Direct Expression of the Extracellular Portion of Human FcεRIα Chain as Inclusion Bodies in Escherichia coli

The extracellular portion of the alpha chain of the human high-affinity IgE receptor (FcepsilonRIalpha) was expressed as inclusion bodies in Escherichia coli. In immunoblot analysis, two bands were reactive to human IgE and mouse anti-human FcepsilonRIalpha monoclonal antibodies. N-terminal sequencing showed that the two bands were equivalent to the soluble FcepsilonRIalpha with a methionine residue at the N-terminus (Met-1-172) and 23-172, in which the N-terminal 22 residues of the soluble FcepsilonRIalpha have been removed, possibly by degradation in E. coli cells. IgE-binding to CHO cells expressing FcepsilonRI was inhibited by the addition of the recombinant products prepared by the refolding procedure from inclusion bodies. The system for the expression of soluble human FcepsilonRIalpha in E. coli presented in this study and its further improvement would be useful for the production of the protein as a potent therapeutic and for analysis of the IgE-FcepsilonRIalpha interaction.

The interaction between Lyn and FcεRIβ is indispensable for FcεRI-mediated human mast cell activation

BACKGROUND

FcεRIβ reportedly functions as an amplifier of the FcεRIγ-mediated activation signal using a reconstitution system. However, the amplification mechanisms in human mast cells (MCs) are poorly understood. We previously reported the hyperexpression of FcεRIβ of MCs in giant papillae from vernal keratoconjunctivitis patients, compared with that in conjunctivae from nonallergic conjunctivitis patients. Elucidation of the molecular mechanisms of the amplification induced by FcεRIβ should provide new targets for novel therapeutic interventions. The aim is to understand in greater details the function of FcεRIβ in human MC FcεRI expression and signaling.

METHODS

FcεRIβ and Lyn expression was reduced using a lentiviral shRNA silencing technique. Localization of Lyn and FcεRIβ in cultured MCs was examined by confocal microscopic analysis. Mediators were measured by ELISAs.

RESULTS

The diminution of FcεRIβ significantly downregulated cell surface FcεRI expression and FcεRI-mediated mediator release/production. The downregulation of FcεRI-mediated degranulation was not only due to the decrease in FcεRI expression. The diminution of FcεRIβ inhibited the redistribution of Lyn within the cell membrane following IgE sensitization. The diminution of Lyn in MCs significantly downregulated FcεRI-mediated degranulation. The recombinant cell-penetrating forms of phosphorylated FcεRIβ immunoreceptor tyrosine-based activation motif (ITAM) for intracellular delivery disturbed the interaction between Lyn and phosphorylated endogenous FcεRIβ ITAM, resulted in inhibiting IgE-dependent histamine release from MCs in vitro and from giant papillae specimens ex vivo.

CONCLUSION

The interaction between Lyn and FcεRIβ is indispensable for FcεRI-mediated human MC activation, and specific inhibition of the interaction may represent a new therapeutic strategy for the treatment of human allergic diseases.

Oncology in Cambodia

Cambodia, a country of 14 million inhabitants, was devastated during the Khmer Rouge period and thereafter. The resources of treatment are rare: only one radiotherapy department, renovated in 2003, with an old cobalt machine; few surgeons trained to operate on cancer patients; no hematology; no facilities to use intensive chemotherapy; no nuclear medicine department and no palliative care unit. Cervical cancer incidence is one of the highest in the world, while in men liver cancer ranks first (20% of all male cancers). Cancers are seen at stage 3 or 4 for 70% of patients. There is no prevention program - only a vaccination program against hepatitis B for newborns - and no screening program for cervical cancer or breast cancer. In 2010, oncology, recognized as a full specialty, was created to train the future oncologists on site at the University of Phnom Penh. A new National Cancer Center will be built in 2013 with modern facilities for radiotherapy, medical oncology, hematology and nuclear medicine. Cooperation with foreign countries, especially France, and international organizations has been established and is ongoing. Progress is occurring slowly due to the shortage of money for Cambodian institutions and the lay public.

Molecular epidemiology of Orientia tsutsugamushi in Cambodia and Central Vietnam reveals a broad region-wide genetic diversity

Scrub typhus is an acute infectious disease caused by an obligate intracellular bacterium Orientia tsutsugamushi following the bite of infected trombiculid mites of the genus Leptotrombidium. This zoonotic disease is a major cause of febrile illness in the Asia-Pacific region, with a large spectrum of clinical manifestations from unapparent or mild disease to fatal disease. O. tsutsugamushi is characterized by a very high genomic plasticity and a large number of antigenic variants amongst strains. The 56-kDa type specific antigen (TSA) gene, encoding the major antigenic protein, was used as reference to investigate the genetic relationships between the strains and to genotype O. tsutsugamushi isolates. The open reading frame of the 56-kDa TSA gene of 41 sequences (28 Cambodian and 13 Vietnamese strains) from patient samples were sequenced and used for genotyping. The 28 Cambodian isolates clustered into 5 major groups, including Karp (43.5%), JG-v (25%), Kato/TA716 (21.5%), TA763 (3.5%) and Gilliam (3.5%). Karp (77%), TA763 (15.5%) and JG-v (7.5%) strains were identified amongst the 13 Vietnamese isolates. This is the first countrywide genotyping description in Cambodia and in Central Vietnam. These results demonstrate the considerable diversity of genotypes in co-circulation in both countries. The genotyping result might raise awareness amongst Cambodian and Vietnamese clinicians of the high genetic diversity of circulating O. tsutsugamushi strains and provides unique and beneficial data for serological and molecular diagnosis of scrub typhus infections as well as raw materials for future studies and vaccine development.

FcepsilonRI-mediated thymic stromal lymphopoietin production by interleukin-4-primed human mast cells

A significant increase of mRNA expression of thymic stromal lymphopoietin (TSLP) has been reported in the bronchial mast cells (MCs) of asthmatic subjects; however, the mechanism underlying the upregulation of TSLP mRNA and protein remains unknown. FcepsilonRI-mediated activation of human MCs upregulated TSLP mRNA expression by 5.2+/-2.9-fold, while activation of the MCs using lipopolysaccharide and polyriboinosinic:polyribocytidylic acid failed to upregulate TSLP. Stimulation of MCs with interleukin (IL)-4 alone did not affect the TSLP mRNA expression, while pre-incubation of MCs with IL-4 for 48 h significantly enhanced the FcepsilonRI-mediated TSLP mRNA expression (by 53.7+/-15.9-fold; p<0.05) and the amount of TSLP in the cell pellets increased significantly from 23.4+/-4.3 pg mL(-1) to 121.5+/-3.7 pg mL(-1) (p<0.0001). However, the released TSLP was rapidly degraded by proteases that were released by MCs. We identified the population of cells expressing TSLP in the lungs of 16 asthmatic and 11 control subjects by immunohistochemistry. The percentage of TSLP-positive MCs in the total population of MCs was significantly increased in asthmatic airways (p<0.0001). Thus, MCs are able to store TSLP intracellularly and to produce TSLP following aggregation of FcepsilonRI in the presence of IL-4.

Activation of basophils by stem cell factor: comparison with insulin-like growth factor-I

BACKGROUND

Basophils are an active participant in the pathogenesis of local inflammation in allergic diseases such as asthma, but it is not fully known how basophil activation is regulated in inflamed tissue.

OBJECTIVE

In order to clarify the control mechanisms of basophil activation in chronic inflammation and at remodeling sites, we analyzed the effects of fibroblast-derived cytokines, stem cell factor (SCF), and insulin-like growth factor-I (IGF-I) on basophils.

METHODS

The effects of SCF and IGF-I on degranulation and surface activation marker expression by basophils were assessed and compared.

RESULTS

SCF enhanced human basophil histamine release elicited by some, but not all, secretagogues; degranulation in response to IgE- or FcepsilonRI-mediated stimulation and 12-o-tetradecanoyl-phorbol-13-acetate (TPA) was enhanced by SCF. SCF slightly enhanced ionophore A23187-induced histamine release by basophils from some donors, but it failed to affect the release elicited by monocyte chemoattractant protein-1 (MCP-1), formylmethionyl-leucyl-phenylalanine (FMLP) or C5a. The repertoire of secretagogues responsive to SCF was similar to that of IGF-I. Expression levels of both CD11b and CD69 markers were significantly enhanced by the combination of SCF and IGF-I.

CONCLUSIONS

These results suggest that SCF and IGF-I may modify the activation of basophils in a similar and/or synergistic fashion. Interaction of basophils with these cytokines might be involved in the pathogenesis of local inflammation and the remodeling process in asthma.

Common and distinct signalling cascades in the production of tumour necrosis factor-alpha and interleukin-13 induced by lipopolysaccharide in RBL-2H3 cells

BACKGROUND

Activation of mast cells by lipopolysaccharide (LPS) results in the production of TNF-alpha and IL-13. TNF-alpha and IL-13 are key mediators in the development of neutrophilic and allergic inflammation, respectively. LPS-induced TNF-alpha and IL-13 production in mast cells has been reported to be mediated by Toll-like receptor 4 (TLR4) signalling, but differences in signal transduction mechanisms leading to the production of these cytokines are not clearly defined.

OBJECTIVE

We investigated the molecular mechanisms responsible for LPS-induced TNF-alpha and IL-13 production in mast cells.

METHODS

TNF-alpha and IL-13 production by LPS was assessed by transfecting RBL-2H3 cells with dominant-negative (DN) expression vectors.

RESULTS

Transfection of RBL-2H3 cells with plasmids encoding DN mutants of myeloid differentiation protein (MyD88) and TNFR-associated factor (TRAF6) inhibited both LPS-induced TNF-alpha and IL-13 production. IkappaBalpha-DN inhibited LPS-induced production of TNF-alpha, but not IL-13. We also found that inhibition of p38 kinase suppressed both TNF-alpha and IL-13 induction by LPS, and inhibition of JNK reduced IL-13 production, but not TNF-alpha. Furthermore, we found that protein kinase R (PKR) was activated by LPS in these cells. Treatment with 2-aminopurine, a PKR inhibitor, attenuated LPS-induced nuclear factor-kappaB activation and TNF-alpha production, whereas inhibition of PKR had little effect on IL-13 production.

CONCLUSION

These findings indicate that the production of TNF-alpha and IL-13 by LPS required TLR4/MyD88/TRAF6 signalling as a common pathway of mast cell-mediated inflammation. We furthermore found that TNF-alpha and IL-13 production were differentially regulated by signalling cascades through PKR and mitogen-activated protein kinases downstream of TRAF6 in mast cells.

Dapsone suppresses human neutrophil superoxide production and elastase release in a calcium-dependent manner

BACKGROUND

Dapsone (4,4'-diaminodiphenyl sulphone) is a powerful therapeutic tool in many skin diseases including neutrophilic dermatoses. The drug has an outstanding therapeutic efficacy against many skin diseases characterized by neutrophil-rich infiltrates; however, mechanisms of its action are poorly understood.

OBJECTIVES

We investigated the effects of dapsone on respiratory and secretory functions of human neutrophils triggered by the chemotactic peptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP), the physiological agonist C5a, and phorbol myristate acetate (PMA).

METHODS

Human neutrophils were isolated from venous blood obtained from healthy donors. We detected extracellular production of superoxide (O(2) (-)) by cytochrome C reduction assay, and intracellular production of O(2) (-) by flow cytometry. Neutrophil elastase release was measured by the cleavage of the specific elastase substrate N-methoxysuccinyl-Ala-Ala-Pro-Val-p-nitroanilide. Measurement of cytosolic free calcium concentration was performed using the calcium-reactive fluorescence probe, Fluo-3.

RESULTS

Dapsone suppressed intra- and extracellular production of O(2) (-) and elastase release triggered by fMLP and C5a, but not by PMA. Both fMLP and C5a signalled the above pathways by inducing calcium influx, but PMA functions bypassed calcium influx. Dapsone was capable of antagonizing the induction of calcium influx.

CONCLUSIONS

These findings suggest that one mechanism of the anti-inflammatory action of dapsone is inhibition of calcium-dependent functions of neutrophils including release of tissue-damaging oxidants and proteases in the affected skin.

Monocyte chemoattractant protein (MCP)-1 production via functionally reconstituted Fcalpha receptor (CD89) on glomerular mesangial cells

BACKGROUND

Fc alpha receptor (FcalphaR; CD89) is the receptor for Fc portion of IgA in various cells, and displays various immunological responses on binding. It is important to analyze the mesangial functions via FcalphaR in the pathogenesis of IgA nephropathy. However, it is still controversial whether FcalphaR is expressed on mesangial cells. To assess biological functions of FcalphaR on the mesangial cells, we established mesangial transfectants that expressed FcalphaR with or without FcRgamma chain that is a common signaling molecule of FcRs. The production of monocyte chemoattractant protein-1 (MCP-1) by mesangial cells is known to contribute to cellular infiltration into glomeruli and subsequent glomerular injuries.

METHODS

Murine mesangial cell lines (SV40 MES 13) were transfected with cDNA of the human FcalphaR. Furthermore, we co-transfected some of the FcalphaR transfectants with cDNA of human FcRgamma chain. The tyrosine phosphorylation of the intra-mesangial proteins after FcalphaR cross-linking was examined by immunoprecipitation. MCP-1 production from each transfectant stimulated with heat aggregated IgA was determined by sandwich ELISA.

RESULTS

Two kinds of mesangial transfectants stably expressed human FcalphaR with or without FcRgamma chain (FcalphaR(+), FcalphaR(+)/gamma(+)). Phosphorylation of FcRgamma chain and syk kinase was detected in FcalphaR(+) and FcalphaR(+)/gamma(+) cells, but not in untransfected cells. Aggregated IgA induced significantly higher MCP-1 production in FcalphaR(+)/gamma(+) than those in FcalphaR(+) or untransfected control.

CONCLUSIONS

Present study demonstrated that FcalphaR and FcRgamma chain could be reconstituted in mesangial cells and mediated MCP-1 production by aggregated IgA in a dose-dependent manner. Current data would argue that FcalphaR can be activated in mesangial cells through their own machinery, although underlying mechanisms for FcalphaR induction in mesangial cells remain unclear.

Transforming growth factor-beta1 suppresses atopic dermatitis-like skin lesions in NC/Nga mice

BACKGROUND

Atopic dermatitis is a chronic, relapsing inflammatory disorder characterized by pruritic and eczematous skin lesions. Transforming growth factor (TGF)-beta1 has been implicated in the suppression of inflammatory responses.

OBJECTIVE

The purpose of this study is to determine whether TGF-beta1 suppresses skin lesions in a mouse model of atopic dermatitis.

METHODS

We used the NC/Nga strain of mice as an in vivo model of atopic dermatitis. The effects of exogenous TGF-beta1 on atopic dermatitis-like skin lesions in NC/Nga mice were evaluated clinically, histologically and immunologically.

RESULTS

Subcutaneous injection of recombinant TGF-beta1 macroscopically suppressed eczematous skin lesions in NC/Nga mice associated with reduced serum immunoglobulin E (IgE) levels. Histological analysis showed that TGF-beta1 significantly inhibited the infiltration of inflammatory cells such as mast cells and eosinophils into the skin of NC/Nga mice. Spontaneous interferon (IFN)-gamma production from splenocytes of NC/Nga mice was down-regulated by the treatment with TGF-beta1 and neutralizing antibody against IFN-gamma inhibited skin lesions in NC/Nga mice. The inhibitory effect of TGF-beta1 on the skin lesions lasted at least 1 week after cessation of the treatment.

CONCLUSION

These findings indicate that TGF-beta1 suppressed atopic dermatitis-like skin lesions in NC/Nga mice at least in part through down-regulation of IFN-gamma. These results suggest that TGF-beta1 may have a therapeutic potential for atopic dermatitis.

A comparison of FcepsilonRI-mediated RANTES release from human platelets between allergic patients and healthy individuals

BACKGROUND

Recently some studies have suggested that human platelets may play an important role in allergic inflammation through the high affinity IgE receptor (FcepsilonRI), the low affinity IgE receptor (FcepsilonRII/CD23) and the low affinity IgG receptor (FcgammaRIIA/CD32) expressed on the cell surface. We reported that human platelets via the FcepsilonRI induced the release of the chemical mediator serotonin and the chemokine RANTES (regulated upon activation, normal T expressed and presumably secreted), but the biological implication of human platelets in type I allergy has not yet been understood clearly.

METHODS

We compared the levels of RANTES release from platelets obtained from allergic patients and healthy individuals, stimulated with monoclonal antibody (Ab) to human FcepsilonRI alpha-chain, or human myeloma IgE and anti-human IgE Ab.

RESULTS

We confirmed that the level of RANTES release from platelets of allergic patients stimulated with human IgE and anti-human IgE was significantly higher than that of healthy individuals.

CONCLUSIONS

We demonstrated that the surface expression levels of FcepsilonRI on the platelets from allergic patients and healthy individuals were not significantly different, but that the platelets of allergic patients were more activated by the IgE-FcepsilonRI pathway than those of healthy individuals. Taken together, these results suggest a novel and important role for human platelets in perpetuating allergic inflammation through the IgE and FcepsilonRI.

Establishment and characterization of a murine mast cell line derived from NC/Nga mice

A cell line, termed NCJ, was established from the bone marrow-derived mast cells (BMMCs) of NC/Nga mice that are mouse models for atopic dermatitis. NCJ cells expressed FcepsilonRI and c-kit and showed a metachromasia of the granules with a toluidine blue-positive and safranin-negative staining pattern that is characteristic for immature-type mast cells. Interestingly, NCJ cells showed proliferation independent of IL-3, which was associated with constitutive phosphorylation of Raf-1 and Erk kinases. Although NCJ cells had several characteristics of mast cells, we failed to detect FcepsilonRI-mediated beta-hexosaminidase release and its histamine content. These findings indicated that NCJ cells represented a mast cell line with an immature phenotype and the ability to proliferate in the absence of mast cell growth factors. NCJ cells might thus be useful to study the molecular basis of mast cell proliferation.

[Induction of atopic dermatitis-like skin lesion in NC/Nga mice--the influence of the skin barrier destroying solution to the induction of dermatitis]

NC/Nga mouse is well known as a mouse model for atopic dermatitis. In general, when NC/Nga mouse are raised under specific pathogen free (SPF) conditions no skin lesions are detected, but when under non-filtrated (conventional) condition, atopic dermatitis like skin lesions appear spontaneously. However, this dermatitis develops in 70-90% of mice (not 100%), which makes it difficult to perform reproducible experiments every time. This study was performed under SPF conditions, using the four solutions (2% SDS, 4% SDS, ethanol, acetone/ether) to destroy the skin barrier function, and thereafter, applying the extracted solution of mite: Dermatophagoides pteronyssinus, which is a very popular antigen in pathogenesis of human atopic dermatitis. The extracted solution of mite was applied repeatedly on the NC/Nga mice with a pretreatment of barrier destroying solution and after 8 weeks the mice developed severe dermatitis (clinical skin condition score of 7-10.2 points) with marked elevation of plasma IgE level, whereas mice coated only with the barrier destroying solution showed weak skin lesion with no elevation of plasma IgE level. BALB/c mice, which are employed as control, showed weak skin lesion (clinical skin condition score of 0-3.8 points) and slight elevation of plasma IgE level after repeated application of the extracted solution of mite with a pretreatment of the barrier destroying solution, whereas mice coated only with the barrier destroying solution showed weak skin lesion and the no elevation of plasma IgE level was observed. In this study, using several solutions to disturb the skin barrier function before applying the antigen, we have found a suitable condition and types of solutions in inducing dermatitis in NC/Nga mice.

Variations in the human CC chemokine eotaxin gene

The CC chemokine eotaxin (CCL11) plays a major role in the recruitment and activation of eosinophils in allergic disorders. In the present study, we performed polymorphism screening of the coding and promoter regions of the eotaxin gene (SCYA11). A G to A single nucleotide substitution was detected at position 67, which resulted in a non-conservative amino acid change of Ala at position 23 to Thr (A23T) within the signal peptide. Two single nucleotide substitutions, ie, C to T at position -426 (-426C>T), and A to G at position -384 (-384A>G), were detected in the 5'-flanking regions. Significant linkage disequilibrium was observed between positions -426 and -384, and also between -384 and +67. No significant association was observed between these variations and susceptibility to asthma.

Gene expression profiles for Fc epsilon RI, cytokines and chemokines upon Fc epsilon RI activation in human cultured mast cells derived from peripheral blood

Mast cells have been reported to release not only chemical mediators, but also cytokines upon Fc epsilon receptor I(Fc epsilon RI) cross-linking. Recently, we have established a culture system to derive chymase-rich human mast cells from mononuclear cells in peripheral blood. However, the functional properties of these mast cells have remained unrevealed. In this study, we examined the functions of peripheral blood-derived human cultured mast cells (pHCMCs). pHCMCs expressed functional Fc epsilon RI, and most of them contained tryptase. These pHCMCs sensitized with immunoglobulin E (IgE) and interleukin 4 (IL-4) were activated through cross-linking of Fc epsilon RI. The time-dependent mRNA expression profiles of Fc epsilon RI subunits, cytokines and chemokines in the sensitized pHCMCs upon Fc epsilon RI engagement were examined by reverse transcriptase polymerase chain reaction (RT-PCR). mRNA for most of cytokines and chemokines, which were observed in allergic inflammation, was detected in activated pHCMCs. In addition, gene expression for monocyte chemoattractant protein 3 (MCP-3) in human mast cells, and liver and activation-regulated chemokine (LARC), thymus and activation-regulated chemokine (TARC) and macrophage-derived chemokine (MDC) in mast cells was revealed for the first time in our study. Fc epsilon RI-mediated cytokine and chemokine production at protein level was evaluated using enzyme-linked immunosorbent assay (ELISA). These data suggest that pHCMCs, which are capable of producing a variety of cytokines and chemokines, can be a useful candidate for investigating roles of mast cells as a conductor for allergic inflammation.

Enhanced expression of the high-affinity receptor for IgE (Fc(epsilon)RI) associated with decreased numbers of Langerhans cells in the lesional epidermis of atopic dermatitis

Epidermal Langerhans cells (LCs) and the high-affinity receptor for IgE (Fc(epsilon)RI) on their surface are considered important in the pathogenesis of atopic dermatitis (AD). We investigated the numbers of epidermal LCs and their Fc(epsilon)RI expression in patients with AD and healthy controls. Biopsy specimens taken from lesional skin from 17 patients with AD, non-lesional skin from five patients with AD and normal skin from five healthy individuals were immunohistochemically stained with a monoclonal antibody against CD1a or with either of two monoclonal antibodies against two different epitopes of Fc(epsilon)RI alpha chain. Many dendritic cells were positively stained with anti-CD1a antibody in the epidermis of each skin sample, and fewer cells were stained with anti-Fc(epsilon)RI antibodies. The numbers of epidermal LCs positive for Fc(epsilon)RI were significantly increased in both lesional and non-lesional skin from AD patients compared with those in normal skin, suggesting important roles of Fc(epsilon)RI+LCs in the pathogenesis of the disease. In contrast, the numbers of total epidermal LCs (CD1a-positive) were decreased in AD lesional skin compared with those in non-lesional skin from AD patients and in normal skin from healthy subjects. Together with our finding that the numbers of epidermal LCs were negatively correlated with the clinical severity of the AD lesions, we concluded that epidermal LCs may decrease in some conditions of AD, probably in lesions with severe inflammation.

Identification of Nash1, a novel protein containing a nuclear localization signal, a sterile alpha motif, and an SH3 domain preferentially expressed in mast cells

By using a serial analysis of gene expression (SAGE), we have identified a novel full-length cDNA that is preferentially expressed in human cord blood-derived mast cells. The predicted protein showed unique primary structure with a nuclear localization signal (NLS), a sterile alpha motif (SAM), and a Src homology 3 domain (SH3) (termed Nash1). Nash1 was mapped to human chromosome 21q11.1 and highly expressed in spleen, liver, peripheral blood, and mast cell lines. In consistent with the presence of NLS, Nash1 was localized in the nucleus. Interestingly, screening gene databases for Nash1-related sequences revealed the existence of a Nash1-related gene termed SLY that was preferentially detected in lymphoid cells. We also found at least two additional candidates for this gene family in the database. These findings suggested that Nash1 and Nash1-related proteins consisted of a novel family of signaling/adaptor proteins, and Nash1 might function as a signaling component of mast cells, possibly in the nucleus.

An essential role of angiotensin II receptor type 1a in recipient kidney, not in transplanted peripheral blood leukocytes, in progressive immune-mediated renal injury

Despite an intensive effort of elucidating the pathogenic role of angiotensin II (AII) in immune-mediated renal injury, the precise mechanisms are poorly understood. In the present study, we examined the site of AII action, peripheral blood leukocytes or resident renal cells, in immune-mediated renal injury using AII type 1a receptor (AT1a)-deficient homozygous (AT1a -/-) mice and wild-type (AT1a +/+) mice. The AT1a -/- mice showed delayed-type hypersensitivity similar to that of the AT1a +/+ mice, suggesting that the lack of AT1a does not impair a Th1-type cellular immune response of peripheral blood leukocytes involved in immune-mediated renal injury. We then generated the radiation bone marrow chimera mice, WA and AW, which have transplanted peripheral blood leukocytes from the AT1a +/+ and AT1a -/- mice into the AT1a -/- and AT1a +/+ mice, respectively. As controls, WW and AA, the AT1a +/+ and AT1a -/- mice given bone marrow cells from the AT1a +/+ and AT1a -/- mice, respectively, were generated. Seven days after induction of antiglomerular basement membrane nephritis, glomerulosclerosis observed in the WW mice was markedly ameliorated in the WA mice, but not in the AW mice. In addition, the recruitment of monocytes/macrophages and the expressions of monocyte chemoattractant protein-1 and intercellular adhesion molecule-1 in the glomeruli of the AW and WW mice was evident, but such significant phenotypes were not seen in the WA and AA mice, showing a marked amelioration of renal injury dependent on the host AT1a genotype. These results demonstrate an essential role of AT1a in intrinsic renal cells for progressive immune-mediated renal injury and indicate a beneficial effect of blocking the renin-angiotensin system in the treatment of such diseases.

Protective roles of mast cells against enterobacterial infection are mediated by Toll-like receptor 4

Toll-like receptors (TLRs) are mammalian homologues of the Drosophila Toll receptors and are thought to have roles in innate recognition of bacteria. We demonstrated that TLR 2, 4, 6, and 8 but not TLR5 were expressed on mouse bone marrow-derived mast cells (BMMCs). Using BMMCs from the genetically TLR4-mutated strain C3H/HeJ, we demonstrated that functional TLR4 was required for a full responsiveness of BMMCs to produce inflammatory cytokines (IL-1beta, TNF-alpha, IL-6, and IL-13) by LPS stimulation. TLR4-mediated stimulation of mast cells by LPS was followed by activation of NF-kappaB but not by stress-activated protein kinase/c-Jun NH2-terminal kinase signaling. In addition, in the cecal ligation and puncture-induced acute septic peritonitis model, we demonstrated that genetically mast cell-deficient W/W(v) mice that were reconstituted with TLR4-mutated BMMCs had significantly higher mortality than W/W(v) mice reconstituted with TLR4-intact BMMCs. Higher mortality of TLR4-mutated BMMC-reconstituted W/W(v) mice was well correlated with defective neutrophil recruitment and production of proinflammatory cytokines in the peritoneal cavity. Taken together, these observations provide definitive evidence that mast cells play important roles in exerting the innate immunity by releasing inflammatory cytokines and recruitment of neutrophils after recognition of enterobacteria through TLR4 on mast cells.

Gene expression screening of human mast cells and eosinophils using high-density oligonucleotide probe arrays: abundant expression of major basic protein in mast cells

Mast cells (MCs) and eosinophils are thought to play important roles in evoking allergic inflammation. Cell-type--specific gene expression was screened among 12,000 genes in human MCs and eosinophils with the use of high-density oligonucleotide probe arrays. In comparison with other leukocytes, MCs expressed 140 cell-type--specific transcripts, whereas eosinophils expressed only 34. Among the transcripts for expected MC-specific proteins such as tryptase, major basic protein (MBP), which had been thought to be eosinophil specific, was ranked fourth in terms of amounts of increased MC-specific messenger RNA. Mature eosinophils were almost lacking this transcript. MCs obtained from 4 different sources (ie, lung, skin, adult peripheral blood progenitor--derived and cord blood progenitor--derived MCs, and eosinophils) were found to have high protein levels of MBP in their granules with the use of flow cytometric and confocal laser scanning microscopic analyses. The present finding that MCs can produce abundant MBP is crucial because many reports regarding allergic pathogenesis have been based on earlier findings that MBP was almost unique to eosinophils and not produced by MCs. (Blood. 2001;98:1127-1134)

Regulation of mouse mast cell surface Fc epsilon RI expression by dexamethasone

It is now clear that the mast cell's functional response to IgE-dependent stimulation can be influenced significantly by the level of expression of the high-affinity IgE receptor (Fc epsilon RI) on the cell's surface. Thus, modulation of Fc epsilon RI surface expression represents a potentially important mechanism for regulating mast cell activity in allergic reactions. In this study, we examined whether a glucocorticoid, dexamethasone (DEX), can influence levels of mast cell Fc epsilon RI expression either in the presence or absence of IgE, an up-regulator of the mast cell surface Fc epsilon RI level. In the absence of IgE, DEX decreased the surface Fc epsilon RI levels in mouse peritoneal mast cells, mouse bone marrow-derived cultured mast cells and a mouse mast cell line, Cl.MC/C57.1. Moreover, DEX also partially suppressed the ability of IgE to enhance surface expression of Fc epsilon RI in these cells. Three different glucocorticoids, DEX, methylprednisolone and hydrocortisone, suppressed Fc epsilon RI expression in mast cells, whereas sex steroids, i.e. estradiol, progesterone and testosterone, did not, indicating that the Fc epsilon RI-suppressing effect is glucocorticoid specific. On the other hand, DEX did not affect levels of Fc epsilon RI alpha, beta or gamma mRNA, suggesting that its ability to decrease surface Fc epsilon RI reflects a post-transcriptional mechanism. Finally, DEX-treated mast cells showed a reduced degranulation response to antigenic stimulation through down-regulation of surface Fc epsilon RI expression in addition to DEX-induced changes in downstream signals. These results show that mast cell surface Fc epsilon RI expression is suppressed by glucocorticoids in both the presence and absence of IgE, and suggest that reduction of mast cell surface Fc epsilon RI levels may be one of the favorable anti-allergic actions of glucocorticoids.

Cloning of full-length genomic DNA encoding human FcepsilonRI alpha-chain and its transcriptional regulation

Two novel exons, named exon 1A and exon 2A, were found at 18.4 and 12.6 kb upstream from the exon known as the first exon of human FcepsilonRI alpha-chain gene. Transcription from the promoter present in the upstream of exon 1A was decreased by mutations introduced into the "first intron" between exon 1A and exon 2A, suggesting the presence of an intronic regulatory element in the intron. Consistent with this, electrophoretic mobility shift assay revealed the presence of a nuclear factor which bound the region in FcepsilonRI alpha-chain positive cells.

Production of humanized antibody against human high-affinity IgE receptor in a serum-free culture of CHO cells, and purification of the Fab fragments

We describe the preparation of Fab fragments of a humanized anti-human high-affinity IgE receptor (Fc epsilonRIalpha) antibody potentially useful for treatment of IgE-mediated allergic diseases. IgE-binding capacities of sixteen combinations of light and heavy chains of four recombinant anti-Fc epsilonRIalpha antibodies, chimeric CRA2, humanized CRA2, chimeric CRA4, and humanized CRA4, were compared. A combination in which both chains were of humanized CRA2 had the highest activity. Stable transfectant clones of four kinds of host cells expressing recombinant antibodies were established. CHO-K1 cells were the most productive. Serum-free media suitable for culture of the stable CHO-transfectant clones were screened. The concentration of the humanized CRA2, which the most productive clone secreted into the chosen serum-free medium, was approximately 100 microg/ml. A procedure for the purification of the antibody, papain-digestion, and purification of Fab fragments was established. The highly purified humanized Fab fragments are suitable for use to examine their in vivo activity and immunogenicity in primates.

Regulation of surface FcepsilonRI expression on human eosinophils by IL-4 and IgE

BACKGROUND

Recent studies have demonstrated that eosinophils from allergic patients express low levels of FcepsilonRI on their surface, but the regulatory mechanisms of eosinophil surface FcepsilonRI expression are not fully understood. We investigated whether IL-4 and IgE, which are reported to regulate surface FcepsilonRI expression on human mast cells, are able to affect surface FcepsilonRI expression in normal human eosinophils.

METHODS

Eosinophils purified from peripheral blood were cultured with IL-5 and with or without IL-4 and/or IgE, and surface FcepsilonRI expression was analyzed by flow cytometry using an anti-FcepsilonRI mAb, CRA-1.

RESULTS

Apparent FcepsilonRI expression (approximately 1% of mast cell FcepsilonRI levels) was observed in eosinophils cultured with both IL-4 and IgE. A combination of IL-4 (>or=1 ng/ml) and IgE (>or= 0.5 microg/ml) was necessary for the maximal induction of surface FcepsilonRI expression. In the presence of IL-4 and IgE, eosinophils cultured for 2 days demonstrated low but statistically significant levels of surface FcepsilonRI, which reached a plateau after 7 days of culture. However, cross-linkage of surface FcepsilonRI molecules by CRA-1 or anti-IgE did not induce any eosinophil activation.

CONCLUSIONS

IL-4 and IgE can affect the levels of surface FcepsilonRI on normal human eosinophils. FcepsilonRI expression on eosinophils may be regulated by a mechanism similar to that in mast cells.

Human neutrophils express the high-affinity receptor for immunoglobulin E (Fc epsilon RI): role in asthma

Polymorphonuclear neutrophils (PMNs) are important effector cells in host defense and the inflammatory response to antigen. The involvement of PMNs in inflammation is mediated mainly by the Fc receptor family, including IgE receptors. Recently, PMNs were shown to express two IgE receptors (CD23/Fc epsilon RII and galectin-3). In allergic diseases, the dominant role of IgE has been mainly ascribed to its high-affinity receptor, Fc epsilon RI. We have examined the expression of Fc epsilon RI by PMNS: mRNA and cell surface expression of Fc epsilon RI alpha chain was identified on PMNs from asthmatic subjects. Furthermore, preincubation with human IgE Fc fragment blocks completely the binding of anti-Fc epsilon RI alpha chain (mAb15--1) to human PMNS: Conversely, preincubation of PMNs with mAb15--1 inhibits significantly the binding of IgE Fc fragment to PMNs, indicating that IgE bound to the cell surface of PMNs mainly via the Fc epsilon RI. Peripheral blood and bronchoalveolar lavage (BAL) PMNs from asthmatic subjects also express intracellular Fc epsilon RI alpha and beta chain immunoreactivity. Engagement of Fc epsilon RI induces the release of IL-8 by PMNS: Collectively, these observations provide new evidence that PMNs express the Fc epsilon RI and suggest that these cells may play a role in allergic inflammation through an IgE-dependent activation mechanism.

Blockade of TGF-beta signaling in T cells prevents the development of experimental glomerulonephritis

Anti-glomerular basement membrane (GBM) Ab-induced glomerulonephritis (GN) at late stage is thought to be mediated by T cells. However, signaling pathways of T cells that are involved in the development of anti-GBM Ab-induced GN are unclear. We have recently established transgenic mice expressing Smad7, an inhibitor of TGF-beta signaling, in mature T cells, where signaling by TGF-beta was blocked specifically in T cells. In this study, we showed that anti-GBM Ab-induced GN was suppressed in several measures in the transgenic mice including the severity of glomerular changes, proteinuria, renal function, and CD4 T cell infiltration into the glomeruli without down-regulation of CD62 ligand (CD62L) (L-selectin) expression on CD4 T cells. Furthermore, treatment with the soluble fusion protein of CD62L and IgG enhanced anti-GBM Ab-induced GN. These findings indicated that blockade of TGF-beta signaling in T cells prevented the development of anti-GBM Ab-induced GN. Because CD62L on T cells appears to be inhibitory for the development of anti-GBM Ab-induced GN, persistent expression of CD62L on CD4 T cells may explain, at least in part, the suppression of anti-GBM Ab-induced GN in the transgenic mice. Our findings suggest that the development of anti-GBM Ab-induced GN requires TGF-beta/Smad signaling in T cells.

Selective down-regulation of high-affinity IgE receptor (FcepsilonRI) alpha-chain messenger RNA among transcriptome in cord blood-derived versus adult peripheral blood-derived cultured human mast cells

Substantial numbers of human mast cells (MCs) were generated from umbilical cord blood (CB) and from adult peripheral blood (PB). A single CB progenitor produced 15 436 MCs, whereas a single PB progenitor produced 807 MCs on average. However, PB-derived MCs were far more active than CB-derived MCs in terms of high-affinity IgE receptor (FcepsilonRI)-mediated reactions. One million sensitized PB-derived MCs released 3.6 microg histamine, 215 pg IL-5, and 14 ng granulocyte macrophage-colony-stimulating factor (GM-CSF), whereas 10(6) sensitized CB-derived MCs released only 0.8 microg histamine, 31 pg IL-5, and 0.58 ng GM-CSF on anti-IgE challenge. However, ionophore A23 187 released similar levels of histamine from the 2 MC types. PB-derived MCs highly expressed surface FcepsilonRI alpha chain, and CB-derived MCs almost lacked it in the absence of IgE. PB-derived MCs expressed approximately 5 times higher levels of messenger RNA (mRNA) for FcepsilonRI alpha chain than CB-derived MCs, but mRNAs for beta and gamma chains of the receptors were equally expressed. Among the approximately 5600 kinds of full-length human genes examined by using the high-density oligonucleotide probe-array system, FcepsilonRIalpha was ranked the fifth most increased transcript in PB-derived MCs. The 4 other increased transcripts were unrelated to MC function. These results suggest that IgE-mediated reactions may be restricted during early infancy through the selective inhibition of FcepsilonRIalpha transcription, which is probably committed at progenitor stages and is, at least in part, cytokine-insensitive.

A complex composed of USF1 and USF2 activates the human FcepsilonRI alpha chain expression via a CAGCTG element in the first intron

The high-affinity IgE receptor, FcepsilonRI, is a key regulatory molecule in the allergic reaction. During the course of studies to find cis-acting elements for FcepsilonRI alpha chain gene expression, a CAGCTG sequence located in the first intron was revealed to serve as a crucial enhancer element. Electromobility shift assays using antibodies and in vitro translation products showed that the CAGCTG element was recognized by the USF1/USF2 complex. As was the case for other intronic cis-elements, the CAGCTG element regulated the promoter in an orientation- and position-dependent manner. Overexpression of USF2 antisense repressed the FcepsilonRI alpha chain gene promoter and decreased the amount of alpha chain mRNA in mast cell lines. All these results indicated that the USF1/USF2 complex activates the human FcepsilonRI alpha chain gene expression via the CAGCTG element in the first intron.

Polymorphism in promoter region of Fcalpha receptor gene in patients with IgA nephropathy

We have recently identified two novel polymorphisms (-114T/C and +56T/C relative to the major transcription start site) in the functional promoter region of the Fcalpha receptor (FcalphaR) gene. Since altered FcalphaR expression may be associated with IgA nephropathy, we examined these promoter polymorphisms in this disease. Patients with IgA nephropathy (n = 90), patients with other primary glomerulonephritis (n = 50), and healthy adults (n = 83) were studied. Genotyping was performed by the polymerase chain reaction (PCR) followed by direct sequence analysis and was subsequently confirmed by PCR with mismatched primers followed by restriction fragment length polymorphism analysis. The study demonstrated that the frequency of the +56C allele in patients with IgA nephropathy (0.511) was significantly (P < 0.01) higher than that in patients with other primary glomerulonephritis (0.350) and healthy adults (0.337). In addition, a significant increase in the frequency of the +56CC genotype was observed in patients with IgA nephropathy (27.8% vs 10.0% in other GN and vs 9.6% in healthy adults). In contrast, no significant difference in the frequencies of the +56CC genotype and +56C allele was observed between other primary glomerulonephritis patients and healthy adults. The frequency of the -114CC genotype in patients with IgA nephropathy was significantly increased compared with those in both control groups (15.6% vs 4.0% in other GN and vs 2.4% in healthy adults). Polymorphisms of the FcalphaR promoter region therefore appear to be associated with susceptibility to IgA nephropathy, suggesting the importance of the FcalphaR gene and its expression in this disease.

Expression of humanized Fab fragments that recognize the IgE-binding domain of human Fc(epsilon)RIalpha in COS and CHO cells

Interfering with the binding of IgE to high-affinity IgE receptor alpha chain (Fc(epsilon)RIalpha) is a straightforward strategy for the specific prevention of the IgE-mediated allergic reaction specifically. A Fab fragment (Fab) of a humanized antibody against the membrane proximal IgE-binding domain of human Fc(epsilon)RIalpha inhibits the release of histamine from human basophils. We established an efficient expression system in which to produce directly the humanized anti-human Fc(epsilon)RIalpha Fabs without papain-digestion of the whole antibody. Four Fabs with different C-termini of CH1 were expressed directly in COS-7 cells transfected with expression vectors with or without the Fc gene downstream of a stop codon inserted within the hinge gene. The secretion of Fabs when transfected without the Fc gene was remarkably enhanced compared to that when transfected with the Fc gene. The ability of Fabs to inhibit IgE-Fc(epsilon)RIalpha binding when transfected without the Fc gene was equivalent to that of purified Fab prepared by papain-digestion of the whole antibody. No significant differences among the four Fabs were observed in secretion or activity. Clones of CHO-transfectant cells that secreted the Fabs constitutively were acclimatized to a serum-free medium. Analysis of the binding interface between the Fab and human Fc(epsilon)RIalpha will provide useful information for the design of therapeutic reagents for allergy and asthma.

Molecular cloning of rat USF2 cDNA and characterization of splicing variants

The complete nucleotide sequence of rat USF2 cDNA was determined. In addition to the full length clone (USF2FL), four isoforms (delta1, delta2, delta3, and delta4) suggested to be generated by alternative splicing were isolated. USF2delta1 and delta2 lacked 27 and 67 internal amino acid residues, respectively. USF2delta3 and delta4 lacked most of the entire sequence but encoded short peptides of an N-terminal portion of USF2FL. Overexpression of USF2FL increased the transcription of the human high affinity IgE receptor (FcepsilonRI) alpha chain gene through specific binding to the CAGCTG motif in the first intron. On the other hand, overexpression of USF2delta1 or delta2 reduced the transcription of the human FcepsilonRI alpha chain gene. Both USF2FL and USF2delta1 bound to CACGTG as well as CAGCTG, while USF2delta2 bound to CACGTG but not to CAGCTG. These results suggested the presence of a different and definitive role of each variant in the expression of the alpha chain gene.

Inhibition of IgE-dependent histamine release from human peripheral blood basophils by humanized Fab fragments that recognize the membrane proximal domain of the human Fc epsilon RI alpha-chain

BACKGROUND

Inhibition of the interaction between IgE and the alpha-chain of Fc epsilon RI (Fc epsilon RI alpha) is a straightforward strategy to develop therapeutic reagents for IgE-mediated allergic diseases.

OBJECTIVE

The purpose of this study is the humanization of CRA2 and/or CRA4, mouse anti-human Fc epsilon RI alpha monoclonal antibodies (mAbs) which recognize the IgE-binding membrane proximal immunoglobulin-like domain of Fc epsilon RI alpha.

METHODS

The two mAbs were humanized by CDR grafting onto human V region frameworks encoded by human germline V and J genes. The activities of the recombinant antibodies to bind Fc epsilon RI alpha and inhibit IgE binding to Fc epsilon RI alpha were analyzed by flow cytometry and ELISA. Human peripheral blood basophils were pretreated with the Fab fragments of the humanized CRA2 and stimulated with IgE and an anti-IgE polyclonal antibody. The released histamine was measured.

RESULTS

The humanized CRA2 had almost the same activities of binding and inhibition of IgE binding to Fc epsilon RI alpha as the original mouse CRA2. Although the Fc epsilon RI-binding activity was maintained following humanization of the CRA4 light chain V region, it was lost by the humanization of the CRA4 heavy chain V region. Pretreatment of human peripheral blood basophils with the Fab fragments of the humanized CRA2 inhibited their subsequent degranulation activated by cross-linking of the Fc epsilon RI.

CONCLUSION

In the humanized CRA2, all amino acid residues except CDR are replaced with the residues encoded by human germline genes. The humanization of CRA2 might be an important step in the development of immunotherapy to manipulate the IgE network in which mast cells, basophils, and various types of Fc epsilon RI alpha expressing cells are involved.

Splice isoforms of transcription factor Elf-1 affecting its regulatory function in transcription-molecular cloning of rat Elf-1

To elucidate the role of Elf-1 in Fc epsilonRI alpha chain expression, rat Elf-1 cDNAs were isolated and characterized. The rat Elf-1 cDNA of 2744 bp contained an open reading frame of 1848 bp. In addition to the full length rat Elf-1 cDNA (named type 1), two splice isoforms were isolated. One of the two isoforms lacked the amino acid residues from 85th to 120th (type 2), and the other from 85th to 175th (type 3). Similar isoforms were also observed in human tissue. Overexpression of rat Elf-1 (type 1) using a transient coexpression system inhibited of the alpha chain promoter activity. The inhibition activity was different between the isoforms; the inhibition activity of type 2 was lower than that of type 1, and type 3 did not have an inhibitory effect. This observation suggested that each Elf-1 isoform played a different role in the gene expression under its control.

Distinct aggregation of beta- and gamma-chains of the high-affinity IgE receptor on cross-linking

The high-affinity IgE receptor (FcepsilonRI) on mast cells and basophils consists of a ligand-binding alpha-chain and two kinds of signaling chains, a beta-chain and disulfide-linked homodimeric gamma-chains. Crosslinking by multivalent antigen results in the aggregation of the bound IgE/alpha-chain complexes at the cell surface, triggering cell activation, and subsequent internalization through coated pits. However, the precise topographical alterations of the signaling beta- and gamma-chains during stimulation remain unclarified despite their importance in ligand binding/signaling coupling. Here we describe the dynamics of FcepsilonRI subunit distribution in rat basophilic leukemia cells during stimulation as revealed by immunofluorescence and immunogold electron microscopy. Immunolocalization of beta- and gamma-chains was homogeneously distributed on the cell surfaces before stimulation, while crosslinking with multivalent antigen, which elicited optimal degranulation, caused a distinct aggregation of these signaling chains on the cell membrane. Moreover, only gamma- but not beta-chains were aggregated during the stimulation that evoked suboptimal secretion. These findings suggest that high-affinity IgE receptor beta- and gamma-chains do not co-aggregate but for the most part form homogenous aggregates of beta-chains or gamma-chains after crosslinking.

Production of humanized Fab fragment against human high affinity IgE receptor in Pichia pastoris

Binding of allergen-IgE complexes to the high affinity IgE receptor (Fc epsilonRI) on mast cells and basophils leads to the release of various mediaters such as histamine. Fab fragments prepared by the papain digestion of humanized antibody against human Fc epsilonRI inhibited the release of histamine from human basophils. Here we established an expression system to directly produce Fab fragments of the humanized anti-human Fc epsilonRI antibody in methylotropic yeast, P. pastoris. Fab fragments were efficiently secreted into the medium at a concentration of 10-40 mg/L using a signal sequence from the P. pastoris phosphatase gene. They were consisted of disulfide-linked light and heavy chains correctly starting from the first amino acid residues by proper cleavage of the signal peptides. The obtained Fab fragments inhibited the binding between IgE and Fc epsilonRI as efficiently as the counterpart prepared by papain digestion of the whole antibody.

Identification and characterization of the promoter for the gene encoding the human myeloid IgA Fc receptor (FcalphaR, CD89)

The Fc receptor for IgA (FcalphaR, CD89), a transmembrane glycoprotein, is expressed exclusively on human phagocytic cells including monocytes, macrophages, eosinophils, and neutrophils, and is capable of triggering various effector functions. In the present study, we identified and characterized, for the first time, the FcalphaR promoter. A 929-bp fragment of FcalphaR 5'-flanking sequence directed expression of a reporter gene specifically in monocytic cell line U937. Deletion analyses localized element(s) directing tissue-specific reporter gene expression to the 259 bp proximal to the translation initiation site. Within the region, the sequence between 59 and 197 bp downstream of the major transcription start site was shown to be essential for promoter activity. This sequence contains multiple potential binding sites for transcription factors which have been reported to function in myeloid-specific gene expression, including three CCAAT enhancer-binding protein (C/EBP)-binding sites, an NF-kappaB-binding site, an Spl site, an Ets family protein consensus-binding site, and a Myb-binding site. In addition, we identified two polymorphisms (C-->T transition) at the positions 114 bp upstream and 56 bp downstream of the major transcription start site, and demonstrated that the FcalphaR promoter region carrying both the -114T and +56T alleles had significantly lower promoter activity than that harboring the C alleles at both sites. Characterization of this promoter will facilitate further analyses of activation stimuli and transcription factors involved in FcalphaR-mediated immune system, and provide new insights into the mechanism(s) underlying altered FcalphaR expression associated with diseases such as allergic diseaes and IgA nephropathy.

Epitope analysis and primary structures of variable regions of anti-human FcepsilonRI monoclonal antibodies, and expression of the chimeric antibodies fused with human constant regions

The structural analysis of monoclonal antibodies (mAbs) against the alpha subunit of the high affinity IgE receptor (FcepsilonRIalpha) is an alternative approach to obtaining information for the design of inhibitors that will block complementary interaction between IgE and FcepsilonRIalpha and to analyzing the various biological effects induced by anti-FcepsilonRIalpha autoantibodies in chronic urticaria. In this study, epitopes for mouse anti-human FcepsilonRIalpha mAbs and primary structures of variable regions of the mAbs were analyzed. Three mAbs inhibitory for IgE-binding reacted to the deletion mutants of FcepsilonRIalpha containing the whole second immunoglobulin-like domain as well as IgE did. On the other hand, two uninhibitory mAbs reacted to those containing the whole first immunoglobulin-like domain. The cDNAs for variable regions of the five mAbs were cloned and sequenced. Two inhibitory mouse/human chimeric antibodies were expressed in COS7 cells and bound to Chinese hamster ovary transfectant cells expressing FcepsilonRI (CHO/alphabetagamma), and these inhibited the binding of IgE to CHO/alphabetagamma cells.

Blockade of transforming growth factor beta/Smad signaling in T cells by overexpression of Smad7 enhances antigen-induced airway inflammation and airway reactivity

Transforming growth factor (TGF)-beta has been implicated in immunosuppression. However, it remains obscure whether regulation of T cells by TGF-beta contributes to the immunosuppression in vivo. To address this issue, we developed transgenic mice expressing Smad7, an intracellular antagonist of TGF-beta/Smad signaling, selectively in mature T cells using a plasmid construct coding a promoter element (the distal lck promoter) that directs high expression in peripheral T cells. Peripheral T cells were not growth inhibited by TGF-beta in Smad7 transgenic mice. Although Smad7 transgenic mice did not spontaneously show a specific phenotype, antigen-induced airway inflammation and airway reactivity were enhanced in Smad7 transgenic mice associated with high production of both T helper cell type 1 (Th1) and Th2 cytokines. Thus, blockade of TGF-beta/Smad signaling in mature T cells by expression of Smad7 enhanced airway inflammation and airway reactivity, suggesting that regulation of T cells by TGF-beta was crucial for negative regulation of the inflammatory (immune) response. Our findings also implicated TGF-beta/Smad signaling in mature T cells as a regulatory component of allergic asthma.

Polymorphisms in FcepsilonRI beta chain do not affect IgE-mediated mast cell activation

Genetic polyymorphisms that result in three amino acid changes in FcepsilonRI beta chain (Ile(181)-->Leu, Val(183)-->Leu, and Glu(237)-->Gly) have been identified as candidates that associate with allergic disorders such as atopy and asthma. To elucidate the biological significance of these polymorphisms in regulating the expression and function of FcepsilonRI, we generated four types of transfectants that express wild-type or mutant mouse beta chains corresponding to these human variants by retrovirus-mediated gene transfer into beta chain-deficient mouse-derived mast cells. No significant functional differences between the wild-type beta chain transfectant and any of the mutant beta chain transfectants were observed in beta-hexosaminidase release, intracellular calcium mobilization, or cytokine and leukotriene C(4) production in response to FcepsilonRI crosslinking. Our results suggest that these polymorphisms in FcepsilonRI beta chain do not affect FcepsilonRI-mediated mast cell activation at least in our mouse in vitro system.

Reciprocal regulation of cultured human mast cell cytokine production by IL-4 and IFN-gamma

BACKGROUND

T(H)1 and T(H)2 cytokines are thought to regulate allergic inflammation.

OBJECTIVE

Two key regulatory cytokines, IL-4 and IFN-gamma, were examined for their effects on cytokine production by cultured human mast cells (CHMCs).

METHODS

CHMCs were obtained by culturing cord blood-derived CD34(+) cells in the presence of stem cell factor and IL-6 for 14 to 16 weeks. CHMCs were passively sensitized with human myeloma IgE and supplemented with or without IL-4 or IFN-gamma. After the sensitization, CHMCs were stimulated with anti-FcepsilonRIalpha mAb. Concentrations of secreted cytokines were measured by using ELISA, and cytokine messenger RNA was analyzed by using quantitative competitive RT-PCR.

RESULTS

IL-4 profoundly enhanced FcepsilonRI-mediated production of macrophage inflammatory protein (MIP) 1alpha, IL-8, and GM-CSF. For example, the enhancement by IL-4 (10 ng/mL) of the production of MIP-1alpha, IL-8, and GM-CSF was 25-, 7-, and 90-fold, respectively, after 6 hours. IL-4 also enhanced levels of FcepsilonRI-induced cytokine messenger RNA but to a lesser degree. In contrast, IFN-gamma inhibited FcepsilonRI-induced production of MIP-1alpha, IL-8, and GM-CSF. For example, the inhibition by IFN-gamma (10 ng/mL) of FcepsilonRI-mediated production of MIP-1alpha, IL-8, and GM-CSF was 80%, 75%, and 95%, respectively. IFN-gamma also suppressed FcepsilonRI-induced messenger RNA expression of these cytokines. Neither IL-4 nor IFN-gamma affected the kinetics of cytokine production by CHMCs.

CONCLUSION

These data suggest that IL-4 and IFN-gamma may influence allergic reactions by modulating human mast cell cytokine production.

Kinetic analysis of the interaction between recombinant human Fc(epsilon)RIalpha and serum IgEs from allergic patients

Binding of IgE to the high-affinity IgE receptor (Fc(epsilon)RI) is the essential event for allergic reaction. Although there are many reports on binding kinetics between myeloma IgE and Fc(epsilon)RI, little is known about the kinetics between heterogeneous polyclonal IgE in the serum and Fc(epsilon)RIalpha. To elucidate the binding characteristics of heterogeneous serum IgE, we measured kinetic parameters of binding between IgE from allergic patients and a recombinant ectodomain of the human Fc(epsilon)RIalpha subunit by real-time interaction analysis based on surface plasmon resonance. Purified IgE monomer from the plasma of allergic patients displayed kinetics for the interaction with Fc(epsilon)RIalpha similar to those of myeloma IgE. In the case of crude IgE samples from allergic patients, one of seven specimens showed significantly higher affinity than highly purified IgE, suggesting that it is possible for IgEs in this specimen to form complexes of higher molecular weight.

DNA induces apoptosis in electroporated human promonocytic cell line U937

Experimental gene transfer has permitted a wide variety of studies on gene regulation and function. However, possible effects of the introduced DNA on cellular metabolism are not well understood. Here we demonstrated that introduction of DNA into a promonocytic cell line, U937, by electroporation caused extensive cell death. The toxicity of DNA was concentration-dependent. Various DNAs including plasmid and genomic DNAs all caused cell death, indicating that the toxicity is nucleotide sequence-independent. DNA-induced cell death was associated with internucleosomal DNA fragmentation, a decrease in cell size, and a considerable proportion of cells outside cell cycle. From these results, we concluded that cells died by apoptosis. Our findings have experimental implication for an important issue concerning the interpretation of experiments using gene transfer. In addition, we propose that our observed phenomenon may be relevant to an important immune defense mechanism in monocytes/macrophages that facilitates a response to certain viral infections.

A BASH/SLP-76-related adaptor protein MIST/Clnk involved in IgE receptor-mediated mast cell degranulation

Cross-linking of the high-affinity IgE receptor (FcepsilonRI) on mast cells by IgE-antigen complex triggers signal transduction cascades leading to the release of inflammatory mediators and production of cytokines, which are critical for the development of allergic reactions. We have identified a novel member of the BASH/SLP-76 immunoreceptor-coupled adaptor family expressed in mast cells, termed MIST (for mast cell immunoreceptor signal transducer), which has later been found to be identical to a recently reported cytokine-dependent hemopoietic cell linker, Clnk. Upon FcepsilonRI cross-linking, MIST/Clnk is tyrosine phosphorylated and associates with signaling proteins, phospholipase Cgamma, Vav, Grb2 and linker for activation of T cells (LAT). Overexpression of a mutant form of MIST/Clnk inhibited FcepsilonRI-mediated degranulation, increase in intracellular Ca(2+), NF-AT activation and phosphorylation of LAT. As a crucial signaling component for FcepsilonRI-induced mast cell degranulation, MIST/Clnk might serve as a target for anti-allergic therapy.

Sequential requirements of the N-terminal palmitoylation site and SH2 domain of Src family kinases in the initiation and progression of FcepsilonRI signaling

Initial biochemical signaling originating from high-affinity immunoglobulin E receptor (FcepsilonRI) has been ascribed to Src family kinases. To understand the mechanisms by which individual kinases drive the signaling, we conducted reconstitution experiments: FcepsilonRI signaling in RBL2H3 cells was first suppressed by a membrane-anchored, gain-of-function C-terminal Src kinase and then reconstructed with Src family kinases whose C-terminal negative regulatory sequence was replaced with a c-myc epitope. Those constructs derived from Lyn and Fyn, which are associated with detergent-resistant membranes (DRMs), physically interacted with resting FcepsilonRI and reconstructed clustering-induced signaling that leads to calcium mobilization and ERK1 and -2 activation. c-Src-derived construct, which was excluded from DRMs, failed to interact with FcepsilonRI and to restore the signaling, whereas creation of palmitoylatable Cys3 enabled it to interact with DRMs and with FcepsilonRI and to restore the signaling. Deletion of Src homology 3 (SH3) domain from the Lyn-derived construct did not alter its ability to transduce the series of signaling. Deletion of SH2 domain did not affect its association with DRMs and with FcepsilonRI nor clustering-induced tyrosine phosphorylation of FcepsilonRI beta and gamma subunits, but it almost abrogated the next step of tyrosine phosphorylation of Syk and its recruitment to FcepsilonRI. These findings suggest that Lyn and Fyn could, but c-Src could not, drive FcepsilonRI signaling and that N-terminal palmitoylation and SH2 domain are required in sequence for the initial interaction with FcepsilonRI and for the signal progression to the molecular assembly.