IL-3 inhibits rat osteoclast differentiation induced by TNF-α and other pro-osteoclastogenic cytokines.

IL-3, a haematopoiesis regulatory factor, has previously been shown to inhibit both mouse and human osteoclast differentiation and bone resorption. Here, the role of rat IL-3 on rat osteoclast differentiation was evaluated to address whether the inhibitory action of IL-3 on osteoclastogenesis is conserved in various species. It was observed that IL-3 inhibited rat osteoclast differentiation induced by both TNF-α and receptor activator of NF-ĸB ligand (RANKL). TNF-α is known to induce bone loss in postmenopausal osteoporotic women and it also synergise with many pro-osteoclastogenic cytokines to cause huge pathological bone loss. Importantly, it was found that rat IL-3 inhibits the synergistic action of TNF-α with RANKL and IL-1ß, TGFß1 and TGF-ß3. IL-3 downregulates the TNF-α-induced nuclear translocation of NF-ĸB-p65 and c-fos without affecting c-jun. Interestingly, we observed that IL-3 also inhibits osteoclast differentiation in vivo in rats induced by TNF-α. All these results suggest that inhibitory action of IL-3 on osteoclastogenesis is conserved in various species including mice, rats and humans. Thus, our results clearly indicate that IL-3 has therapeutic potential to treat pathological bone loss in important skeletal diseases.

The Inflammatory Cytokine IL-3 Hampers Cardioprotection Mediated by Endothelial Cell-Derived Extracellular Vesicles Possibly via Their Protein Cargo.

The biological relevance of extracellular vesicles (EV) released in an ischemia/reperfusion setting is still unclear. We hypothesized that the inflammatory microenvironment prevents cardioprotection mediated by endothelial cell (EC)-derived extracellular vesicles. The effects of naïve EC-derived EV (eEV) or eEV released in response to interleukin-3 (IL-3) (eEV-IL-3) were evaluated in cardiomyoblasts (H9c2) and rat hearts. In transwell assay, eEV protected the H9c2 exposed to hypoxia/reoxygenation (H/R) more efficiently than eEV-IL-3. Conversely, only eEV directly protected H9c2 cells to H/R-induced damage. Consistent with this latter observation, eEV, but not eEV-IL-3, exerted beneficial effects in the whole heart. Protein profiles of eEV and eEV-IL-3, established using label-free mass spectrometry, demonstrated that IL-3 drives changes in eEV-IL-3 protein cargo. Gene ontology analysis revealed that both eEV and eEV-IL-3 were equipped with full cardioprotective machinery, including the Nitric Oxide Signaling in the Cardiovascular System. eEV-IL-3 were also enriched in the endothelial-nitric oxide-synthase (eNOS)-antagonist caveolin-1 and proteins related to the inflammatory response. In vitro and ex vivo experiments demonstrated that a functional Mitogen-Activated Protein Kinase Kinase (MEK1/2)/eNOS/guanylyl-cyclase (GC) pathway is required for eEV-mediated cardioprotection. Consistently, eEV were found enriched in MEK1/2 and able to induce the expression of B-cell-lymphoma-2 (Bcl-2) and the phosphorylation of eNOS in vitro. We conclude that an inflammatory microenvironment containing IL-3 changes the eEV cargo and impairs eEV cardioprotective action.

SS30, a novel thioaptamer targeting CD123, inhibits the growth of acute myeloid leukemia cells.

AIMS: CD123 represents an important acute myeloid leukemia (AML) therapeutic target. CD123 aptamers may potentially serve as tumor-homing ligands with excellent affinity and specificity for AML targeted therapy, but their complexity, laborious preparation and nuclease digestion limited pharmacological application. The aim of this study was to develop the first CD123 thioaptamer to overcome these obstacles. MAIN METHODS: Flow cytometry was utilized to assess the binding specificity, affinity and anti-nuclease ability of thioaptamer. CCK8, Annexin-V/DAPI, and colony forming assays were used to evaluate the anti-cancer ability of thioaptamer in vitro. The tumor volume, weights, survival rate, H&E staining of organs, and serum level of organ damage biomarkers of animal model were applied to investigate the anti-cancer ability of thioaptamer in vivo. Furthermore, we explored the binding mechanism between thioaptamer and CD123. KEY FINDINGS: CD123 thioaptamer SS30 was able to bind to CD123 structure with high specificity in complex nuclease environment, the dissociation constant of 39.1 nM for CD123 peptide and 287.6 nM for CD123+ AML cells, while exhibiting minimal cross-reactivity to albumin. Furthermore, SS30 inhibited the proliferation and survival of AML cell lines and human AML blasts selectively in vitro (P < 0.01). In addition, SS30 prolonged the survival and inhibited tumor growth in a mouse xenograft tumor model in vivo. Of note, SS30 blocked the interaction between IL-3 and CD123, and decreased expression of p-STAT5 and p-AKT. SIGNIFICANCE: The proliferation inhibition and nuclease resistance ability of SS30 made it as a more promising functional molecule for AML targeted therapy.

Thrombopoietin contributes to the formation and the maintenance of hematopoietic progenitor-containing cell clusters in the aorta-gonad-mesonephros region.

In the midgestation mouse embryo, hematopoietic cell clusters containing hematopoietic stem/progenitor cells arise in the aorta-gonad-mesonephros (AGM) region. We have previously reported that forced expression of the Sox17 transcription factor in CD45lowc-Kithigh AGM cells, which are the hematopoietic cellular component of the cell clusters, and subsequent coculture with OP9 stromal cells in the presence of three cytokines, stem cell factor (SCF), interleukin-3 (IL-3), and thrombopoietin (TPO), led to the formation and the maintenance of cell clusters with cells at an undifferentiated state in vitro. In this study, we investigated the role of each cytokine in the formation of hematopoietic cell clusters. We cultured Sox17-transduced AGM cells with each of the 7 possible combinations of the three cytokines. The size and the number of Sox17-transduced cell clusters in the presence of TPO, either alone or in combination, were comparable to that observed with the complete set of the three cytokines. Expression of TPO receptor, c-Mpl was almost ubiquitously expressed and maintained in Sox17-transduced hematopoietic cell clusters. In addition, the expression level of c-Mpl was highest in the CD45lowc-Kithigh cells among the Sox17-transduced cell clusters. Moreover, c-Mpl protein was highly expressed in the intra-aortic hematopoietic cell clusters in comparison with endothelial cells of dorsal aorta. Finally, stimulation of the endothelial cells prepared from the AGM region by TPO induced the production of hematopoietic cells. These results suggest that TPO contributes to the formation and the maintenance of hematopoietic cell clusters in the AGM region.

The role of IL-11 in immunity and cancer.

Interleukin-11 (IL-11) is a member of the glycoprotein-130 (GP-130) cytokines that utilizes the GP-130 signaling pathway shared by other cytokines of the same family. Traditionally regarded as an anti-inflammatory cytokine, IL-11 also demonstrates its role as a proinflammatory cytokine, suggesting its complex role in immune response. In recent years, IL-11 has an emerging role in various inflammation-associated cancers. In this review, we aim to discuss IL-11 signaling pathway, to explore the role of IL-11 in immunity and various cancers, and to provide a therapeutic perspective of strategies utilized to interfere IL-11 signaling in cancer cells.

Enhancement of the cytotoxic activity of cytokine-induced killer cells transfected with IL3PE38KDEL gene against acute myeloid leukemia cells.

Cytokine-induced killer (CIK) cells, one of the feasible and effective methods of adoptive immunotherapy, have shown anti-leukemia activity in vivo and in vitro. But the strategy exhibits limited cytotoxic activity in clinical studies. In this study, CIK cells were transfected with an interleukin-3/Pseudomonas exotoxin gene (IL3PE38KDEL). RT-PCR and ELISA were used to verify the expression of IL3PE38KDEL in the transfected CIK cells. These cells released 1,186.7 ± 149.6 pg IL3PE38KDEL/10(4) cells over 48 h into the medium and the culture supernatant selectively killed IL3 receptor(IL3R)-positive HL60 cells, but not IL3R-negative K562 cells. Moreover, IL3PE38KDEL transfection did not influence phenotypes and cytokine production of CIK cells. Co-cultured with leukemia cells, IL3PE38KDEL transfected CIK cells showed enhanced cytotoxicity against IL3R-positive HL60 cells at all effector-to-target (E:T) ratios, but exerted a basal anti-leukemia activity against IL3R-negative K562 cells. Our findings demonstrate that IL3PE38KDEL gene transfection may be a novel strategy for improving anti-leukemia activity of CIK cells.

Interrelationship between IL-3 and mast cells.

It is well established that mast cells, which are found in the tissues in the proximity of small blood vessels and post-capillary venules, play a key role in the early phase of IgE-mediated allergic reactions. A greatly expanded understanding of the biology of IL-3 has emerged since the early 1980s. IL-3 is a specific factor that stimulates the growth of hematopoietic stem and progenitor cells of a variety of lineages and can promote the proliferation of certain classes of lymphocytes distinct from those that are dependent on IL-2. IL-3 has been identified among the most important cytokines for regulation of mast cell growth and differentiation, migration and effector function activities of many hematopoietic cells. IL-3 termed multi colony-stimulating-factor (multi-CSF) or mast cell growth factor (MCGF) is a haematopoietic growth factor which stimulates the formation of colonies for erythroid, megakaryocytic, granulocytic and monocytic lineages. It is predominantly produced by activated T cells, natural killer (NK) cells and mast cells and supports the growth-promoting effects of SCF on mast cell precursors. IL-3 causes severe hypersensivity reactions and plays a pivotal role in exacerbating the inflammatory response in vivo. Here we report the interrelationship between IL-3 and mast cells.

Basophils are rapidly mobilized following initial aeroallergen encounter in naïve mice and provide a priming source of IL-4 in adaptive immune responses.

Chronic aeroallergen inhalation elicits the expansion of IL-4-producing Th2 cells and the production of IgE antibodies. In sensitized subjects, who have established IgE and Th2 responses, re-exposure to allergen leads to rapid recruitment of basophils, which are thought to be important effectors of late phase allergic reactions. Several investigations of responses to parasites and injected antigens have identified an additional role for basophils as innate immune effectors during initial antigen encounter in immunologically naïve hosts. These cells constitutively express IL-4 and promote Th2 polarized adaptive responses to such antigens. Their early recruitment and modulation of cellular immune responses to natural inhaled allergens in the airways has been scarcely investigated. In this study, basophils were enumerated in lung tissue, blood and spleen from BALB/c mice in the first days after inhalation of an aqueous extract of the allergen, Aspergillus fumigatus (Af). Af inhalation induced rapid increases in basophil numbers in the lung, blood and spleen. This was Rag-1-, MyD88- and IL-3-independent. The basophils expressed abundant IL-4. Their depletion during Af sensitization resulted in an attenuated induction of both IL-4 producing Th lymphocytes and specific IgE and IgG1 responses to an inhaled protein antigen, ovalbumin, which was co-administered. Our results suggest that basophils are rapidly recruited to the airways of naïve mice following initial fungal allergen exposure, produce IL-4 and influence the development of the adaptive immune response.

Genome-wide pathway analysis in neuroblastoma.

The aim of this study was to identify candidate single-nucleotide polymorphisms (SNPs) that might play a role in susceptibility to neuroblastoma, elucidate their potential mechanisms, and generate SNP-to-gene-to-pathway hypotheses. A genome-wide association study (GWAS) dataset of neuroblastoma that included 442,976 SNPs from 1,627 neuroblastoma patients and 3,254 control subjects of European descent was used in this study. The identify candidate causal SNPs and pathways (ICSNPathway) analysis was applied to the GWAS dataset. ICSNPathway analysis identified 15 candidate SNPs, 10 genes, and 31 pathways, which revealed 10 hypothetical biological mechanisms. The strongest hypothetical biological mechanism was one wherein SNPrs40401 modulates the role of IL3 in several pathways and conditions, including the stem pathway, asthma (hsa05310), the dendritic cell pathway, and development (0.001 < p < 0.004; 0.001 < FDR < 0.033). The second strongest mechanism identified was that in which rs1048108 and rs16852600 alter the function of BARD1, which negatively regulates developmental process and modulates processes including cell development and programmed cell death (0.001 < p < 0.004; 0.001 < FDR < 0.033). The third mechanism identified was one wherein rs1939212 modulated CFL1, resulting in negative regulation of development, cell death, neural crest cell migration, and apoptosis (0.001 < p < 0.004; 0.001 < FDR < 0.033). By using the ICSNPathway to analyze neuroblastoma GWAS data, 15 candidate SNPs, 10 genes including IL3, BARD1, and CFL, and 31 pathways were identified that might contribute to the susceptibility of patients to neuroblastoma.

Interleukin-3 plays dual roles in osteoclastogenesis by promoting the development of osteoclast progenitors but inhibiting the osteoclastogenic process.

Interleukin (IL)-3, a multilineage hematopoietic growth factor, is implicated in the regulation of osteoclastogenesis. However, the role of IL-3 in osteoclastogenesis remains controversial; whereas early studies showed that IL-3 stimulates osteoclastogenesis, recent investigations demonstrated that IL-3 inhibits osteoclast formation. The objective of this work is to further address the role of IL-3 in osteoclastogenesis. We found that IL-3 treatment of bone marrow cells generated a population of cells capable of differentiating into osteoclasts in tissue culture dishes in response to the stimulation of the monocyte/macrophage-colony stimulating factor (M-CSF) and the receptor activator of nuclear factor kappa B ligand (RANKL). The IL-3-dependent hematopoietic cells were able to further proliferate and differentiate in response to M-CSF stimulation and the resulting cells were also capable of forming osteoclasts with M-CSF and RANKL treatment. Interestingly, IL-3 inhibits M-CSF-/RANKL-induced differentiation of the IL-3-dependent hematopoietic cells into osteoclasts. The flow cytometry analysis indicates that while IL-3 treatment of bone marrow cells slightly affected the percentage of osteoclast precursors in the surviving populations, it considerably increased the percentage of osteoclast precursors in the populations after subsequent M-CSF treatment. Moreover, osteoclasts derived from IL-3-dependent hematopoietic cells were fully functional. Thus, we conclude that IL-3 plays dual roles in osteoclastogenesis by promoting the development of osteoclast progenitors but inhibiting the osteoclastogenic process. These findings provide a better understanding of the role of IL-3 in osteoclastogenesis.

High yield production of a soluble human interleukin-3 variant from E. coli with wild-type bioactivity and improved radiolabeling properties.

Human interleukin-3 (hIL-3) is a polypeptide growth factor that regulates the proliferation, differentiation, survival and function of hematopoietic progenitors and many mature blood cell lineages. Although recombinant hIL-3 is a widely used laboratory reagent in hematology, standard methods for its preparation, including those employed by commercial suppliers, remain arduous owing to a reliance on refolding insoluble protein expressed in E. coli. In addition, wild-type hIL-3 is a poor substrate for radio-iodination, which has been a long-standing hindrance to its use in receptor binding assays. To overcome these problems, we developed a method for expression of hIL-3 in E. coli as a soluble protein, with typical yields of >3mg of purified hIL-3 per litre of shaking microbial culture. Additionally, we introduced a non-native tyrosine residue into our hIL-3 analog, which allowed radio-iodination to high specific activities for receptor binding studies whilst not compromising bioactivity. The method presented herein provides a cost-effective and convenient route to milligram quantities of a hIL-3 analog with wild-type bioactivity that, unlike wild-type hIL­3, can be efficiently radio-iodinated for receptor binding studies.

RAF and antioxidants prevent cell death induction after growth factor abrogation through regulation of Bcl-2 proteins.

We have shown previously that mitochondrial ROS production is essential to turn growth factor (GF) removal into cell death. Activated RAF, AKT, Bcl-2 and antioxidants protected equally well against ROS accumulation and subsequent death. Here we investigated whether protection by survival signaling and antioxidants utilizes shared or distinct targets. Using serum deprivation from NIH 3T3 fibroblasts and IL-3 withdrawal from promyeloid 32D cells, we showed that pro-survival signaling by activated RAF but not AKT prevented the decline in Mcl-1 following GF abrogation. GF starvation increased levels of Bim in both model systems, which was prevented by RAF in 32D cells but not in NIH 3T3 fibroblasts. RAF and AKT suppressed activation and mitochondrial translocation of BAX. Also, antioxidant treatment efficiently prevented BAX activation and death of 32D cells but showed little effect on its mitochondrial translocation. No significant impact of antioxidant treatment on Bim or Mcl-1 expression was observed. ROS produced during GF abrogation also did not alter the activity of intracellular signaling pathways, which have been implicated previously in cell killing by pro-oxidants. Together these data suggest Bcl-2 family proteins as convergence point for RAF and ROS in life and death decisions.

Signalling by the ßc family of cytokines.

The GM-CSF, IL-3 and IL-5 family of cytokines, also known as the ßc family due to their receptors sharing the signalling subunit ßc, regulates multiple biological processes such as native and adaptive immunity, inflammation, normal and malignant hemopoieis, and autoimmunity. Australian scientists played a major role in the discovery and biological characterisation of the ßc cytokines and their recent work is revealing unique features of cytokine receptor assembly and signalling. Furthermore, specific antibodies have been generated to modulate their function. Characterisation of the structural and dynamic requirements for the activation of the ßc receptor family and the molecular definition of downstream signalling pathways are providing new insights into cytokine receptor signalling as well as new therapeutic opportunities.

Trib3 is regulated by IL-3 and affects bone marrow-derived mast cell survival and function.

Mast cells are the principal effectors of IgE-mediated immune responses, including allergic reactions. Tribbles homolog 3 (Trib3) encodes a pseudokinase implicated in the cellular stress response and has been linked to inflammation in certain situations. Here we report the role of Trib3 in mouse bone marrow-derived mast cells (BMMCs). Our results show that Trib3 mRNA expression in BMMCs is positively regulated by the growth factor interleukin (IL)-3. BMMCs originating from Trib3 knockout mice demonstrate unaltered differentiation kinetics and cell surface expression of mast cell markers. When challenged with transient IL-3 deprivation, Trib3-deficient BMMCs display delayed recovery, and during prolonged IL-3 starvation, cell death is accelerated in Trib3-null cultures. IgE-dependent and pharmacologically induced degranulation is impaired in Trib3-deficient BMMCs, as is activation-induced cytokine mRNA expression. Thus, Trib3 contributes to the survival and activity of primary cultured mast cells, which suggests a role for Trib3 in the modulation of the immune response.

Up-regulation of IL-33 expression in various types of murine cells by IL-3 and IL-4.

The crucial roles of the novel cytokine IL-33 in allergic, inflammatory, infectious and autoimmune diseases are becoming characterized. However, the cytokines which regulate IL-33 expression and secretion are still largely unknown. In this study, IL-3 and IL-4 were found to up-regulate IL-33 mRNA expression in mouse peritoneal exudate cells by a two-color DNA microarray and further confirmed by real time PCR and ELISA. IL-3 and IL-4 synergistically promote IL-33 mRNA expression and IL-33 intracrine in the heterogeneous cell populations as peritoneal exudates cells, bone marrow cells and splenic cells. IL-3 and IL-4 also induced IL-33 introcrine in the peritoneal exudate cells from the macrophage-deficient op/op mice, suggesting that macrophage is not the only target of IL-3 and IL-4 in the heterogeneous peritoneal exudate cells. Furthermore, IL-3 and IL-4 were verified to promote the IL-33 intracrine in the homogeneous cell population as fibroblasts and mast cells. These results indicate that up-regulation of IL-33 expression by IL-3 and IL-4 is not a feature particular to a specific type of cells. Up to 100 cytokines were screened, but none of them stimulated the secretion or release of IL-33 in the culture system. In summary, we confirm for the first time that IL-3 and IL-4 are critical for IL-33 intracrine in murine cells of various types, indicating that IL-3 and IL-4 may play an important role in the constitutive expression of IL-33 in vivo.

IL-3 promotes osteoblast differentiation and bone formation in human mesenchymal stem cells.

IL-3 is an important cytokine that regulates hematopoiesis. We have previously demonstrated that IL-3 is a potent inhibitor of osteoclastogenesis and bone resorption. In the present study, we have investigated the role of IL-3 on human osteoblast differentiation and bone formation. We found that IL-3 in a dose-dependent manner increases osteoblast differentiation and matrix mineralization in human mesenchymal stem cells (MSCs). IL-3 significantly enhances the expression of osteoblast specific genes such as alkaline phosphatase, collagen type-I, osteocalcin and osteopontin; and Runx-2 and osterix transcription factors. Moreover, IL-3 induces the expression of bone morphogenetic protein-2 (BMP-2), and activates smad1/5/8. IL-3 enhances osteoblast differentiation and BMP-2 secretion through JAK/STAT pathway. Interestingly, IL-3 promotes in vivo bone regeneration ability of MSCs. Thus, we reveal for the first time that IL-3 enhances human osteoblast differentiation and bone formation in both in vitro and in vivo conditions, and suggest its therapeutic potential for bone formation in important bone diseases.

Chemoattractant-induced signaling via the Ras-ERK and PI3K-Akt networks, along with leukotriene C4 release, is dependent on the tyrosine kinase Lyn in IL-5- and IL-3-primed human blood eosinophils.

Human blood eosinophils exhibit a hyperactive phenotype in response to chemotactic factors after cell "priming" with IL-5 family cytokines. Earlier work has identified ERK1/2 as molecular markers for IL-5 priming, and in this article, we show that IL-3, a member of the IL-5 family, also augments fMLP-stimulated ERK1/2 phosphorylation in primary eosinophils. Besides ERK1/2, we also observed an enhancement of chemotactic factor-induced Akt phosphorylation after IL-5 priming of human blood eosinophils. Administration of a peptide antagonist that targets the Src family member Lyn before cytokine (IL-5/IL-3) priming of blood eosinophils inhibited the synergistic increase of fMLP-induced activation of Ras, ERK1/2 and Akt, as well as the release of the proinflammatory factor leukotriene C(4). In this study, we also examined a human eosinophil-like cell line HL-60 clone-15 and observed that these cells exhibited significant surface expression of IL-3Rs and GM-CSFRs, as well as ERK1/2 phosphorylation in response to the addition of IL-5 family cytokines or the chemotactic factors fMLP, CCL5, and CCL11. Consistent with the surface profile of IL-5 family receptors, HL-60 clone-15 recapitulated the enhanced fMLP-induced ERK1/2 phosphorylation observed in primary blood eosinophils after priming with IL-3/GM-CSF, and small interfering RNA-mediated knockdown of Lyn expression completely abolished the synergistic effects of IL-3 priming on fMLP-induced ERK1/2 phosphorylation. Altogether, our data demonstrate a central role for Lyn in the mechanisms of IL-5 family priming and suggest that Lyn contributes to the upregulation of the Ras-ERK1/2 and PI3K-Akt cascades, as well as the increased leukotriene C(4) release observed in response to fMLP in "primed" eosinophils.

IL-3 controls tau modifications and protects cortical neurons from neurodegeneration.

Interleukin-3 (IL-3) regulates the proliferation, survival and differentiation of haematopoietic cells via interaction with specific cell-surface receptors. IL-3 is expressed in several non-hematopoietic cell types. Studies have demonstrated the presence of IL-3 in the central nervous system, however, its physiological role in these cells is poorly understood. Previously we have been demonstrated that IL-3 prevents neuronal death induced by fibrillary ß amyloid in these cells, by PI 3-kinase and Jak/STAT pathway activation. In this study, we demonstrated that IL-3 significantly reduced Aß-promoted neurite degeneration and toxicity. Thus, this cytokine provides cellular protection against Aß neurotoxicity in primary cortical neuronal cells, by modulating microtubular dynamics and prevention of tau cleavage and hyperphosphorylation. We also demonstrates that IL-3 is expressed in the "in vivo" mouse model of AD, Tg2576, which also expresses human AßPP with the Swedish mutation. In summary, these results suggest that IL-3 could play a neuroprotective role in AD.

The roles of BMP and IL-3 signaling pathways in the control of hematopoietic stem cells in the mouse embryo.

During mouse ontogeny, the first adult-type hematopoietic stem cells (HSC) are autonomously generated at mid-gestation in the AGM (Aorta-Gonad-Mesonephros) region. Successively present in different anatomical sites where they will expand, HSCs will finally colonize the bone marrow (BM) where they will reside during the entire adult life. In the bone marrow, both HSC self-renewal and differentiation are controlled at cellular and molecular levels by interactions with the stromal microenvironment. So far, very little is known about the extracellular factors involved in the regulation of embryonic HSC emergence, survival and expansion. In the present review, we outline the BMP and IL-3 signaling pathways that are critical for the growth and potential of embryonic HSCs. We will also discuss how these pathways might be integrated with the ones of Notch and Mpl/thrombopoietin, also identified as important key regulators of AGM HSC activity.

Mice that "conditionally" lack basophils, AT LAST.

Basophils are the least abundant granulocytes found in the circulation. Until recently, their functions were poorly understood. In the past few years, the list of basophil functions in the context of immunity has dramatically increased. Thus, the need for basophil-deficient animal models to confirm these findings is imperative. In this issue of the JCI, Wada and colleagues introduce the first mouse model in which basophils are conditionally ablated in vivo. Using this model, they then uncover a nonredundant role for basophils in acquired immunity against tick infection.