Analysis of IgE antibodies from a patient with atopic dermatitis: biased V gene usage and evidence for polyreactive IgE heavy chain complementarity-determining region 3

B cell profiles, antibody repertoire and reactivity reveal dysregulated responses with autoimmune features in melanoma

B cells are known to contribute to the anti-tumor immune response, especially in immunogenic tumors such as melanoma, yet humoral immunity has not been characterized in these cancers to detail. Here we show comprehensive phenotyping in samples of circulating and tumor-resident B cells as well as serum antibodies in melanoma patients. Memory B cells are enriched in tumors compared to blood in paired samples and feature distinct antibody repertoires, linked to specific isotypes. Tumor-associated B cells undergo clonal expansion, class switch recombination, somatic hypermutation and receptor revision. Compared with blood, tumor-associated B cells produce antibodies with proportionally higher levels of unproductive sequences and distinct complementarity determining region 3 properties. The observed features are signs of affinity maturation and polyreactivity and suggest an active and aberrant autoimmune-like reaction in the tumor microenvironment. Consistent with this, tumor-derived antibodies are polyreactive and characterized by autoantigen recognition. Serum antibodies show reactivity to antigens attributed to autoimmune diseases and cancer, and their levels are higher in patients with active disease compared to post-resection state. Our findings thus reveal B cell lineage dysregulation with distinct antibody repertoire and specificity, alongside clonally-expanded tumor-infiltrating B cells with autoimmune-like features, shaping the humoral immune response in melanoma.

Protocol to determine antibody affinity and concentration in complex solutions using microfluidic antibody affinity profiling

Conventional methods of measuring affinity are limited by artificial immobilization, large sample volumes, and homogeneous solutions. This protocol describes microfluidic antibody affinity profiling on complex human samples in solution to obtain a fingerprint reflecting both affinity and active concentration of the target protein. To illustrate the protocol, we analyze the antibody response in SARS-CoV-2 omicron-naïve samples against different SARS-CoV-2 variants of concern. However, the protocol and the technology are amenable to a broad spectrum of biomedical questions. For complete details on the use and execution of this protocol, please refer to Emmenegger et al. (2022),1 Schneider et al. (2022),2 and Fiedler et al. (2022).3.

IgE repertoire and immunological memory: compartmental regulation and antibody function

It is now generally recognized that bone marrow is the survival niche for antigen-specific plasma cells with long-term immunological memory. These cells release antibodies into the circulation, needed to prime effector cells in the secondary immune response. These antibodies participate in the surveillance for antigen and afford immune defence against pathogens and toxins previously encountered in the primary immune response. IgE antibodies function together with their effector cells, mast cells, to exert 'immediate hypersensitivity' in mucosal tissues at the front line of immune defence. The constant supply of IgE antibodies from bone marrow plasma cells allows the rapid 'recall response' by mast cells upon re-exposure to antigen even after periods of antigen absence. The speed and sensitivity of the IgE recall response and potency of the effector cell functions are advantageous in the early detection and elimination of pathogens and toxins at the sites of attack. Local antigen provocation also stimulates de novo synthesis of IgE or its precursors of other isotypes that undergo IgE switching in the mucosa. This process, however, introduces a delay before mast cells can be sensitized and resume activity; this is terminated shortly after the antigen is eliminated. Recent results from adaptive immune receptor repertoire sequencing of immunoglobulin genes suggest that the mucosal IgE+ plasmablasts, which have undergone affinity maturation in the course of their evolution in vivo, are a source of long-lived IgE+ plasma cells in the bone marrow that are already fully functional.

Peripheral IgE Repertoires of Healthy Donors Carry Moderate Mutation Loads and Do Not Overlap With Other Isotypes

IgE-mediated allergic disease represents an increasing health problem. Although numerous studies have investigated IgE sequences in allergic patients, little information is available on the healthy IgE repertoire. IgM, IgG, IgA, and IgE transcripts from peripheral blood B cells of five healthy, non-atopic individuals were amplified by unbiased, template-switching, isotype-specific PCR. Complete VDJ regions were sequenced to near-exhaustion on the PacBio platform. Sequences were analyzed for clonal relationships, degree of somatic hypermutation, IGHV gene usage, evidence of antigenic selection, and N-linked glycosylation motifs. IgE repertoires appeared to be highly oligoclonal with preferential usage of certain IGHV genes compared to the other isotypes. IgE sequences carried more somatic mutations than IgM, yet fewer than IgG and IgA. Many IgE sequences contained N-linked glycosylation motifs. IgE sequences had no clonal relationship with the other isotypes. The IgE repertoire in healthy individuals is derived from relatively few clonal expansions without apparent relations to immune reactions that give rise to IgG or IgA. The mutational burden of normal IgE suggests an origin through direct class-switching from the IgM repertoire with little evidence of antigenic drive, and hence presumably low affinity for specific antigens. These findings are compatible with a primary function of the healthy IgE repertoire to occupy Fcε receptors for competitive protection against mast cell degranulation induced by allergen-specific, high-affinity IgE. This background knowledge may help to elucidate pathogenic mechanisms in allergic disease and to design improved desensitization strategies.

On the Lipophilic Nature of Autoreactive IgE in Chronic Spontaneous Urticaria

Chronic spontaneous urticaria (CSU) is a skin disease related to autoreactive IgE in at least a subgroup of patients. However, the nature of this autoreactive IgE remains poorly characterized. This investigation had three objectives: first, to quantity CSU autoreactive IgE; second, to recognize the patterns of CSU autoreactive IgE compared with healthy control IgE; and third, to investigate the physiochemical nature of CSU autoreactive IgE.

Methods: IgE autoreactivity was assessed in sera from 7 CSU and 7 healthy individuals. Autoantigen recognition patterns were assessed using principal component analysis (PCA) and heatmap visualization. Lipophilicity was assessed using NanoOrange reagent.

Results: First, although total IgE levels did not differ significantly, the autoreactive proportion of IgE of CSU patients was 62% ± 37%, 1000-fold higher than that of healthy controls 0.03% ± 0.008% (P = 0.0006). Second, CSU autoreactive IgE differed from healthy control IgE by recognizing more and different autoantigens (226 vs. 34; P = 0.01). Third, the median (with 10-90% percentiles) serum level of lipophilic IgE was 39% (38-40%) in 232 CSU patients, 1.4-fold higher than the 28% (26-29%) of 173 healthy controls (P < 0.0001). Furthermore, lipophilicity correlated with autoreactivity (r = 0.8; P < 0.0001), connecting these two observed features.

Conclusion: We believe that these novel observations about CSU autoreactive IgE, particularly the finding that it is more lipophilic than that of IgE from healthy individuals, will lead to the development of new diagnostic tests and therapies for autoreactive IgE-mediated diseases.

A role for macromolecular crowding in off-target binding of therapeutic antibodies

The nonspecific binding of certain therapeutic antibodies to tissues or to soluble biomolecules can accelerate their clearance from the circulation and undermine their benefit to patients. This article proposes that tandem amino acid repeat sequences in antibody hypervariable segments, particularly the complementarity determining regions (CDRs), can enhance this off-target binding. This hypothesis is based on two sets of observations. First, in a limited number of cases, antibodies with clusters of amino acid repeats in their CDRs have significantly higher clearance rates in experimental animals than otherwise identical antibodies without the repeats. Second, tandem amino acid repeats are abundant in intracellular hub proteins where they appear to promote the promiscuous binding of these proteins to a wide variety of other molecules. These nonspecific hub protein interactions are highly favored by the intense macromolecular crowding that permeates the cytoplasm. A survey of the variable region sequences of 137 antibodies in various stages of development revealed that 26 have at least one CDR containing a cluster of three closely spaced amino acid repeats. If the overall hypothesis is valid, then it suggests strategies for site-directed mutagenesis to improve pharmacokinetic behavior and for the design of more reliable in vitro binding assays to predict off-target binding in vivo.

Single B-cell deconvolution of peanut-specific antibody responses in allergic patients

BACKGROUND

The frequencies, cellular phenotypes, epitope specificity, and clonal diversity of allergen-specific B cells in patients with food allergy are not fully understood but are of major pathogenic and therapeutic significance.

OBJECTIVE

We sought to characterize peanut allergen-specific B-cell populations and the sequences and binding activities of their antibodies before and during immunotherapy.

METHODS

B cells binding fluorescently labeled Ara h 1 or Ara h 2 were phenotyped and isolated by means of flow cytometric sorting from 18 patients at baseline and 13 patients during therapy. Fifty-seven mAbs derived from allergen-binding single B cells were evaluated by using ELISA, Western blotting, and peptide epitope mapping. Deep sequencing of the B-cell repertoires identified additional members of the allergen-specific B-cell clones.

RESULTS

Median allergen-binding B-cell frequencies were 0.0097% (Ara h 1) or 0.029% (Ara h 2) of B cells in baseline blood from allergic patients and approximately 3-fold higher during immunotherapy. Five of 57 allergen-specific cells belonged to clones containing IgE-expressing members. Almost all allergen-specific antibodies were mutated, and binding to both conformational and linear allergen epitopes was detected. Increasing somatic mutation of IgG4 members of a clone was seen in immunotherapy, whereas IgE mutation levels in the clone did not increase.

CONCLUSION

Most peanut allergen-binding B cells isolated by means of antigen-specific flow sorting express mutated and isotype-switched antibodies. Immunotherapy increases their frequency in the blood, and even narrowly defined allergen epitopes are recognized by numerous distinct B-cell clones in a patient. The results also suggest that oral immunotherapy can stimulate somatic mutation of allergen-specific IgG4.

Influence of seasonal exposure to grass pollen on local and peripheral blood IgE repertoires in patients with allergic rhinitis

Background

Previous studies of immunoglobulin gene sequences in patients with allergic diseases using low-throughput Sanger sequencing have limited the analytic depth for characterization of IgE repertoires.

Objectives

We used a high-throughput, next-generation sequencing approach to characterize immunoglobulin heavy-chain gene (IGH) repertoires in patients with seasonal allergic rhinitis (AR) with the aim of better understanding the underlying disease mechanisms.

Methods

IGH sequences in matched peripheral blood and nasal biopsy specimens from nonallergic healthy control subjects (n = 3) and patients with grass pollen–related AR taken in season (n = 3) or out of season (n = 4) were amplified and pyrosequenced on the 454 GS FLX+ System.

Results

A total of 97,610 IGH (including 8,135 IgE) sequences were analyzed. Use of immunoglobulin heavy-chain variable region gene families 1 (IGHV1) and 5 (IGHV5) was higher in IgE clonotypic repertoires compared with other antibody classes independent of atopic status. IgE repertoires measured inside the grass pollen season were more diverse and more mutated (particularly in the biopsy specimens) and had more evidence of antigen-driven selection compared with those taken outside of the pollen season or from healthy control subjects. Clonal relatedness was observed for IgE between the blood and nasal biopsy specimens. Furthermore in patients with AR, but not healthy control subjects, we found clonal relatedness between IgE and IgG classes.

Conclusion

This is the first report that exploits next-generation sequencing to determine local and peripheral blood IGH repertoires in patients with respiratory allergic disease. We demonstrate that natural pollen exposure was associated with changes in IgE repertoires that were suggestive of ongoing germinal center reactions. Furthermore, these changes were more often apparent in nasal biopsy specimens compared with peripheral blood and in patients with AR compared with healthy control subjects.

Human IgE against the major allergen Bet v 1--defining an epitope with limited cross-reactivity between different PR-10 family proteins

Background

The interaction between IgE and allergen is a key event at the initiation of an allergic response, and its characteristics have substantial effects on the clinical manifestation. Despite this, the molecular details of the interaction between human IgE and the major birch allergen Bet v 1, one of the most potent tree allergens, still remain poorly investigated.

Objective

To isolate Bet v 1-specific human monoclonal IgE and characterize their interaction with the allergen.

Methods

Recombinant human IgE were isolated from a combinatorial antibody fragment library and their interaction with Bet v 1 assessed using various immunological assays. The structure of one such IgE in the single-chain fragment variable format was determined using X-ray crystallography.

Results

We present four novel Bet v 1-specific IgE, for one of which we solve the structure, all with their genetic origin in the IGHV5 germline gene, and demonstrate that they target two non-overlapping epitopes on the surface of Bet v 1, thereby fulfilling the basic criteria for FcεRI cross-linkage. We further define these epitopes and for one epitope pinpoint single amino acid residues important for the interaction with human IgE. This provides a potential explanation, at the molecular level, for the differences in recognition of isoforms of Bet v 1 and other allergens in the PR-10 protein family displayed by IgE targeting this epitope. Finally, we present the first high-resolution structure of a human allergen-specific IgE fragment in the single-chain fragment variable (scFv) format.

Conclusions and Clinical Relevance

We here display the usefulness of allergen-specific human monoclonal IgE as a tool in studies of the crucial molecular interaction taking place at the initiation of an allergic response. Such studies may aid us in development of better diagnostic tools and guide us in the development of new therapeutic compounds.

The human IgE repertoire

IgE is a key mediator in allergic diseases. However, in strong contrast to other antibody isotypes, many details of the composition of the human IgE repertoire are poorly defined. The low levels of human IgE in the circulation and the rarity of IgE-producing B cells are important reasons for this lack of knowledge. In this review, we summarize the current knowledge on these repertoires both in terms of their complexity and activity, i.e. knowledge which despite the difficulties encountered when studying the molecular details of human IgE has been acquired in recent years. We also take a look at likely future developments, for instance through improvements in sequencing technology and methodology that allow the isolation of additional allergen-specific human antibodies mimicking IgE, as this certainly will support our understanding of human IgE in the context of human disease in the years to come.

The longevity of Th2 humoral response induced by proteases natterins requires the participation of long-lasting innate-like B cells and plasma cells in spleen

The generation of long-lived antibody-secreting cells (ASC) and memory B cells are critical events for an effective vaccine and the choice of adjuvant can influence these processes. Various cellular and molecular mechanism involved in the protease action that determine Th2 responses have been identified. However, direct or indirect actions in the regulation of the induction, survival and longevity of ASC in differential compartments remain largely unknown. We investigated whether the proteolytic activity of proteins are determinant for the modulation of the memory immune response in mice, promoting the differentiation of memory B cells to terminally differentiated end stage cells. Here, we show that the proteolytic activity of Natterins, from the venom of Thalassophryne nattereri Brazilian fish, besides inducing a Th2 response with plasmatic titers of high-affinity antigen-specific IgE over extended periods is sufficient for the generation of signals that contribute to the formation of a survival niche in the spleen, essential for the longevity of the main subtype of ASC with B220^neg phenotype.

Determination of allergen specificity by heavy chains in grass pollen allergen-specific IgE antibodies

BACKGROUND

Affinity and clonality of allergen-specific IgE antibodies are important determinants for the magnitude of IgE-mediated allergic inflammation.

OBJECTIVE

We sought to analyze the contribution of heavy and light chains of human allergen-specific IgE antibodies for allergen specificity and to test whether promiscuous pairing of heavy and light chains with different allergen specificity allows binding and might affect affinity.

METHODS

Ten IgE Fabs specific for 3 non-cross-reactive major timothy grass pollen allergens (Phl p 1, Phl p 2, and Phl p 5) obtained by means of combinatorial cloning from patients with grass pollen allergy were used to construct stable recombinant single chain variable fragments (ScFvs) representing the original Fabs and shuffled ScFvs in which heavy chains were recombined with light chains from IgE Fabs with specificity for other allergens by using the pCANTAB 5 E expression system. Possible ancestor genes for the heavy chain and light chain variable region-encoding genes were determined by using sequence comparison with the ImMunoGeneTics database, and their chromosomal locations were determined. Recombinant ScFvs were tested for allergen specificity and epitope recognition by means of direct and sandwich ELISA, and affinity by using surface plasmon resonance experiments.

RESULTS

The shuffling experiments demonstrate that promiscuous pairing of heavy and light chains is possible and maintains allergen specificity, which is mainly determined by the heavy chains. ScFvs consisting of different heavy and light chains exhibited different affinities and even epitope specificity for the corresponding allergen.

CONCLUSION

Our results indicate that allergen specificity of allergen-specific IgE is mainly determined by the heavy chains. Different heavy and light chain pairings in allergen-specific IgE antibodies affect affinity and epitope specificity and thus might influence clinical reactivity to allergens.

IgE sequences in individuals living in an area of endemic parasitism show little mutational evidence of antigen selection

Patterns of somatic mutation in IgE genes from allergic individuals have been a focus of study for many years, but IgE sequences have never been reported from parasitized individuals. To study the role of antigen selection in the evolution of the anti-parasite response, we therefore generated 118 IgE sequences from donors living in Papua New Guinea (PNG), an area of endemic parasitism. For comparison, we also generated IgG1, IgG2, IgG3 and IgG4 sequences from these donors, as well as IgG1 sequences from Australian donors. IgE sequences had, on average, 23.0 mutations. PNG IgG sequences had average mutation levels that varied from 17.7 (IgG3) to 27.1 (IgG4). Mean mutation levels correlated significantly with the position of their genes in the constant region gene locus (IgG3 < IgG1 < IgG2 < IgG4). Interestingly, given the heavy, life-long antigen burden experienced by PNG villagers, average mutation levels in IgG sequences were little different to that seen in Australian IgG1 sequences (19.2). Patterns of mutation provide clear evidence of antigen selection in many IgG sequences. The percentage of IgG sequences that showed significant accumulations of replacement mutations in the complementarity determining regions ranged from 22% of IgG3 sequences to 39% of IgG2 sequences. By contrast, only 12% of IgE sequences had such evidence of antigen selection, and this was significantly less than in PNG IgG1, IgG2 and IgG4 subclass sequences (P < 0.01). The anti-parasite IgE response therefore has the reduced evidence of antigen selection that has previously been reported in studies of IgE sequences from allergic individuals.

IgE transcripts in the circulation of allergic children reflect a classical antigen-driven B cell response and not a superantigen-like activation

Allergic asthma is the most frequent chronic disorder in childhood. Although IgE is a central effector molecule in allergic diseases, the nature of the IgE response is still under debate. The objective of our study was to clarify whether the IgE repertoire in the circulation of allergic children represents a classical Ag-driven and oligoclonal B cell response, a superantigen-like activation of a subset of B cells, or a polyclonal B-1 cell expansion. Using a highly sensitive RT-PCR method, we amplified, cloned, and sequenced IgE H chain transcripts from 13 children with allergic asthma. We gained 1366 functional IgE sequences, which currently represent the most extensive collection of human IgE transcripts. Compared to IgM transcripts from the same children, the somatic mutation rate was significantly enhanced in IgE transcripts (21 per thousand versus 72 per thousand; p < 0.001), which renders a polyclonal B-1 response unlikely. Moreover, IgE sequences displayed significantly enhanced Ag selection and hence were indicative of a classical Ag-driven immune response with affinity maturation (p < 0.001). In contrast to several recent studies, the usage pattern of variable gene segment of the H Ig chain in IgE transcripts followed the germline complexity, arguing against a superantigen-like interaction. We conclude that IgE transcripts in the circulation of children with allergic asthma reflect a classical adaptive B-2 cell response. This study provides reference data for a better characterization of the IgE response under immunomodulating therapies, such as anti-IgE therapy or allergen-specific immunotherapy.

Tracing antigen signatures in the human IgE repertoire

Allergen recognition by IgE antibodies is a key event in allergic inflammation.

In this study, the IgE IGHV repertoires of individuals with allergy to the major birch pollen allergen, Bet v 1, were analyzed over a four years period of allergen exposure by RT-PCR and sequencing of cDNA.

Approximately half of the IgE transcripts represented non-redundant sequences, which belonged to seventeen different IGHV genes. Most variable regions contained somatic mutations but also non-mutated sequences were identified. There was no evidence for relevant increases of somatic mutations over time of allergen exposure. Highly similar IgE variable regions were found after four years of allergen exposure in the same and in genetically non-related individuals.

Our results indicate that allergens select and shape a limited number of similar IgE variable regions in the human IgE repertoire.

Composition of the immunoglobulin classic antigen-binding site regulates allergic airway inflammation in a murine model of experimental asthma

BACKGROUND

When bound to mast cell FcepsilonRI, IgE serves as antigen receptor for allergic reactions, permitting specific identification of the allergen. Although the core of the classic antigen-binding site is heavy chain complementarity determining region 3 (CDR-H3), recent studies suggest that allergens might also bind IgE in a superantigen-like fashion outside the classic antigen-binding site.

OBJECTIVE

We sought to evaluate the contribution of the classic CDR-H3-centric antigen-binding site to the development of an allergic phenotype.

METHODS

Using a murine model of experimental asthma, we characterized a gene-targeted mouse strain expressing an altered range of CDR-H3s (DeltaD-iD mice) in response to the hydrophobic allergen ovalbumin (OVA). Mutant and wild-type (wt) mice were sensitized intraperitoneally with OVA; non-sensitized mice served as controls.

RESULTS

We found the composition of the classic CDR-H3-centric antigen-binding site to be critical for the development of characteristic aspects of allergic asthma. (i) Compared with wt animals, DeltaD-iD mice showed a significantly less pronounced OVA-induced rise in allergen-specific IgE levels and hence in total serum IgE levels. (ii) In addition, DeltaD-iD mice demonstrated a significant reduction in eosinophilic airway inflammation, as well as in interleukin-4 (IL-4), IL-5 and IL-13 levels in BAL fluids.

CONCLUSION

Allergic sensitization and airway inflammation depend on the composition of the predominant CDR-H3 repertoire, suggesting that the classic CDR-H3-centric antigen-binding site plays a crucial role in creating the immunological interface between allergen and IgE. Our results further emphasize a central role of IgE, not only in mediating but also in regulating the allergic immune response.

Delineating the specificity of an IgE-encoding transcriptome

BACKGROUND

Although much is known about the reactivity of polyclonal populations of antibodies targeting the wide array of allergens produced by timothy (Phleum pratense) and other grass species, little is known about the finer details at the level of individual antibody specificities.

OBJECTIVE

We sought to investigate the IgE repertoire as it occurs in a patient with grass pollen allergy.

METHODS

For this purpose, a human IgE library was used, constructed from peripheral blood B cells of an individual with timothy allergy. The library was screened by using phage display against a panel of 6 timothy allergens (Phl p 1, Phl p 2, Phl p 4, Phl p 5, Phl p 6, and Phl p 11).

RESULTS

Highly diverse antibody fragments with respect to gene usage were identified. The binders were specific for their respective target antigen, except for clones selected on Phl p 6 that also recognized Phl p 5, most likely reflecting the high sequence homology between these allergens. Interestingly, by using this approach, we were able to determine the specificity of more than 25% of all IgE-producing transcripts in this individual with allergy.

CONCLUSION

The human IgE repertoire is produced by a limited number of highly related B-cell clones and as such is restricted in its recognition of a limited number of antigens.

CLINICAL IMPLICATIONS

Human allergen-specific antibodies can, by defining the specificity of IgE responses, aid in the development of allergy vaccines or even by themselves be used in passive immunotherapy.

The IgE repertoire in PBMCs of atopic patients is characterized by individual rearrangements without variable region of the heavy immunoglobulin chain bias

BACKGROUND

Patients with atopic diseases are characterized by high levels of specific IgE production. However, little is known about the composition of their B-cell repertoires.

OBJECTIVES

We sought to analyze the complete PBMC-derived IgE repertoire and to compare clonal expansions between different patients.

METHODS

We have analyzed the IgE-bearing B-cell receptor repertoire in highly atopic patients (>1000 IU/mL) using quantitative RT-PCR, complementarity determining region 3 spectratyping, and sequence analysis. Three representative patients were additionally followed during anti-IgE therapy.

RESULTS

Atopic patients exhibited 100 to 1000 times more IgE-specific transcripts than control individuals. These patients used a variable region of the heavy immunoglobulin chain (VH) epsilon repertoire highly similar to their IgM and IgG repertoires, with preference of VH3b, VH4, VH3a, and VH1 segments. Each patient harbored individual clonal expansions, most probably as correlation of allergen-specific IgE production. Common expansions within the complementary determining region 3 shared by several individuals with similar sensitization patterns were found in spectratyping analysis. However, these antigen-driven expansions showed differences on the sequence level. In omalizumab-treated patients the clinical improvement was paralleled by a clear increase in the ratio of IgG/IgE transcripts.

CONCLUSION

The IgE repertoire in atopic patients follows the VH use patterns seen for other immunoglobulins and seems to preferentially recruit individual rearrangements rather than public expansions.

CLINICAL IMPLICATIONS

The detailed analysis of the IgE B-cell repertoire is highly suitable to follow changes in IgE uses during different therapy modalities.

The human IgE-encoding transcriptome to assess antibody repertoires and repertoire evolution

Upon encounter with antigen, the B lymphocyte population responds by producing a diverse set of antigen-specific antibodies of various isotypes. The vast size of the responding populations makes it very difficult to study clonal evolution and repertoire composition occurring during these processes in humans. Here, we have explored an approach utilizing the H-EPSILON-encoding transcriptome to investigate aspects of repertoire diversity during the season of antigen exposure. We show through sequencing of randomly picked transcripts that the sizes of patients' repertoires are relatively small. This specific aspect of the transcriptome allows us to construct evolutionary trees pinpointing features of somatic hypermutation as it occurs in humans. Despite the small size of the repertoires, they are highly diverse with respect to VDJ gene usage, suggesting that the H-EPSILON-encoding transcriptome is a faithful mimic of other class-switched isotypes. Importantly, it is possible to use antibody library and selection technologies to define the specificity of clonotypes identified by random sequencing. The small size of the H-EPSILON-encoding transcriptome of peripheral blood B cells, the simple identification of clonally related sets of genes in this population, and the power of library and selection technologies ensure that this approach will allow us to investigate antibody evolution in human B lymphocytes of known specificity. As H-EPSILON repertoires show many of the hallmarks of repertoires encoding other isotypes, we suggest that studies of this type will have an impact on our understanding of human antibody evolution even beyond that occurring in the IgE-producing B cell population.

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

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

VH gene usage in immunoglobulin E responses of seasonal rhinitis patients allergic to grass pollen is oligoclonal and antigen driven

BACKGROUND

IgE is the pivotal-specific effector molecule of allergic reactions yet it remains unclear whether the elevated production of IgE in atopic individuals is due to superantigen activation of B cell populations, increased antibody class switching to IgE or oligoclonal allergen-driven IgE responses.

OBJECTIVES

To increase our understanding of the mechanisms driving IgE responses in allergic disease we examined immunoglobulin variable regions of IgE heavy chain transcripts from three patients with seasonal rhinitis due to grass pollen allergy.

METHODS

Variable domain of heavy chain-epsilon constant domain 1 cDNAs were amplified from peripheral blood using a two-step semi-nested PCR, cloned and sequenced.

RESULTS

The VH gene family usage in subject A was broadly based, but there were two clusters of sequences using genes VH 3-9 and 3-11 with unusually low levels of somatic mutations, 0-3%. Subject B repeatedly used VH 1-69 and subject C repeatedly used VH 1-02, 1-46 and 5a genes. Most clones were highly mutated being only 86-95% homologous to their germline VH gene counterparts and somatic mutations were more abundant at the complementarity determining rather than framework regions. Multiple sequence alignment revealed both repeated use of particular VH genes as well as clonal relatedness among clusters of IgE transcripts.

CONCLUSION

In contrast to previous studies we observed no preferred VH gene common to IgE transcripts of the three subjects allergic to grass pollen. Moreover, most of the VH gene characteristics of the IgE transcripts were consistent with oligoclonal antigen-driven IgE responses.

Dermatite atopique : quels sont les critères diagnostiques utilisés dans les articles scientifiques ?

INTRODUCTION

Diagnosis of atopic dermatitis currently relies on diagnostic criteria scales developed by Hanifin and Rafka in 1980 and by the "United Kingdom Working party" in 1994. Some authors have proposed: "AEDS" [sM1] and "Atopiform Dermatitis", which has led to the distinction between different sub-populations and the exclusion of certain diseases from the diagnosis of atopic dermatitis. The aim of our study was to collect the criteria retained in the scientific medical literature during the year 2002 for the definition of atopic dermatitis and to try to understand not only the interest but also the questions that the various definitions lead to.

METHOD

A PubMed research was launched with the key word "atopic dermatitis" from January to September of 2002. All the scientific articles either in French or in English were studied.

RESULTS

Hanifin and Rafka's criteria were selected in 44 p. 100 of the scientific articles, and the "United Kingdom Working Party" criteria in 12 p. 100. Personal definitions were used in 21 p. 100 of the articles; these were based on the level of total and specific IgE or on personal clinical criteria. For twenty-three p. 100 of the authors, the definition of atopic dermatitis was not specified.

DISCUSSION

There was not just one definition of atopic dermatitis. This may affect the interpretation of diagnostic or therapeutic papers concerning the disease, because there has been no proof that these definitions cover the same population of patients.

Immunoglobulin gene rearrangement, repertoire diversity, and the allergic response

The immunoglobulin repertoire arises as a consequence of combinatorial diversity, junctional diversity, and the process of somatic point mutation. Each of these processes involves biases that limit and shape the available immunoglobulin repertoire. The expressed repertoire is further shaped by selection, to the extent that biased gene usage can become apparent in many disease states. The study of rearranged immunoglobulin genes therefore may not only provide insights into the molecular processes involved in the generation of antibody diversity but also inform us of pathogenic processes and perhaps identify particular lymphocyte clones as therapeutic targets. Partly as a consequence of the low numbers of circulating IgE-committed B-cells, studies of rearranged IgE genes in allergic individuals have commenced relatively recently. In this review, recent advances in our understanding of the processes of immunoglobulin gene rearrangement and somatic point mutation are described, and biases inherent to these processes are discussed. The evidence that some diseases may be associated with particular gene rearrangements is then considered, with a particular focus on allergic disease. Reviewed data suggest that an important contribution to the IgE response may come from cells that use relatively rare heavy chain V (V(H)) segment genes, which display little somatic point mutation. Some IgE antibodies also seem to display polyreactive binding. In other contexts, these 3 characteristics have been associated with antibodies of the B-1 B-cell subset, and the possibility that B-1 B-cells contribute to the allergic response is therefore considered.