Enumeration of IgE secreting B cells. A filter spot-ELISA

Clonal evolution and stereotyped sequences of human IgE lineages in aeroallergen-specific immunotherapy

BACKGROUND

Allergic disease reflects specific inflammatory processes initiated by interaction between allergen and allergen-specific IgE. Specific immunotherapy (SIT) is an effective long-term treatment option, but the mechanisms by which SIT provides desensitization are not well understood.

OBJECTIVE

Our aim was to characterize IgE sequences expressed by allergen-specific B cells over a 3-year longitudinal study of patients with aeroallergies who were undergoing SIT.

METHODS

Allergen-specific IgE-expressing clones were identified by using combinatorial single-chain variable fragment libraries and tracked in PBMCs and nasal biopsy samples over a 3-year period with antibody gene repertoire sequencing. The characteristics of private IgE-expressing clones were compared with those of stereotyped or "public" IgE responses to the grass pollen allergen Phleum pratense (Phl p) 2.

RESULT

Members of the same allergen-specific IgE lineages were observed in nasal biopsy samples and blood, and lineages detected at baseline persisted in blood and nasal biopsy samples after 3 years of SIT, including B cells that express IgE. Evidence of progressive class switch recombination to IgG subclasses was observed after 3 years of SIT. A common stereotyped Phl p 2-specific antibody heavy chain sequence was detected in multiple donors. The amino acid residues enriched in IgE-stereotyped sequences from seropositive donors were analyzed with machine learning and k-mer motif discovery. Stereotyped IgE sequences had lower overall rates of somatic hypermutation and antigen selection than did single-chain variable fragment-derived allergen-specific sequences or IgE sequences of unknown specificity.

CONCLUSION

Longitudinal tracking of rare circulating and tissue-resident allergen-specific IgE+ clones demonstrates persistence of allergen-specific IgE+ clones, progressive class switch recombination to IgG subtypes, and distinct maturation of a stereotyped Phl p 2 clonotype.

Biosensors for Detecting Lymphocytes and Immunoglobulins

Lymphocytes (B, T and natural killer cells) and immunoglobulins are essential for the adaptive immune response against external pathogens. Flow cytometry and enzyme-linked immunosorbent (ELISA) kits are the gold standards to detect immunoglobulins, B cells and T cells, whereas the impedance measurement is the most used technique for natural killer cells. For point-of-care, fast and low-cost devices, biosensors could be suitable for the reliable, stable and reproducible detection of immunoglobulins and lymphocytes. In the literature, such biosensors are commonly fabricated using antibodies, aptamers, proteins and nanomaterials, whereas electrochemical, optical and piezoelectric techniques are used for detection. This review describes how these measurement techniques and transducers can be used to fabricate biosensors for detecting lymphocytes and the total content of immunoglobulins. The various methods and configurations are reported, along with the advantages and current limitations.

Immature B cells preferentially switch to IgE with increased direct Sμ to Sε recombination

To be added.

Immunoglobulin heavy chain (IgH) class-switch recombination (CSR) replaces initially expressed Cμ (IgM) constant regions (C_H) exons with downstream C_H exons. Stimulation of B cells with anti-CD40 plus interleukin-4 induces CSR from Cμ to Cγ1 (IgG1) and Cε (IgE), the latter of which contributes to the pathogenesis of atopic diseases. Although Cε CSR can occur directly from Cμ, most mature peripheral B cells undergo CSR to Cε indirectly, namely from Cμ to Cγ1, and subsequently to Cε. Physiological mechanisms that influence CSR to Cγ1 versus Cε are incompletely understood. In this study, we report a role for B cell developmental maturity in IgE CSR. Based in part on a novel flow cytometric IgE CSR assay, we show that immature B cells preferentially switch to IgE versus IgG1 through a mechanism involving increased direct CSR from Cμ to Cε. Our findings suggest that IgE dysregulation in certain immunodeficiencies may be related to impaired B cell maturation.

IgE regulates T helper cell differentiation through FcgammaRIII mediated dendritic cell cytokine modulation

Asthma and allergy are characterized by dysregulation of inflammatory responses toward Th2 responses and high serum levels of IgE. IgE plays a role in the effector phase by triggering the degranulation of mast cells after antigen-crosslinking but its role in the induction of helper T cell differentiation is unknown. We have previously shown lymphotoxin is required for maintaining physiological levels of serum IgE which minimize spontaneous Th1-mediated airway inflammation, suggesting a physiological role for IgE in the regulation of T helper cell differentiation. We describe the mechanism in which IgE modulates inflammation by regulating dendritic cell cytokine production. Physiological levels of IgE suppress IL-12 production in the spleen and lung, suggesting IgE limits Th1 responses in vivo. IgE directly stimulates dendritic cells through FcgammaRIII to suppress IL-12 in vitro and influences APC to skew CD4+ T cells toward Th2 differentiation. We demonstrate a novel role for IgE in regulating differentiation of adaptive inflammatory responses through direct interaction with FcgammaRIII on dendritic cells.

Modification of Cepsilon mRNA expression by EBV-encoded latent membrane protein 1

To evaluate the effect of expression of latent membrane protein (LMP) 1 encoded by Epstein-Barr virus (EBV) on Cɛ mRNA expression, mRNA levels were examined by RT-PCR or Northern blot analysis upon transient transfection of LMP1 in the splenocytes derived from Brown-Norway rats with or without immunization with 2,4-dinitrophenyl-conjugated Ascaris suum antigen. Splenocytes were transfected with LMP1 expression vector, pSG5-LMP1, using lipofection method. Cɛ mRNA levels were considerably increased by transfection with pSG5-LMP1 in the splenocytes derived from the nonimmunized rats; however, Cɛ mRNA levels were decreased in the splenocytes derived from the immunized rats. Cɛ mRNA expression in IgE-producing cells are modulated by LMP1, which might depend on the differentiation status of B cells upon exposure to allergen.

Involvement of Epstein-Barr virus (EBV)-encoded latent membrane protein (LMP)-1 in the potentiation of C epsilon mRNA expression in human tonsil-derived cells

The aim of our study was to investigate a possible correlation between Epstein-Barr virus (EBV) infection status, including its latent gene expression, and expression of allergy-related genes in human tonsil-derived cells. In the tonsil-derived cells from the patients undergoing routine tonsillectomies for palatine tonsil hypertrophy or tonsillar focal infection, the presence of EBV DNA and mRNA expressions of latent membrane protein (LMP)-1, C epsilon chain, and activation-induced cytidine deaminase (AID) were detected by PCR and RT-PCR analysis, respectively. Of all the 12 patients, PCR products amplified from EBV DNA BamHI W fragment were detected in the tonsils from the 10 patients (83.3%). LMP1 mRNA expressions were confirmed in the six patients (50%). Both LMP1 mRNA expressions and EBV DNA were detected in the five patients. EBV DNA, but not LMP1 mRNA expression, was detected in the five patients. LMP1 mRNA expression, but not EBV DNA, was detected in one patient. In one patient, neither EBV DNA nor LMP1 mRNA expression was confirmed. C epsilon mRNA expressions were confirmed in all the 12 patients along with AID mRNA expressions. The degree of C epsilon mRNA expression, however, varied with the patients. The Fisher's exact probability test revealed a statistically significant correlation between LMP1 and C epsilon gene expressions, indicating that C epsilon mRNA expression level was significantly higher in the LMP1 positive samples than in the negative samples. On the other hand, there was no significant correlation between AID and LMP1 mRNA expressions. Thus, EBV infection is a notable factor capable of exacerbating allergic inflammation.

Mechanisms of eosinophil cytokine release

Human eosinophils have been demonstrated to contain a multitude of cytokines and chemokines that exist pre-formed within these cells. This content of pre-formed cytokines, with diverse potential biologic activities, provides eosinophils with capabilities distinct from most other leukocytes. The localization of pre-formed cytokines within eosinophils is both within specific granules and associated with substantial numbers of morphologically distinct cytoplasmic vesicles. Stimulation for release of specific cytokines, such as IL-4, leads to a regulated signal transduction cascade, which is dependent on the formation of leukotriene C4 within eosinophils where it acts as an intracrine mediator. IL-4 release occurs selectively and is by means of vesicular transport. The capabilities of eosinophils not only to rapidly release pre-formed cytokines but also to differentially regulate which cytokines are released endow eosinophils with distinct abilities in innate and acquired immunity.

Allergen drives class switching to IgE in the nasal mucosa in allergic rhinitis

IgE-expressing B cells are over 1000 times more frequent in the nasal B cell than the peripheral blood B cell population. We have investigated the provenance of these B cells in the nasal mucosa in allergic rhinitis. It is generally accepted that expression of activation-induced cytidine deaminase and class switch recombination (CSR) occur in lymphoid tissue, implying that IgE-committed B cells must migrate through the circulation to the nasal mucosa. Our detection of mRNA for activation-induced cytidine, multiple germline gene transcripts, and epsilon circle transcripts in the nasal mucosa of allergic, in contrast to nonallergic control subjects, however, indicates that local CSR occurs in allergic rhinitis. The germline gene transcripts and epsilon circle transcripts in grass pollen-allergic subjects are up-regulated during the season and also when biopsies from allergic subjects are incubated with the allergen ex vivo. These results demonstrate that allergen stimulates local CSR to IgE, revealing a potential target for topical therapies in allergic rhinitis.

EliCell assay for the detection of released cytokines from eosinophils

Eosinophils contain several preformed cytokines within their specific granules. Therefore, without requiring them in de novo synthesis of cytokines, eosinophils can release quantities of granule-derived cytokines by highly regulated mechanisms. However, eosinophil "degranulation" is poorly understood, in part, because available methodologies did not appear appropriate for analyzing vesicular mobilization and transport of eosinophil granular contents. The EliCell assay is a microscopic methodology substantially modified from other techniques employed to detect cytokine release (i.e., ELISPOT). The method is a dual antibody capture/detection system in which viable eosinophils are incubated in a solid streptavidin-conjugated agarose matrix, which contains a biotinylated capture antibody against the cytokine of interest. Released cytokine is detected around non-permeabilized eosinophils with a separate fluorochrome-labeled detection antibody. Thus, the EliCell system captures and detects extracellular cytokines at the site of their release from eosinophils. As examples, we have used EliCell essays to detect the selective release of either IL-4 or IL-12 cytokines found preformed in eosinophils-from eotaxin- or anti-CD9-stimulated eosinophils, respectively. With appropriate pairs of antibodies, any preformed cytokine found into eosinophil granules could be studied and the mechanisms of their secretion evaluated by using the EliCell assay.

Detection and characterization of plasma cells in peripheral blood: correlation of IgE+ plasma cell frequency with IgE serum titre

In atopic patients and patients with hyper-IgE syndrome (HIE) highly elevated IgE serum levels can be detected. Due to their very low frequency little is known about IgE-producing plasma cells (PC) in peripheral blood. We used CD138 MACS microbeads to enrich plasma cells from peripheral blood of normal donors, atopic patients and one HIE patient. CD138+ cells were mainly CD45+, CD44++, CD19dim, CD38++, CD27++, CD86+, HLA-DR+/++, CD71dim, VLA-4+, VLA-5-, CD28-, CD25-, CD69-, CLA-, CD20-, CD21- and CD22-. They show weak expression of surface Ig but high levels of intracellular Ig and they secrete Ig in culture. Thus CD138+ cells from peripheral blood show characteristics of early plasma cells. IgE+ CD138+ plasma cells could be detected in 19 of 24 normal donors with an average frequency of 0.06% IgE+ cells among CD138+ cells. Higher frequencies were detected in atopic patients, atopic patients with markedly elevated serum IgE levels and the hyper-IgE patient with an average of 0.32%, 7.21% and 6.54%, respectively. Additionally, using the recently developed cellular affinity matrix technology, we were able to detect IgE secreting plasma cells and thereby could demonstrate that most of the IgE secreting cells express CD138. The frequency of IgE+ CD138+ cells among PBMC correlated highly significantly with serum IgE titres (r = 0.8532***), indicating that IgE secreting CD138+ cells in peripheral blood are directly related to the plasma cell pool contributing to the IgE titre.

EliCell: a gel-phase dual antibody capture and detection assay to measure cytokine release from eosinophils

Eosinophils contain many preformed cytokines and chemokines, which are stored in specific granules along with cationic granule proteins. Mobilization and release of these granule contents can be selective and mediated by vesicular transport. We have developed a sensitive method to detect and quantitate eosinophil vesicular transport-mediated release of specific eosinophil proteins. Our EliCell assay is based on microscopic observations of individual viable eosinophils embedded in an agarose matrix that contains immobilized antibody to the protein of interest. Following stimulation of eosinophils, released protein is bound by the capture antibody at its site of release and is detected by a fluorochrome-conjugated detection antibody. We have validated this assay by evaluating interferon-gamma-induced release of RANTES from eosinophils. Extracellularly released RANTES was visualized as focal immunoflourescent staining and was quantitated by scoring the numbers of eosinophils releasing RANTES and by measuring the fluorescent intensity over individual eosinophils. In comparison with ELISA assays of RANTES released into supernatant fluids by interferon-gamma-stimulated eosinophils, EliCell assays were more sensitive enabling detection of RANTES release at earlier times and at lower levels of interferon-gamma stimulation. The EliCell assay provides a sensitive method to study the regulated release of eosinophil-derived cytokines, chemokines and other granule proteins.

Effect of topical fluticasone propionate on the mucosal allergic response induced by ragweed allergen and diesel exhaust particle challenge

Glucocorticoids block the local allergic response in a variety of ways. However, studies have also shown that glucocorticoids increase in vitro IgE synthesis and that treatment with corticosteroids may result in elevated serum IgE concentrations. The ability of topical glucocorticoids to modulate the mucosal IgE response has not been elucidated. We studied the effect of topical steroid (fluticasone propionate) treatment on the local allergic antibody response induced by challenge with either allergen or diesel exhaust particles (DEP). A parallel group study was performed with ragweed-allergic subjects, each subject serving as his/her own control. Nasal provocation challenges were performed on three groups. One group received ragweed allergen, another diesel exhaust particles, and the third saline. The study was repeated following 1 week of treatment with intranasal fluticasone propionate. Each group received the same challenge as before. The concentrations of total immunoglobulins (IgE, IgG, IgA, and IgM), anti-ragweed antibody, IgE- and IgA-secreting cells, epsilon (epsilon) mRNA, and cytokine mRNAs (IL-2, -4, -5, -6, TNF-alpha, INF-gamma) were measured in nasal lavages performed before and at various time points after challenge. Treatment with fluticasone propionate for 7 days caused a decrease in the concentrations of nasal IgE protein, IgE-producing cells, total epsilon mRNA, and all the cytokine mRNAs tested. Furthermore, treatment with fluticasone propionate inhibited the production of allergen-specific IgE and cytokine mRNAs following challenge with ragweed antigen. However, fluticasone treatment did not significantly inhibit the enhancement of mucosal IgE production or cytokine mRNAs observed following nasal challenge with DEP. These results indicate that 1-week treatment with topical fluticasone propionate was effective in blocking local effects of allergen exposure but was unable to inhibit the adjuvant-like effect of DEP.

Plasma IgE levels, activation marker expression, and cytokine production in non-atopic individuals

BACKGROUND

Since human IgE serum levels are very low compared with the other immunoglobulin isotypes, most studies have examined the regulation of IgE production in severely atopic individuals where serum IgE levels are increased. Since atopy is a pathologic consequence of increased IgE production, this disease state could have other influences that result in abnormal expression of these parameters and may not reflect normal IgE regulatory mechanisms.

OBJECTIVE

To study nonatopic individuals to examine the expression of IgE regulatory cytokines as well as additional cell surface activation markers in relation to serum IgE levels.

METHOD

We selected ten individuals at both the lower and higher end of a spectrum of plasma IgE concentrations from 29 nonatopic individuals and compared the differences in cytokine and activation marker expression in relation to IgE production.

RESULTS

We found that even upon extensive examination of activation markers on T, B, and NK cell subsets, there are no significant differences in the cell populations or surface marker expression between the high IgE and low IgE groups. Messenger RNA expression in peripheral blood mononuclear cells (PBMCs) of the cytokines IL-4 and IL-6 was significantly higher, whereas IL-10 was lower in the high IgE group. In addition upon in vitro polyclonal stimulation of peripheral blood mononuclear cells, individuals of the high IgE group produced lower levels of IL-2, IFN gamma and IL-10 compared to the low IgE donors.

CONCLUSION

Since our results differ from studies using atopic individuals, this study demonstrates the importance of using nonatopic individuals for examining associations between various immune parameters and IgE.

IgE+ cells in the peripheral blood of atopic, nonatopic, and bee venom-hypersensitive individuals exhibit the phenotype of highly differentiated B cells

We have analyzed IgE+ cells in peripheral blood of atopic donors, donors hypersensitive to bee venom, and nonatopic control donors with two- and three-color flow cytometry. Although the percentage of IgE+ cells varied among these groups, the overall phenotypic patterns were similar. Most IgE+ cells do not display typical B-cell markers, such as CD19, CD20, and CD21. A significant proportion of these cells stain for CD38, indicating that they are more differentiated. IgE+ cells express Fc gamma RII and CD45RO, an isoform associated with an advanced level of differentiation. The majority of IgE+ cells do not coexpress other surface immunoglobulin isotypes. In the case of bee venom-hypersensitive donors, we have been able to identify a small population of IgE+ cells with a specificity for phospholipase A2, a major immunogenic component of bee venom. The phospholipase A2+ cells display a phenotype similar to that of the IgE+ cells.

Diesel exhaust particles induce local IgE production in vivo and alter the pattern of IgE messenger RNA isoforms

Diesel exhaust particles (DEP) have been implicated in the increased incidence of allergic airway disorders. We investigated the effects of DEP on localized immunoglobulin production by performing nasal challenges with varying doses of DEP and analyzing the local immune response in nasal lavages obtained before and after. A significant rise in nasal IgE but not IgG, IgA, IgM, or albumin was observed in subjects 4 d after challenge with 0.30 mg DEP, equivalent to exposure on an average Los Angeles day. Direct evidence for DEP-enhanced local production of IgE was that challenge increased the number of IgE-secreting cells in lavage fluid from < 1 in 2,000,000 to > 1 in 100,000 but did not alter the number of IgA-secreting cells. There was a concomitant increase in epsilon mRNA production in the lavage cells. Additionally, DEP altered the relative amounts of five different epsilon mRNAs generated by alternative splicing, mRNAs that code for different IgE proteins. These results show that DEP exposure in vivo causes both quantitative and qualitative changes in local IgE production. The implication is that natural exposure to DEP may result in increased expression of respiratory allergic disease.

A solid phase enzyme linked immunofiltration assay for secretory leucocyte proteinase inhibitor

A solid phase enzyme linked immunosorbent filtration assay (ELIFA) has been developed for secretory leucocyte proteinase inhibitor (SLPI) utilising polyclonal anti-recombinant SLPI (anti-rSLPI) and polyclonal anti-bronchial mucus proteinase inhibitor (anti-BLPI) IgG samples. Millipore HATF nitrocellulose 96-well plates were used as receptacles for the assay and a commercial goat anti-rabbit IgG alkaline phosphatase conjugate was used as a secondary antibody for quantitation of levels of primary antibodies bound to rSLPI in the plate wells. Antigen bound to the HATF plates efficiently and the washing/blocking steps were simplified by vacuum filtration of samples resulting in a rapid and convenient assay system. The ELIFA was also sensitive and a detection limit of 0.1 ng SLPI/well was achieved using either anti-SLPI or anti-BLPI as primary antibodies. This assay was used to demonstrate the production of SLPI at moderate levels (0.5-3 ng/ml media) by human articular chondrocytes grown in monolayer culture.

Detection of autologous antiidiotypic antibody-forming cells by a modified enzyme-linked immunospot (ELISPOT)

We describe here the utilization of a modified enzyme-linked immunospot assay (ELISPOT) in order to detect an autologous antiidiotypic response in mice at the level of single antibody-forming cells (AFC). Severals assays have been routinely used to detect anti-Id producing cells; however, these approaches often produce contrasting data. We present results obtained with the modified ELISPOT, using as a model system the antiidiotypic response in mice after immunization with a vaccine from Streptococcus pneumoniae R36a, expressing the immunodominant epitope phosphorylcholine (PC). The response to PC is mediated by a large fraction of antibodies bearing the public idiotype T15. Mice of different genetics make up were immunized with a single injection of the vaccine. We observed that one mouse strain (D1.LP) out of three was able to mount a significant anti-T15 response during the primary anti-phosphorylcholine response. BALB/c and C57BL/6 mice did not produce significant levels of anti-T15 antibody following a single injection of the antigen. In contrast, BALB/c mice which were repeatedly stimulated showed a specific anti-Id response. Experimental controls were performed using either specific anti-T15 monoclonal antibodies (mAb) or splenocytes from mice immunized with TEPC15 myeloma protein in complete Freund's adjuvant.