principally by VIPR2. Differential reduction in the expression of each type of VIPR by transfection of DPK cells with plasmids encoding the respective antisense mRNAs confirmed the central role of VIPR2 in VIP-enhanced conversion to CD4+8- T cells. The suppression of DPK cell differentiation by inhibitors of adenylyl cyclase and protein kinase A suggested a transductional role for VIP-elicited increases in [cAMP]i. That the changes in frequency of CD4+8+ and CD4+8- DPK cells reflected principally differentiation was supported by the lack of consistent differences between the two subsets in the effects of VIP and VIPR2 agonist on cell number, viability, apoptosis, and proliferation. VIP may be one endogenous mediator that explains the unique thymic microenvironment for topographically specific development of T cells.

Direct evidence that gamma 1 and gamma 3 switching in human B cells is interleukin-10 dependent

Interleukin-10 (IL-10) has various effects on B cell immunoglobulin (Ig) production. Indirect evidence suggests that IL-10 functions as a switch factor for IgG production. In this study, the switch deleted Ig gene DNA was isolated and characterized, as direct evidence that IL-10 induced isotype switching in human B cells. In addition, 16 chimeric Ig fragments were isolated, representing deleted DNA generated by in vitro isotype switching from mu to gamma in human B cells, following stimulation with IL-10 and anti-CD40 monoclonal antibodies (CD40 mAb). These clones consisted solely of S gamma 1/S mu and S gamma 3/S mu chimeric switch circular DNAs, no S gamma 2/S mu or S gamma 4/S mu switch DNA was observed. In addition, IL-10 alone induced only gamma 1 and gamma 3 germ-line mRNA transcripts, as determined by restriction digestion of the reverse transcription-polymerase chain reaction products. Three modes of mu-gamma 3 isotype switching were detected: (1) direct switching; (2) internal deletion of S mu proceeding mu to gamma 3 switching; and (3) internal deletion of S gamma 3 proceeding mu to gamma 3 switching. These results directly demonstrate that gamma 1 and gamma 3 switching in human B cells is specifically induced by IL-10 in the presence of CD40 mAb.