Basophils as Key Regulators of Allergic Inflammation and Th2-type Immunity

Effects of increasing sensitizing doses of ovalbumin on airway hyperresponsiveness in asthmatic mice

BACKGROUND

The dosage of ovalbumin (OVA) during the sensitization stage is considered a crucial factor in the development of airway hyperresponsiveness (AHR). However, the inconsistent dosages of sensitizing OVA used in current studies and the lack of research on their impact on AHR are notable limitations.

METHODS

We examined the impact of increasing sensitizing doses of OVA in a murine asthma model, which entailed initial sensitization with OVA followed by repeated exposure to OVA aerosols. BALB/c mice were primed with doses of OVA (0, 10, 20, 50, and 100 μg) plus 1 mg Alum on Days 0 and 7, and were challenged with OVA aerosols (10 mg/mL for 30 min) between Days 14 and 17. Antigen-induced AHR to methacholine (MCh), as well as histological changes, eosinophilic infiltration, and epithelial injury were assessed.

RESULTS

The result indicated that there are striking OVA dose-related differences in antigen-induced AHR to MCh. The most intense antigen-induced AHR to MCh was observed with sensitization at 50 μg, while weaker responses were seen at 10, 20, and 100 μg. Meanwhile, there was a significant increase in eosinophil count with sensitization at 50 μg. The changes of AHR were correlated with total cells count, lymphocytes count, eosinophils count, and basophils count in bronchoalveolar lavage fluid; however, it did not correlate with histological changes such as cellular infiltration into bronchovascular bundles and goblet cell hyperplasia of the bronchial epithelium.

CONCLUSION

Overall, this study demonstrated that sensitization with 50 μg of OVA resulted in the most significant AHR compared to other dosages. These findings may offer valuable insights for future research on mouse asthma modeling protocols.

Allergic and eosinophilic asthma in the era of biomarkers and biologics: similarities, differences and misconceptions

OBJECTIVE

Severe asthma is associated with substantial personal and economic burden; maintaining disease control is the key management goal. Increased understanding of asthma heterogeneity and development of type 2 (T2)-targeting biologics has substantially advanced disease management and outcomes; however, despite both being driven by T2 inflammation, allergic and eosinophilic asthma have different treatment recommendations. We sought to better understand the similarities and differences between allergic and eosinophilic asthma and highlight where misconceptions may arise.

DATA SOURCES

Published articles, pivotal trials, post hoc analyses, and asthma clinical guidelines sourced from PubMed.

STUDY SELECTIONS

Sources reporting allergic and eosinophilic asthma classifications, disease mechanisms, and biomarkers associated with treatment response.

RESULTS

This review highlights that severe allergic and eosinophilic asthma are both driven by T2 inflammation with eosinophils playing a cardinal role. Despite this overlap, treatment recommendations differ based on asthma classification. T2 cytokine gene expression is a reasonably well-established research tool, but not a well-established biomarker in clinical practice, unlike blood eosinophil counts, fractional exhaled nitric oxide, and immunoglobulin E; the clinical relevance of immunoglobulin E as a predictive biomarker remains unclear.

CONCLUSION

Asthma classifications that can be easily characterized at patient level to ensure accurate diagnosis, predict disease trajectory, and treatment response are required. The current dichotomy of allergic and eosinophilic asthma classifications is likely too simplistic, given the similar eosinophil-mediated disease pathophysiology in both classifications. Our results provide future directions to guide clinically meaningful interpretation of asthma endophenotypes, which may improve understanding of severe asthma characterization and aid future advances in defining responders more precisely with personalized medicine approaches.

Mass Cytometry Phenotyping of Human Granulocytes Reveals Novel Basophil Functional Heterogeneity

Basophils, the rarest granulocyte, play critical roles in parasite- and allergen-induced inflammation. We applied mass cytometry (CyTOF) to simultaneously asses 44 proteins to phenotype and functionally characterize neutrophils, eosinophils, and basophils from 19 healthy donors. There was minimal heterogeneity seen in eosinophils and neutrophils, but data-driven analyses revealed four unique subpopulations within phenotypically basophilic granulocytes (PBG; CD45⁺HLA-DR⁻CD123⁺). Through CyTOF and fluorescence-activated cell sorting (FACS), we classified these four PBG subpopulations as (I) CD16^lowFcεRI^highCD244^high (88.5 ± 1.2%), (II) CD16^highFcεRI^highCD244^high (9.1 ± 0.4%), (III) CD16^lowFcεRI^lowCD244^low (2.3 ± 1.3), and (IV) CD16^highFcεRI^lowCD244^low (0.4 ± 0.1%). Prospective isolation confirmed basophilic-morphology of PBG I–III, but neutrophilic-morphology of PBG IV. Functional interrogation via IgE-crosslinking or IL-3 stimulation demonstrated that PBG I–II had significant increases in CD203c expression, whereas PBG III–IV remained unchanged compared with media-alone conditions. Thus, PBG III–IV could serve roles in non-IgE-mediated immunity. Our findings offer new perspectives in human basophil heterogeneity and the varying functional potential of these new subsets in health and disease.

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Unsupervised clustering revealed 4 basophil populations, driven by CD16, CD244, and FcεRI

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The rarest basophil subpopulation IV was morphologically neutrophils

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Anti-IgE and IL-3 stimulation did not induce functional responses in III and IV

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Basophil subpopulation heterogeneity was observed in healthy and CML samples

Effect of Oreodoxa oleracea Jacq. pollen protein allergen in albino mice

INTRODUCTION

Pollen trigger allergenic reactions in hypersensitive individuals due to the presence of protein in their sporoderm.

AIM

Pollen protein produced by Oreodoxa oleracea was subjected to allergenicity test in mice in order to determine its allergenic potential.

MATERIAL AND METHODS

Pollen protein was extracted using 0.02 M phosphate buffered saline and used to inoculate mice by two subcutaneous and one intranasal injections weekly for 4 weeks. Blood samples were obtained by retro-orbital bleedings, sera obtained were used in detecting immunoglobulin E (IgE) by immunoperoxidase assay. Values of immune cell and IgE elicited in mice were analysed using SPSS statistical package version 20.

RESULTS

Oreodoxa oleracea yielded 208 µg/ml pollen protein allergen. Inoculation of pollen protein in mice produced dermatophytic allergic reactions which physically presented as swelling, rashes and hair loss. Pollen protein skewed basophil production and infiltration of lymphocytes by 1-62% and 58-99% respectively in relation to controls. Histopathology analysis showed inflammation within the lung parenchyma.

CONCLUSIONS

The present study is the first study to evaluate the allergenic potential of Oreodoxa oleracea in mice. The findings revealed that Oreodoxa oleracea which is profoundly planted in pubic areas for aesthetic purposes possess allergenic effect.

The role of basophils as innate immune regulatory cells in allergy and immunotherapy

Basophils are circulating cells that are associated quite exclusively with allergy response and hypersensitivity reactions but their role in the immune network might be much more intriguing and complex than previously expected. The feasibility of testing their biology in vitro for allergy research and diagnosis, due fundamentally to their quite easy availability in the peripheral blood, made them the major source for assessing allergy in the laboratory assay, when yet many further cells such as mast cells and eosinophils are much more involved as effector cells in allergy than circulating basophils. Interestingly, basophil numbers change rarely in peripheral blood during an atopic response, while we might yet observe an increase in eosinophils and modification in the biology of mast cells in the tissue during an hypersensitivity response. Furthermore, the fact that basophils are very scanty in numbers suggests that they should mainly serve as regulatory cells in immunity, rather than effector leukocytes, as still believed by the majority of physicians. In this review we will try to describe and elucidate the possible role of these cells, known as "innate IL4-producing cells" in the immune regulation of allergy and their function in allergen immunotherapy.

Adding injury to infection: The relationship between injury status and genetic diversity of Theileria infecting plains zebra, Equus quagga

Asymptomatic tick-borne infections are a common feature in wild herbivores. In human-dominated habitats, snare injuries to wild herbivores are common and are likely to co-occur with enzootic infections. The influence of injury on pattern, course and outcome of enzootic infection in wild herbivores is unknown. We identified Theileria species infecting zebra and assessed the relationship between host injury-status and parasitaemia, parasite diversity and selection regimes. We also determined host leucocyte differential as this can reveal mechanisms by which injuries influence infections. Theileria infecting zebra was identified using PCR and sequencing of the V4 region of the 18 s rRNA gene and confirmed with phylogenetic analyses. The influence of injury status on parasite infection patterns, genetic diversity and selection were assessed using population genetic tools. Parasitaemia estimated from prevalence and leucocyte differential were determined from microscopic examination of Giemsa stained thin blood smears. Phylogenetic and sequence analyses revealed that the zebra population studied was infected with three Theileria equi haplotypes. Parasitaemia was lower among injured compared to non-injured animals and lower during dry than wet season. Mean (±SD) genetic diversity was 0.386 (±0.128) in injured and 0.513 (±0.144) in non-injured zebra (P = .549). Neutrality tests indicated that T. equi is under strong purifying selection in injured females (Li & Fu's D* = -2.037) and demographic expansion in all zebra during the wet season (Tajima D = -1.904). Injured zebras had a higher median per cent of neutrophils (64% vs 37%) a lower median per cent of basophils (0% vs 1%) and eosinophils (2% vs 4.5%) than non-injured animals, suggesting a heightened immune response and a shift from a Th2 to Th1 T-Cell response favoring the elimination of intracellular parasites in injured animals. This study demonstrates the utility of population genetics in revealing factors influencing parasite diversity and infection patterns.

Resolution of a steroid-resistant, hypereosinophilic immune diathesis with mepolizumab and concomitant amelioration of a mixed thrombotic microangiopathy

The anaphylatoxins produced by an unbridled complement cascade in atypical hemolytic uremic syndrome (aHUS) can alter the leukocyte environment in tissues and peripheral blood, causing clinically significant eosinophilia. While the membrane attack complex and C5a anaphlatoxin can be suppressed with anti-C5 biologics, the production of C3a is still capable of driving a destructive hypereosinophilic syndrome in spite of anticomplement therapy. The side-effects of glucocorticoids in treating hypereosinophilic syndrome limit their therapeutic index in long-term treatment and this behooves the use of alternative strategies. While use of the anti-IL-5 antibody, mepolizumab, has been reported for treatment of primary hypereosinophilic syndromes off-label, its usage in the setting of complement-driven thrombotic microangiopathy has not been attempted. We report mepolizumab's rapid resolution of a glucocorticoid-resistant hypereosinophilic syndrome that caused multi-organ dysfunction in a patient with a complex immune diathesis. The patient's long standing TTP/aHUS disease activity, shown to have direct correlation with his eosinophil count, improved with anti-IL-5 therapy, suggesting a reciprocal enhancement between the conditions.

Flow cytometric analysis of the basophil cell activating impact of potential drug delivery nanoparticle-candidate

INTRODUCTION

Carbon nanotubes – as artificial nano-size ranged materials –have increasing role in the modern biomedical, diagnostic and therapeutic applications.There is a promising option for their use as more potential drug carriers. Despite the favourable properties, their impact (accumulation, elimination, etc.) on biological systems is largely unknown. The main limiting factor of medical use of nanomaterials in most cases is the potential hypersensitive side effect. It can develop in different route, but the activation of basophil granulocytes may play a central role in this process.

OBJECTIVE

Our aim was to test the direct activation ability of different, surface modified nanotubes on basophil granulocytes in vitro. In parallel we tested the effectiveness of BasoTest planned to use for this study.

MATERIALS AND METHODS

Using the blood samples of allergic and healthy volunteers we examined the basophil degranulation in the presence of nanotubes and the expression level changes of cell-surface CD63 on FACS Calibur instrument. Our results were compared to positive(fMLP, Mite, Grass) and negative control samples.

RESULTS

The test we have chosen proved to be sufficiently sensitive and specific for further study. Significant basophil activation was observed in the presence of carbon nanotubes in healthy persons and allergic patients, as well. The activating effect of nanotubes was more prevailed in allergic population.

CONCLUSION

Our experiments have proven the fact that nanotubes may play a role in the development of hypersensitive allergic reactions through their basophil granulocyte activator effect.

The role of basophils in the pathogenesis of allergic disease

There has been much controversy surrounding the importance of basophils in allergy. These cells are, after all, comparatively rare and yet they display remarkable potential to contribute to the symptoms of allergic inflammation. Furthermore, by virtue of their ability to rapidly elaborate T helper type 2 (Th2)-type cytokines, they are well endowed to support ongoing allergic immunity. Despite this, basophils have often been regarded as redundant in this function as in murine models of allergy, their more numerous tissue-fixed mast cell counterparts also display Th2-type cytokine-releasing potential, which is rather different in most human mast cells. Surprisingly, it is from murine models that the basophil has re-surfaced as a key orchestrator of Th2-type immunity and chronic allergic inflammation, a property that has long been hypothesized by researchers into human basophil function but never demonstrated. Moreover, murine experimental models also highlighted the ability of basophils to take up and present antigens in an MHC-dependent manner. Controversy regarding basophils, however, has remained as recent methods for depleting these cells in murine models of allergy and parasitic infection have yielded conflicting results, where the role for this cell oscillates from essential antigen-presenting cells to mere supporting functions in controlling Th2 responses. This review highlights the recent advances in understanding the role of this rather enigmatic cell in allergy.