Evaluation of CCR3 as a basophil activation marker

Eosinophils, basophils and myeloid-derived suppressor cells in chronic Loa loa infection and its treatment in an endemic setting

BACKGROUND

Chronic infection by Loa loa remains an unsolved immunological paradox. Despite harboring subcutaneously migrating adult worms and often high densities of microfilariae, most patients experience only relatively mild symptoms, yet microfilaricidal treatment can trigger life-threatening inflammation. Here, we investigated innate cell populations hypothesized to play a role in these two faces of the disease, in an endemic population in Gabon.

METHODOLOGY/PRINCIPAL FINDINGS

We analyzed numbers and activation of eosinophils and basophils, as well as myeloid-derived suppressor cell (MDSC) subsets and associated circulating cytokine levels by flow cytometry in sex- and age-matched L. loa-uninfected (LL-), -amicrofilaraemic (MF-) and -microfilaraemic (MF+) individuals (n = 42), as well as microfilaraemic individuals treated with albendazole (n = 26). The percentage of eosinophils was lower in LL- (3.0%) than in the combined L. loa-infected population, but was similar in MF+ (13.1%) and MF- (12.3%). Upon treatment of MF+, eosinophilia increased from day 0 (17.2%) to day 14 (24.8%) and had decreased below baseline at day 168 (6.3%). Expression of the eosinophil activation marker CD123 followed the same pattern as the percentage of eosinophils, while the inverse was observed for CD193 and to some extent CD125. Circulating IL-5 levels after treatment followed the same pattern as eosinophil dynamics. Basophil numbers did not differ between infection states but increased after treatment of MF+. We did not observe differences in MDSC numbers between infection states or upon treatment.

CONCLUSIONS/SIGNIFICANCE

We demonstrate that both chronic infection and treatment of L. loa microfilaraemia are associated with eosinophil circulation and distinct phenotypical activation markers that might contribute to inflammatory pathways in this setting. In this first ever investigation into MDSC in L. loa infection, we found no evidence for their increased presence in chronic loiasis, suggesting that immunomodulation by L. loa is induced through other pathways.

Towards standardizing basophil identification by flow cytometry

Background

Basophils normally make up <2% of the white blood cells (WBC). There is no clear consensus for basophil identification by flow cytometry. The increased demand for basophil activation test (BAT) to identifying and monitoring allergic patients highlights the need for a standardized approach to identify basophils.

Methods

Using flow cytometry we analyzed whole blood stained with antibodies against: IgE, CD123, CD193, CD203c, CD3, HLADR, FcɛRI, CRTH2 and CD45. We examined unstimulated blood as well as blood stimulated with Anti-IgE and fMLP. Finally, we compared the results to a complete blood count (CBC) from an FDA approved hematological analyzer.

Results

Basophil identification relying on just one surface marker performed worse than approaches utilizing two identification markers. The percentage of basophils from WBC determined by flow cytometry results had a good correlation with the CBC results even though the CBC results were generally higher. Stimulating whole blood with the basophil activators did not interfere with the basophil identification markers.

Conclusion

In flow cytometry assays, two surface markers should be used for identifying basophils and if a very pure basophil fraction is desired a third marker can be considered. In our hands the approaches that included CD123 in combination with either CD193, HLADR^negative or FcɛRI performed the best.

Menthone Inhalation Alleviates Local and Systemic Allergic Inflammation in Ovalbumin-Sensitized and Challenged Asthmatic Mice

Menthone is rich in Mentha × Piperita L. essential oil and it has anti-inflammatory properties; research shows that it is useful, via percutaneous absorption, in treating inflammation-related diseases. However, anti-allergic inflammatory effects of volatile menthone have not yet been used to treat allergic asthma, in vivo. We hypothesized that menthone inhalation may have anti-inflammatory and anti-allergic effects in patients with allergic asthma. Therefore, in our study, menthone inhalation was used to treat ovalbumin (OVA)-sensitized and challenged asthmatic mice. Allergic inflammation mediator changes in the lungs and airways, sera, splenocytes, and peritoneal macrophages of the mice were measured. Relative expression amounts of six receptor genes related to allergic inflammation of the lungs and airways were quantitated using a two-step real time quantitative polymerase chain reaction (qPCR). Results showed that menthone inhalation increased serum OVA-specific IgG2a/IgG1 and IgG2a/IgE ratios, increased Th1-type cytokine production in the bronchoalveolar lavage fluid, and decreased nitric oxide, protein, and eotaxin levels. Menthone inhalation inhibited mast cell and eosinophil degranulation, and chemokine (C-C motif) receptor 3 (Ccr3) gene expression amounts, but (relatively) increased Th1 cytokine secretion by splenocytes. Our results evidence that menthone inhalation alleviates local and systemic allergic inflammation in asthmatic mice.

Innovative robust basophil activation test using a novel gating strategy reliably diagnosing allergy with full automation

BACKGROUND

Allergy is one of the most common chronic diseases in Europe. Therefore, an increased need for specific and sensitive diagnostic tests that truly detect allergy exists. This study aimed at establishing a highly specific high-throughput and automated basophil activation test (BAT) that proves the existence of an allergy with utmost probability.

METHODS

BAT from 1104 samples was analyzed; a novel gating strategy with three antibodies (FcεRIα, CD203c, CD63) was established and compared with our published protocol (12 antibodies). Based on the novel gating strategy, storage conditions, automated measurement, and analyses using R (1376 samples out of 1389) were optimized to set up a high-throughput BAT.

RESULTS

No differences in sensitivity and specificity were found between the novel three antibody (FcεRIα, CD203c, CD63) and the 12 antibody gating strategy or between automated and manually analyzed samples (saving up to 90% of labor time). The time frame for basophil activation measurement after blood donation has been extended considerably (whole blood storage ≤7 days (RT) and 17 days (4°C) prior to BAT preparation and measurement). Respective storage conditions were optimized for samples after stimulation, staining, and preparation (≤7 days (RT) and 28 days (4°C)). These achievements were confirmed by a nationwide ring trial showing robustness and applicability of our BAT on a variety of flow cytometers.

CONCLUSION

Our considerable optimizations overcame the hurdles that until now prevented the BAT from being used as high-throughput allergy diagnostic test in routine laboratories and shall allow for collaborative studies between clinics and research centers.

Behind the scenes with basophils: an emerging therapeutic target

Though basophils were originally viewed as redundant blood ‘mast cells’, the implementation of flow cytometry has established basophils as unique leukocytes with critical immunomodulatory functions. Basophils play an active role in allergic inflammation, autoimmunity, and hematological malignancies. They are distinguishable from other leukocytes by their characteristic metachromatic deep-purple cytoplasmic, round granules. Mature basophils are phenotypically characterized by surface expression of IL-3Rα (CD123); IL-3 drives basophil differentiation, degranulation, and synthesis of inflammatory mediators including type 2 cytokines. Basophil degranulation is the predominant source of histamine in peripheral blood, promoting allergic responses. Basophils serve as a bridge between innate and adaptive immunity by secreting IL-4 which supports eosinophil migration, monocyte differentiation into macrophages, B-cell activation, and CD4 T-cell differentiation into Th2 cells. Further, basophilia is a key phenomenon in myeloid neoplasms, especially chronic myeloid leukemia (CML) for which it is a diagnostic criterion. Increased circulating basophils, often with aberrant immunophenotype, have been detected in patients with CML and other myeloproliferative neoplasms (MPNs). The significance of basophils’ immunoregulatory functions in malignant and non-malignant diseases is an active area of research. Ongoing and future research can inform the development of immunotherapies that target basophils to impact allergic, autoimmune, and malignant disease states. This review article aims to provide an overview of basophil biology, identification strategies, and roles and dysregulation in diseases.

CCR3-shRNA promotes apoptosis and inhibits chemotaxis and degranulation of mouse mast cells

Mast cells (MCs) are the major effector cells of allergic rhinitis (AR). The present study aimed to investigate the effects of C-C chemokine receptor type 3 (CCR3) on the proliferation, apoptosis, chemotaxis and activated degranulation of mouse MCs. Mouse bone marrow-derived MCs were cultured in vitro, purified and identified using toluidine blue staining and flow cytometry. Three different CCR3-short hairpin (shRNA) lentiviral vectors were constructed and transfected into MCs, and the mRNA and protein expression levels of CCR3 were assessed by reverse transcription-quantitative PCR and western blotting. Proliferation and apoptosis of the MCs were measured using Cell Counting kit-8 (CCK-8) assays and flow cytometry, respectively. MC chemotaxis was assessed by Transwell assay and quantified using flow cytometry. The activation of MC degranulation was examined using ELISAs. The results demonstrated that MCs were appropriately isolated, and identified that CCR3-shRNA2 presented the higher knockdown effect among the three shRNAs tested. Following 96 h of transfection, the results of CCK-8 and flow cytometry assays demonstrated that CCR3-shRNA2 inhibited MC proliferation and promoted MC apoptosis. The results from the Transwell assay indicated that CCR3-shRNA2 restrained MC chemotaxis, whereas ELISA results demonstrated that CCR3-shRNA2 suppressed MC degranulation. In conclusion, CCR3-shRNA2 effectively downregulated CCR3 mRNA and protein expression levels in mouse MCs. In addition, CCR3-shRNA2 promoted MC apoptosis and suppressed the proliferation, chemotaxis and degranulation of mouse MCs, suggesting that CCR3-shRNA2 may serve as a therapeutic tool for the treatment of allergic rhinitis.