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

An integrated framework using high-dimensional mass cytometry and fluorescent flow cytometry identifies discrete B cell subsets in patients with red meat allergy

BACKGROUND

B cells play a critical role in the development and maintenance of food allergy by producing allergen-specific IgE. Despite the importance of B cells in IgE-mediated food allergy, the identity of sIgE-producing human B cells and how IgE is regulated are poorly understood.

OBJECTIVE

To identify the immunophenotypes of circulating B cells associated with the production of galactose-alpha-1,3-galactose-specific IgE production in patients with red meat allergy.

METHODS

B cells in PBMC samples obtained from 19 adults with physician-diagnosed red meat allergy and 20 non-meat allergic healthy controls were assessed by mass cytometry along with a bioinformatics analysis pipeline to identify discrete B cell phenotypes that associated with serum sIgE. Fluorescent flow cytometry was then applied to sort purify discrete B cell subsets, and B cells were functionally evaluated on an individual cell level for the production of sIgE by ELISPOT.

RESULTS

Discrete B cell phenotypes abundant in meat allergic subjects compared to non-meat allergic controls were found in peripheral blood that do not share typical characteristics of classical isotype-switched memory B cells that express high levels of CD27. These B cell subsets shared higher IgD and lower IgM expression levels coupled with CXCR4, CCR6 and CD25 expression. In vitro polyclonal stimulation of purified B cell subsets from meat allergic subjects demonstrated that these subsets were enriched for cells induced to secrete sIgE.

CONCLUSIONS AND CLINICAL RELEVANCE

Circulating B cells display increased abundance of discrete B cell subsets in meat allergic subjects. This observation, coupled with the capacity of individual B cell subsets to produce sIgE following activation, implicates these novel B cell phenotypes in promoting IgE in meat allergy.

IgE+ B cells are scarce, but allergen-specific B cells with a memory phenotype circulate in patients with allergic rhinitis

BACKGROUND

Despite the critical role of immunoglobulin E (IgE) in allergy, circulating IgE+ B cells are scarce. Here, we describe in patients with allergic rhinitis B cells with a memory phenotype responding to a prototypic aeroallergen.

METHODS

Fifteen allergic rhinitis patients with grass pollen allergy and 13 control subjects were examined. Blood mononuclear cells stained with carboxyfluorescein diacetate succinimidyl ester (CFSE) were cultured with Bahia grass pollen. Proliferation and phenotype were assessed by multicolour flow cytometry.

RESULTS

In blood of allergic rhinitis patients with high serum IgE to grass pollen, most IgE(hi) cells were CD123+ HLA-DR(-) basophils, with IgE for the major pollen allergen (Pas n 1). Both B and T cells from pollen-allergic donors showed higher proliferation to grass pollen than nonallergic donors (P = 0.002, and 0.010, respectively), whereas responses to vaccine antigens and mitogen did not differ between groups. Allergen-driven B cells that divided rapidly (CD19(mid) CD3(-) CFSE(lo) ) showed higher CD27 (P = 0.008) and lower CD19 (P = 0.004) and CD20 (P = 0.004) expression than B cells that were slow to respond to allergen (CD19(hi) CD3(-) CFSE(mid) ). Moreover, rapidly dividing allergen-driven B cells (CD19(mid) CFSE(lo) CD27(hi) ) showed higher expression of the plasmablast marker CD38 compared with B cells (CD19(hi) CFSE(mid) CD27(lo) ) that were slow to divide.

CONCLUSION

Patients with pollen allergy but not control donors have a population of circulating allergen-specific B cells with the phenotype and functional properties of adaptive memory B-cell responses. These cells could provide precursors for allergen-specific IgE production upon allergen re-exposure.

Alterations on peripheral blood B cell subsets induced by allergic rhinitis

OBJECTIVES AND DESIGN

Here we evaluated whether allergic rhinitis to Dermatophagoides pteronyssinus induces alterations on circulating B cell subsets.

MATERIALS AND METHODS

Circulating B cell subsets and isotype expression on antigen-experienced B cells from allergic patients under conventional pharmacological treatment (NO-SIT, n = 15) and under subcutaneous immunotherapy (SCIT, n = 33), and non-allergic subjects (NC, n = 25) were analyzed by flow cytometry.

RESULTS

In allergic patients, we found a significant decrease in IgM(+) and IgG(+) memory B cells and an increase in IgA(+) memory B cells. Additionally, the numbers of circulating IgA(+) plasmablasts in allergic patients were also increased, while those cells expressing IgM were reduced.

CONCLUSIONS

Allergic patients have a disturbed B cell subsets distribution which seems to underlie rhinitis pathogenesis and remain unchanged after SCIT.

The production and regulation of IgE by the immune system

IgE not only provides protective immunity against helminth parasites but can also mediate the type I hypersensitivity reactions that contribute to the pathogenesis of allergic diseases such as asthma, allergic rhinitis and atopic dermatitis. Despite the importance of IgE in immune biology and allergic pathogenesis, the cells and the pathways that produce and regulate IgE are poorly understood. In this Review, we summarize recent advances in our understanding of the production and the regulation of IgE in vivo, as revealed by studies in mice, and we discuss how these findings compare to what is known about human IgE biology.

The who, where, and when of IgE in allergic airway disease

Allergic asthma and allergic rhinitis/conjunctivitis are characterized by a T(H)2-dominated immune response associated with increased serum IgE levels in response to inhaled allergens. Because IgE is a key player in the induction and maintenance of allergic inflammation, it represents a prime target for therapeutic intervention. However, our understanding of IgE biology remains fragmentary. This article puts together our current knowledge on IgE in allergic airway diseases with a special focus on the identity of IgE-secreting cells ("who"), their location ("where"), and the circumstances in which they are induced ("when"). We further consider the therapeutic implications of the insights gained.

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

To better understand V gene usage, specificity, and clonal origins of IgE Abs in allergic reactions, we have constructed a combinatorial Ab library from the mRNA of an adult patient with atopic dermatitis. Sequence analysis of random clones revealed that 33% of clones used the IGHV6-1 H chain V gene segment, the only member of the V(H)6 gene family. IGHV6-1 is rarely used in the expressed adult repertoire; however, it is associated with fetal derived Abs. Features of the V(H)6 rearrangements included short complementarity-determining region 3, frequent use of IGHD7-27 D gene, and little nucleotide addition at the D-J junction. There was also a low level of mutation compared with V(H)1, V(H)3, and V(H)4 rearrangements. The library was expressed as phage-Fab fusions, and specific phage selected by panning on the egg allergen ovomucoid. Upon expression as soluble IgE Fabs, 12 clones demonstrated binding to ovomucoid, skim milk, and BSA by ELISA. Nucleotide sequencing demonstrated that the IGHV6-1 V gene segment encoded each of the 12 multiply reactive IgE Fabs. A cyclic peptide was designed from the complementarity-determining region 3 of several of these clones. The cyclic peptide bound both self and nonself Ags, including ovomucoid, human IgG, tetanus toxoid, and human and bovine von Willebrand factor. These results suggest that some IgE Abs may bind more than one Ag, which would have important implications for understanding the multiple sensitivities seen in conditions such as atopic dermatitis.

The frequency of phospholipase A2 binding of basophilic granulocytes does not decrease during bee-venom-specific immunotherapy

BACKGROUND

The major allergenic component of bee venom is phospholipase A2 (PLA2).

METHODS

In this study, PLA2 was used to analyze and enrich PLA2-binding cells from peripheral blood by high gradient magnetic cell sorting.

RESULTS

In normal donors, the frequency of allergen (PLA2)-binding cells among peripheral blood mononuclear cells (PBMC) as determined by flow cytometry is below 0.1%, whereas in bee-venom-allergic patients, PLA2-binding cells are readily detectable at frequencies of up to 2.3%. In severely bee-venom-allergic patients, many basophilic granulocytes are present, as defined by anti-CD9, CD25, and CD38 mAb, comprising up to 95% of the PLA2-binding cells. From blood of allergic and normal donors, about equal absolute numbers of allergen-binding CD19/21-positive B cells can be enriched. Severe anaphylactic reactions (Mueller grade IV) and failure of or adverse reactions during immunotherapy are associated with high numbers of circulating allergen-binding basophils. Interestingly, in the patients studied, the number of PLA2-binding basophilic granulocytes did not markedly change during rush immunotherapy and up to 6 months of maintenance immunotherapy.

CONCLUSIONS

The specific and reproducible enrichment of PLA2-binding cells provides a new tool for the analysis and monitoring of effector cells in bee-venom-allergic patients with immediate-type hypersensitivity.

Blood group antibodies are made by CD5+ and by CD5- B cells

The B1 subset of B lymphocytes is associated with the production of low-affinity, polyspecific antibodies. B1 cells are generally recognized by their expression of CD5, and comprise the majority of neonatal B cells. The neonate responds to a restricted range of antigens, and generally makes low-affinity IgM antibody. Published data suggest that antibodies against the blood group antigens A and B are found occasionally in cord blood, and develop rapidly in infants as a result of cross-reactivity with bacterial carbohydrate antigens. This suggests that CD5+ B1 cells may be specialized to make antibodies against such carbohydrate antigens. In this study we evaluated the appearance of antibodies against the blood group (ABO) antigens in human infants, using reagents which specifically distinguish between IgM (made by the infant) and IgG (mainly of maternal origin) and immunofluorescence to detect low levels of antibody. Having established that antibody is always detectable by 8 months of age, and frequently much earlier, we developed a plaque assay to examine the phenotype of cells making antibody against blood group antigens. At 8 months of age, CD5+ and CD5- cells were both capable of making anti-blood group antibody.

Distribution of plasma cell markers and intracellular IgE in cell line U266

The IgE-producing plasma cell line U266 was used to study intracellular IgE and the distribution of the plasma cell markers CD38 and PCA-1. We found two separate clusters of U266 based on the differences in their light scatter properties in the flow cytometer. One cluster displayed high scatter signals (high SS), whereas the other showed low scatter signals (low SS). Most (75%) of the cells in the low SS cluster were positive for intracellular IgE. In contrast, high SS cells had a higher expression of surface IgE and a considerably lower proportion of these cells expressed intracellular IgE. Different patterns of expression of the plasma cell antigens CD38 and PCA-1 were observed. While the low SS cluster displayed a high (76%) expression of PCA-1 and a low (5%) CD38 expression, the high SS cluster expressed 21 and 42%, respectively. About 2/3 of the cells in the low SS cluster appeared to be in the G1 phase of the cell cycle while 1/3 were in the S/G2 phase. In the high SS cluster the opposite distribution (2/3 in S/G2) was observed. Taken together our results indicate an association between cell cycle stages, expression of intracellular IgE and plasma cell markers.

Isolation and characterization of allergen-binding cells from normal and allergic donors

BACKGROUND

Flow cytometry of the immune system so far has been limited to the analysis of subpopulations according to lineage markers. The cells involved in a particular immune response could not be assayed due to their low frequency. Here we show the potential of antigen-specific high gradient magnetic cell sorting to enrich cells for visualisation in multiparameter cytometry, functional studies and immortalization.

OBJECTIVES

The aim of this study was the development of an efficient technology for staining and isolation of antigen-binding cells from human peripheral blood. In particular, allergen-specific cells from normal and allergic donors should be analysed and compared to develop a cellular diagnosis of allergy.

STUDY DESIGN

The rare antigen-specific cells were sorted by high-gradient magnetic cell sorting with MACS. Haptenized phospholipase A2 (PLA2), the major allergen of bee venom, or haptenized ParoI, the major allergenic component of Parietaria officinalis, were used as antigens. The cells from normal and allergic donors, binding to the allergen were characterized phenotypically by immuno-fluorescence. Allergen-specific B-cells were immortalized by EBV transformation.

RESULTS AND CONCLUSION

Allergen-specific cells can be enriched from blood of both allergic and normal donors to purities of up to 75%, by high gradient magnetic cell sorting. The specificity of labelling with allergen was confirmed by establishing allergen-specific EBV-transformed B-cell lines from the sorted cells. Clear differences exist in the cellular composition of allergen-binding cells from normal compared to allergic donors. In normal donors the allergen-binding cells are B-cells expressing CD19 and CD21. In allergic donors, in addition to allergen-binding B-cells, occurring in about equal absolute numbers as in normal donors, basophilic granulocytes are labeled by allergen. These cells express CD38, CD9 and CD25 on their surface, and stain for IgE.