Influence of ER leak on resting cytoplasmic Ca2+ and receptormediated Ca2+ signalling in human macrophage

Mechanisms controlling endoplasmic reticulum (ER) Ca2+ homeostasis are important regulators of resting cytoplasmic Ca2+ concentration ([Ca2+]cyto) and receptor-mediated Ca2+ signalling. Here we investigate channels responsible for ER Ca2+ leak in THP-1 macrophage and human primary macrophage. In the absence of extracellular Ca2+ we employ ionomycin action at the plasma membrane to stimulate ER Ca2+ leak. Under these conditions ionomycin elevates [Ca2+]cyto revealing a Ca2+ leak response which is abolished by thapsigargin. IP3 receptors (Xestospongin C, 2-APB), ryanodine receptors (dantrolene), and translocon (anisomycin) inhibition facilitated ER Ca2+ leak in model macrophage, with translocon inhibition also reducing resting [Ca2+]cyto. In primary macrophage, translocon inhibition blocks Ca2+ leak but does not influence resting [Ca2+]cyto. We identify a role for translocon-mediated ER Ca2+ leak in receptor-mediated Ca2+ signalling in both model and primary human macrophage, whereby the Ca2+ response to ADP (P2Y receptor agonist) is augmented following anisomycin treatment. In conclusion, we demonstrate a role of ER Ca2+ leak via the translocon in controlling resting cytoplasmic Ca2+ in model macrophage and receptor-mediated Ca2+ signalling in model macrophage and primary macrophage

ATP-evoked intracellular Ca2+ responses in M-CSF differentiated human monocyte-derived macrophage are mediated by P2X4 and P2Y11 receptor activation

Tissues differentially secrete multiple colony stimulating factors under conditions of homeostasis and inflammation, orientating recruited circulating monocytes to differentiate to macrophage with differing functional phenotypes. Here, we investigated ATP-evoked intracellular Ca2+ responses in human macrophage differentiated with macrophage colony-stimulating factor (M-CSF). Extracellular ATP evoked (EC50 13.3 ± 1.4 µM) robust biphasic intracellular Ca2+ responses that showed a dependency on both metabotropic (P2Y) and ionotropic (P2X) receptors. qRT-PCR and immunocytochemistry revealed the expression of P2Y1, P2Y2, P2Y6, P2Y11, P2Y13, P2X1, P2X4, P2X5, and P2X7. Pharmacological analysis revealed contribution of only P2X4 and P2Y11 to the Ca2+ response evoked by maximal ATP concentrations (100 µM). This study reveals the contribution of P2X4 and P2Y11 receptor activation to ATP-evoked intracellular Ca2+ responses, and makes comparison with macrophage differentiated using granulocyte colony-stimulating factor (GM-CSF)

Passive Prophylactic Administration with a Single Dose of Anti-Fel d 1 Monoclonal Antibodies REGN1908-1909 in Cat Allergen-Induced Allergic Rhinitis: A Randomized, Double-blind, Placebo Controlled Trial

RATIONALE: Sensitization to Felis domesticus allergen 1 (Fel d 1) contributes to persistent allergic rhinitis and asthma. Existing treatment options for cat allergy, including allergen immunotherapy (AIT) are only moderately effective, and AIT has limited use due to safety concerns. OBJECTIVES: To explore the relationship among the pharmaokinteic, clinical, and immunological effects of REGN1908-1909 (anti-Fel d 1 monoclonal antibodies) in patients after treatment. METHODS: Patients received REGN1908-1909 (n=36) or placebo (n=37) in a phase 1b study. Fel d 1-induced basophil and IgE-facilitated allergen binding responses were evaluated at baseline and days 8, 29 and 85. Cytokine and chemokine levels in nasal fluids were measured. REGN1908-1909 inhibition of allergen-IgE binding in patient serum was evaluated. MEASUREMENTS AND MAIN RESULTS: Peak serum drug concentrations were concordant with maximal observed clinical response. The anti-Fel d 1 IgE/cat-dander IgE ratio in pretreatment serum correlated with Total Nasal Symptom Score improvement. The allergen neutralizing capacity of REGN1908-1909 was observed in serum and nasal fluid, and was detected in an inhibition assay. Type-2 cytokines (IL-4, IL-5 and IL-13) and chemokines (CCL17/TARC, CCL5/RANTES) in nasal fluid were inhibited in REGN1908-1909-treated patients compared to placebo (all P < 0.05); IL-13 and IL-5 levels correlated with TNSS improvement. Ex vivo assays demonstrated that REGN1908 and REGN1909 combined was more potent than each alone for inhibiting FcεRI- and FcεRII (CD23)-mediated allergic responses and subsequent T-cell activation. CONCLUSION: Single passive dose administration of Fel d 1-neutralizing IgG antibodies improved nasal symptoms in cat-allergic patients, and was underscored by suppression of FcεRI-, FcεRII- and Th2-mediated allergic responses. Clinical trial registration available at www.clinicaltrials.gov, ID: NCT02127801

Allergen-specific IgG+ memory B cells are temporally linked to IgE memory responses

BACKGROUND: Immunoglobulin E (IgE) are least abundant, tightly regulated and IgE producing B cells are rare. The cellular origin and evolution of IgE responses are poorly understood. OBJECTIVE: To investigate the cellular and clonal origin of IgE memory responses following mucosal allergen exposure by sublingual immunotherapy (SLIT). METHODS: In a randomized double-blind, placebo-controlled, time-course SLIT study, peripheral blood mononuclear cells (PBMCs) and nasal biopsies were collected from forty adults with seasonal allergic rhinitis at baseline, 4, 8, 16, 28 and 52 weeks. RNA was extracted from PBMCs, sorted B cells and nasal biopsies for VH repertoire sequencing. Moreover, monoclonal antibodies were derived from single B cell transcriptomes. RESULTS: Combining VH repertoire sequencing and single cell transcriptomics yielded direct evidence of a parallel boost of two clonally and functionally related B cell subsets of short-lived IgE+ plasmablasts and IgG+ memory B cells (termed IgGE). Mucosal grass pollen allergen exposure by SLIT resulted in highly diverse IgE and IgGE repertoires. These were extensively mutated and appeared relative stable as per heavy chain isotype, somatic hypermutations and clonal composition. Single IgGE + memory B cell and IgE+ pre-plasmablast transcriptomes encoded antibodies that were specific for major grass pollen allergens and were able to elicit basophil activation at very low allergen concentrations. CONCLUSION: For the first time, we have shown that upon mucosal allergen exposure, human IgE memory resides in allergen-specific IgG+ memory B cells. These rapidly switch isotype and expand into short-lived IgE+ plasmablasts and serve as a potential target for therapeutic intervention

ATP Evokes Ca2+ Responses and CXCL5 Secretion via P2X4 Receptor Activation in Human Monocyte-Derived Macrophages

Leukocytes sense extracellular ATP, a danger-associated molecular pattern, released during cellular stress and death, via activation of cell surface P2X and P2Y receptors. Here, we investigate P2 receptor expression in primary human monocyte-derived macrophages and receptors that mediate ATP-evoked intracellular [Ca2+]i signals and cytokine production in response to ATP concentrations that exclude P2X7 receptor activation. Expression of P2X1, P2X4, P2X5, P2X7, P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, and P2Y13 was confirmed by quantitative RT-PCR and immunocytochemistry. ATP elicited intracellular Ca2+ responses in a concentration-dependent fashion (EC50 = 11.4 ± 2.9 μM, n = 3). P2Y11 and P2Y13 activations mediated the amplitude of [Ca2+]i response, whereas P2X4 activation, but not P2X1 or P2X7, determined the duration of Ca2+ response during a sustained phase. ATP mediated gene induction of CXCL5, a proinflammatory chemokine. P2X4 antagonism (PSB-12062 or BX430) inhibited ATP-mediated induction of CXCL5 gene expression and secretion of CXCL5 by primary macrophage. Inhibition of CXCL5 secretion by P2X4 antagonists was lost in the absence of extracellular Ca2+. Reciprocally, positive allosteric modulation of P2X4 (ivermectin) augmented ATP-mediated CXCL5 secretion. P2X7, P2Y11, or P2Y13 receptor did not contribute to CXCL5 secretion. Together, the data reveals a role for P2X4 in determining the duration of ATP-evoked Ca2+ responses and CXCL5 secretion in human primary macrophage

Induction of IL-10-producing type 2 innate lymphoid cells by allergen immunotherapy is associated with clinical response

The role of innate immune cells in allergen immunotherapy that confers immune tolerance to the sensitizing allergen is unclear. Here, we report a role of interleukin-10-producing type 2 innate lymphoid cells (IL-10+ ILC2s) in modulating grass-pollen allergy. We demonstrate that KLRG1+ but not KLRG1– ILC2 produced IL-10 upon activation with IL-33 and retinoic acid. These cells attenuated Th responses and maintained epithelial cell integrity. IL-10+ KLRG1+ ILC2s were lower in patients with grass-pollen allergy when compared to healthy subjects. In a prospective, double-blind, placebo-controlled trial, we demonstrated that the competence of ILC2 to produce IL-10 was restored in patients who received grass-pollen sublingual immunotherapy. The underpinning mechanisms were associated with the modification of retinol metabolic pathway, cytokine-cytokine receptor interaction, and JAK-STAT signaling pathways in the ILCs. Altogether, our findings underscore the contribution of IL-10+ ILC2s in the disease-modifying effect by allergen immunotherapy

Induction of IL-10-producing type 2 innate lymphoid cells by allergen immunotherapy is associated with clinical response

The role of innate immune cells in allergen immunotherapy that confers immune tolerance to the sensitizing allergen is unclear. Here, we report a role of interleukin-10-producing type 2 innate lymphoid cells (IL-10+ ILC2s) in modulating grass-pollen allergy. We demonstrate that KLRG1+ but not KLRG1– ILC2 produced IL-10 upon activation with IL-33 and retinoic acid. These cells attenuated Th responses and maintained epithelial cell integrity. IL-10+ KLRG1+ ILC2s were lower in patients with grass-pollen allergy when compared to healthy subjects. In a prospective, double-blind, placebo-controlled trial, we demonstrated that the competence of ILC2 to produce IL-10 was restored in patients who received grass-pollen sublingual immunotherapy. The underpinning mechanisms were associated with the modification of retinol metabolic pathway, cytokine-cytokine receptor interaction, and JAK-STAT signaling pathways in the ILCs. Altogether, our findings underscore the contribution of IL-10+ ILC2s in the disease-modifying effect by allergen immunotherapy

EAACI Allergen Immunotherapy User's Guide

Allergen immunotherapy is a cornerstone in the treatment of allergic children. The clinical efficiency relies on a well-defined immunologic mechanism promoting regulatory T cells and downplaying the immune response induced by allergens. Clinical indications have been well documented for respiratory allergy in the presence of rhinitis and/or allergic asthma, to pollens and dust mites. Patients who have had an anaphylactic reaction to hymenoptera venom are also good candidates for allergen immunotherapy. Administration of allergen is currently mostly either by subcutaneous injections or by sublingual administration. Both methods have been extensively studied and have pros and cons. Specifically in children, the choice of the method of administration according to the patient's profile is important. Although allergen immunotherapy is widely used, there is a need for improvement. More particularly, biomarkers for prediction of the success of the treatments are needed. The strength and efficiency of the immune response may also be boosted by the use of better adjuvants. Finally, novel formulations might be more efficient and might improve the patient's adherence to the treatment. This user's guide reviews current knowledge and aims to provide clinical guidance to healthcare professionals taking care of children undergoing allergen immunotherapy.</p