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Group 2 innate lymphoid cells (ILC2s) in the lung are stimulated by inhaled allergens. ILC2s do not directly recognize allergens but they are stimulated by cytokines including interleukin (IL)-33 released by damaged epithelium. In response to allergens,lung ILC2s produce T helper 2 cell type cytokines inducing T cell-independent allergic lung inflammation. Here we examined the fate of lung ILC2s upon allergen challenges. ILC2s proliferated and secreted cytokines upon initial stimulation with allergen or IL-33,and this phase was followed by a contraction phase as cytokine production ceased. Some ILC2s persisted long after the resolution of the inflammation as allergen-experienced ILC2s and responded to unrelated allergens more potently than naive ILC2s,mediating severe allergic inflammation. The allergen-experienced ILC2s exhibited a gene expression profile similar to that of memory T cells. The memory-like properties of allergen-experienced ILC2s may explain why asthma patients are often sensitized to multiple allergens. View Publication

West Nile virus (WNV) infection is a mosquito-borne zoonosis with increasing prevalence in the United States. WNV infection begins in the skin,and the virus replicates initially in keratinocytes and dendritic cells (DCs). In the skin and cutaneous lymph nodes,infected DCs are likely to interact with invariant natural killer T cells (iNKTs). Bidirectional interactions between DCs and iNKTs amplify the innate immune response to viral infections,thus controlling viral load and regulating adaptive immunity. iNKTs are stimulated by CD1d-bound lipid antigens or activated indirectly by inflammatory cytokines. We exposed human monocyte-derived DCs to WNV Kunjin and determined their ability to activate isolated blood iNKTs. DCs became infected as judged by synthesis of viral mRNA and Envelope and NS-1 proteins,but did not undergo significant apoptosis. Infected DCs up-regulated the co-stimulatory molecules CD86 and CD40,but showed decreased expression of CD1d. WNV infection induced DC secretion of type I interferon (IFN),but no or minimal interleukin (IL)-12,IL-23,IL-18 or IL-10. Unexpectedly,we found that the WNV-infected DCs stimulated human iNKTs to up-regulate CD69 and produce low amounts of IL-10,but not proinflammatory cytokines such as IFN-γ or tumour necrosis factor (TNF)-α. Both CD1d and IFNAR blockade partially abrogated this iNKT response,suggesting involvement of a T cell receptor (TCR)-CD1d interaction and type I interferon receptor (IFNAR) signalling. Thus,WNV infection interferes with DC-iNKT interactions by preventing the production of proinflammatory cytokines. iNKTs may be a source of IL-10 observed in human flavivirus infections and initiate an anti-inflammatory innate response that limits adaptive immunity and immune pathology upon WNV infection. View Publication

A critical component of innate immune response to infection and tissue damage is the NACHT,LRR,and PYD domains-containing protein 3 (NLRP3) inflammasome,and this pathway and its activation products have been implicated in the pathophysiology of a variety of diseases. NLRP3 inflammasome activation leads to the cleavage of pro-IL-1β and pro-IL-18,as well as the subsequent release of biologically active IL-1β,IL-18,and other soluble mediators of inflammation. In this study,we further define the pharmacology of the previously reported NLRP3 inflammasome-selective,IL-1β processing inhibitor CP-456,773 (also known as MCC950),and we demonstrate its efficacy in two in vivo models of inflammation. Specifically,we show that in human and mouse innate immune cells CP-456,773 is an inhibitor of the cellular release of IL-1β,IL-1α,and IL-18,that CP-456,773 prevents inflammasome activation induced by disease-relevant soluble and crystalline NLRP3 stimuli,and that CP-456,773 inhibits R848- and imiquimod-induced IL-1β release. In mice,CP-456,773 demonstrates potent inhibition of the release of proinflammatory cytokines following acute i.p. challenge with LPS plus ATP in a manner that is proportional to the free/unbound concentrations of the drug,thereby establishing an in vivo pharmacokinetic/pharmacodynamic model for CP-456,773. Furthermore,CP-456,773 reduces ear swelling in an imiquimod cream-induced mouse model of skin inflammation,and it reduces airway inflammation in mice following acute challenge with house dust mite extract. These data implicate the NLRP3 inflammasome in the pathogenesis of dermal and airway inflammation,and they highlight the utility of CP-456,773 for interrogating the contribution of the NLRP3 inflammasome and its outputs in preclinical models of inflammation and disease. View Publication

Understanding how memory B cells are induced and relate to long-lived plasma cells is important for vaccine development. Immunity to oral vaccines has been considered short-lived because of a poor ability to develop IgA B-cell memory. Here we demonstrate that long-lived mucosal IgA memory is readily achieved by oral but not systemic immunization in mouse models with NP hapten conjugated with cholera toxin and transfer of B1-8(high)/GFP(+) NP-specific B cells. Unexpectedly,memory B cells are poorly related to long-lived plasma cells and less affinity-matured. They are α4β7-integrin(+)CD73(+)PD-L2(+)CD80(+) and at systemic sites mostly IgM(+),while 80% are IgA(+) in Peyer's patches. On reactivation,most memory B cells in Peyer's patches are GL7(-),but expand in germinal centres and acquire higher affinity and more mutations,demonstrating strong clonal selection. CCR9 expression is found only in Peyer's patches and appears critical for gut homing. Thus,gut mucosal memory possesses unique features not seen after systemic immunization. View Publication

The design of immunogens that elicit broadly reactive neutralizing antibodies (bnAbs) has been a major obstacle to HIV-1 vaccine development. One approach to assess potential immunogens is to use mice expressing precursors of human bnAbs as vaccination models. The bnAbs of the VRC01-class derive from the IGHV1-2 immunoglobulin heavy chain and neutralize a wide spectrum of HIV-1 strains via targeting the CD4 binding site of the envelope glycoprotein gp120. We now describe a mouse vaccination model that allows a germline human IGHV1-2(∗)02 segment to undergo normal V(D)J recombination and,thereby,leads to the generation of peripheral B cells that express a highly diverse repertoire of VRC01-related receptors. When sequentially immunized with modified gp120 glycoproteins designed to engage VRC01 germline and intermediate antibodies,IGHV1-2(∗)02-rearranging mice,which also express a VRC01-antibody precursor light chain,can support the affinity maturation of VRC01 precursor antibodies into HIV-neutralizing antibody lineages. View Publication

Natural killer (NK) cells form an important arm of the innate immune system and function to combat a wide range of invading pathogens,ranging from viruses to bacteria. However,the means by which NK cells accomplish recognition of pathogens with a limited repertoire of receptors remain largely unknown. In the current study,we describe the recognition of an emerging fungal pathogen,Candida glabrata,by the human NK cytotoxic receptor NKp46 and its mouse ortholog,NCR1. Using NCR1 knockout mice,we observed that this receptor-mediated recognition was crucial for controlling C. glabrata infection in vitro and in vivo. Finally,we delineated the fungal ligands to be the C. glabrata adhesins Epa1,Epa6,and Epa7 and demonstrated that clearance of systemic C. glabrata infections in vivo depends on their recognition by NCR1. As NKp46 and NCR1 have been previously shown to bind viral adhesion receptors,we speculate that NKp46/NCR1 may be a novel type of pattern recognition receptor. View Publication

Class switch recombination (CSR) in B cells requires the timely repair of DNA double-stranded breaks (DSBs) that result from lesions produced by activation-induced cytidine deaminase (AID). Through a genome-wide RNAi screen,we identified Kin17 as a gene potentially involved in the maintenance of CSR in murine B cells. In this study,we confirm a critical role for Kin17 in CSR independent of AID activity. Furthermore,we make evident that DSBs generated by AID or ionizing radiation require Kin17 for efficient repair and resolution. Our report shows that reduced Kin17 results in an elevated deletion frequency following AID mutational activity in the switch region. In addition,deficiency in Kin17 affects the functionality of multiple DSB repair pathways,namely homologous recombination,non-homologous end-joining,and alternative end-joining. This report demonstrates the importance of Kin17 as a critical factor that acts prior to the repair phase of DSB repair and is of bona fide importance for CSR. View Publication

The host responds to virus infection by activating type I interferon (IFN) signaling leading to expression of IFN-stimulated genes (ISGs). Dysregulation of the IFN response results in inflammatory diseases and chronic infections. In this study,we demonstrate that IFN regulatory factor 2 (IRF2),an ISG and a negative regulator of IFN signaling,influences alphavirus neuroinvasion and pathogenesis. A Sindbis virus strain that in wild-type (WT) mice only causes disease when injected into the brain leads to lethal encephalitis in Irf2(-/-) mice after peripheral inoculation. Irf2(-/-) mice fail to control virus replication and recruit immune infiltrates into the brain. Reduced B cells and virus-specific IgG are observed in the Irf2(-/-) mouse brains despite the presence of peripheral neutralizing antibodies,suggesting a defect in B cell trafficking to the central nervous system (CNS). B cell-deficient μMT mice are significantly more susceptible to viral infection,yet WT B cells and serum are unable to rescue the Irf2(-/-) mice. Collectively,our data demonstrate that proper localization of B cells and local production of antibodies in the CNS are required for protection. The work advances our understanding of host mechanisms that affect viral neuroinvasion and their contribution to immunity against CNS infections. View Publication

The developmental pathway for human megakaryocytes remains unclear and the definition of pure unipotent megakaryocyte progenitor is still controversial. Using single-cell transcriptome analysis,we have identified a cluster of cells within immature hematopoietic stem and progenitor cell populations that specifically express genes related to the megakaryocyte lineage. We used CD41 as a positive marker to identify these cells within the CD34(+)CD38(+)IL-3Rα(dim)CD45RA(-) common myeloid progenitor (CMP) population. These cells lacked erythroid and granulocyte/macrophage potential,but exhibited robust differentiation into the megakaryocyte lineage at a high frequency,both in vivo and in vitro The efficiency and expansion potential of these cells exceeded those of conventional bipotent megakaryocyte/erythrocyte progenitors. Accordingly,the CD41(+) CMP was defined as a unipotent megakaryocyte progenitor (MegP) that is likely to represent the major pathway for human megakaryopoiesis,independent of canonical megakaryocyte-erythroid lineage bifurcation. In the bone marrow of patients with essential thrombocythemia,the MegP population was significantly expanded in the context of a high burden of Janus kinase 2 mutations. Thus,the prospectively isolatable and functionally homogeneous human MegP will be useful for the elucidation of the mechanisms underlying normal and malignant human hematopoiesis. View Publication

The high risk of neonatal death from sepsis is thought to result from impaired responses by innate immune cells; however,the clinical observation of hyperinflammatory courses of neonatal sepsis contradicts this concept. Using transcriptomic,epigenetic and immunological approaches,we demonstrated that high amounts of the perinatal alarmins S100A8 and S100A9 specifically altered MyD88-dependent proinflammatory gene programs. S100 programming prevented hyperinflammatory responses without impairing pathogen defense. TRIF-adaptor-dependent regulatory genes remained unaffected by perinatal S100 programming and responded strongly to lipopolysaccharide,but were barely expressed. Steady-state expression of TRIF-dependent genes increased only gradually during the first year of life in human neonates,shifting immune regulation toward the adult phenotype. Disruption of this critical sequence of transient alarmin programming and subsequent reprogramming of regulatory pathways increased the risk of hyperinflammation and sepsis. Collectively these data suggest that neonates are characterized by a selective,transient microbial unresponsiveness that prevents harmful hyperinflammation in the delicate neonate while allowing for sufficient immunological protection. View Publication

OBJECTIVE: To explore the effects of anti-CD44 monoclonal antibody-IM7 on the in vitro adhesion and migration of chronic myeloid leukemia stem cell (CML-LSC) and its mechanism. METHODS: CD34(+)CD38(-)CD123(+) leukemic stem cells (LSC) from 20 newly-diagnosed chronic myeloid leukemia (CML) patients BM cells and CD34(+)CD38(-) hematopoietic stem cells (HSC) from 20 full-term newborn cord blood cells were isolated with EasySep(TM) magnet beads. The CD44 expression of the LSC and HSC was detected by flow cytometry (FCM),and the adhesion and migration ability of the LSC and HSC pre- and post-incubated with IM7 in vitro by MTT assay and transendothelial migration assay,respectively. RESULTS: (1) After incubated with IM7,the LSC and HSC CD44 expression rates were (86.60 ± 2.10)% vs. (25.40 ± 1.70)% (P textless 0.05),respectively. (2) The adhesive ability of the LSC to endothelial cells was decreased markedly after incubated with IM7,the OD value (A(570)) changing from pre-incubation of (0.62 ± 0.11) to post-incubation of (0.34 ± 0.07),while there was little change of A(570) in the HSC group. (3) The migration ability of the LSC group was inhibited evidently after incubated with IM7,the inhibition rate being 46% ∼ 63%,while little change of that in HSC group was detected. (4) The adhesive ability of the LSC group to marrow stromal cells was decreased markedly after incubated with IM7,while little change was found in that of HSC group. CONCLUSION: The anti-CD44 monoclonal antibody-IM7 can effectively inhibit the adhesion and migration abilities of the LSC in vitro,which might provide a theoretical evidence for targeting therapy. View Publication

Retinoic acid (RA) imprints gut-homing specificity on T cells upon activation by inducing the expression of chemokine receptor CCR9 and integrin α4β7. CCR9 expression seemed to be more highly dependent on RA than was the α4β7 expression,but its molecular mechanism remained unclear. In this article,we show that NFAT isoforms NFATc1 and NFATc2 directly interact with RA receptor (RAR) and retinoid X receptor (RXR) but play differential roles in RA-induced CCR9 expression on murine naive CD4(+) T cells. TCR stimulation for 6-24 h was required for the acquisition of responsiveness to RA and induced activation of NFATc1 and NFATc2. However,RA failed to induce CCR9 expression as long as TCR stimulation continued. After terminating TCR stimulation or adding cyclosporin A to the culture,Ccr9 gene transcription was induced,accompanied by inactivation of NFATc1 and sustained activation of NFATc2. Reporter and DNA-affinity precipitation assays demonstrated that the binding of NFATc2 to two NFAT-binding sites and that of the RAR/RXR complex to an RA response element half-site in the 5'-flanking region of the mouse Ccr9 gene were critical for RA-induced promoter activity. NFATc2 directly bound to RARα and RXRα,and it enhanced the binding of RARα to the RA response element half-site. NFATc1 also bound to the NFAT-binding sites and directly to RARα and RXRα,but it inhibited the NFATc2-dependent promoter activity. These results suggest that the cooperativity between NFATc2 and the RAR/RXR complex is essential for CCR9 expression on T cells and that NFATc1 interferes with the action of NFATc2. View Publication