Clostridioides difficile toxin B subverts germinal center and antibody recall responses by stimulating a drug-treatable CXCR4-dependent mechanism.

Recurrent Clostridioides difficile infection (CDI) results in significant morbidity and mortality. We previously established that CDI in mice does not protect against reinfection and is associated with poor pathogen-specific B cell memory (Bmem), recapitulating our observations with human Bmem. Here, we demonstrate that the secreted toxin TcdB2 is responsible for subversion of Bmem responses. TcdB2 from an endemic C. difficile strain delayed immunoglobulin G (IgG) class switch following vaccination, attenuated IgG recall to a vaccine booster, and prevented germinal center formation. The mechanism of TcdB2 action included increased B cell CXCR4 expression and responsiveness to its ligand CXCL12, accounting for altered cell migration and a failure of germinal center-dependent Bmem. These results were reproduced in a C. difficile infection model, and a US Food and Drug Administration (FDA)-approved CXCR4-blocking drug rescued germinal center formation. We therefore provide mechanistic insights into C. difficile-associated pathogenesis and illuminate a target for clinical intervention to limit recurrent disease.

The nanobody targeting PD-L1 and CXCR4 counteracts pancreatic stellate cell-mediated tumour progression by disrupting tumour microenvironment.

Pancreatic ductal adenocarcinoma (PDAC) is the most lethal malignancy worldwide owing to its complex tumour microenvironment and dense physical barriers. Stromal-derived factor-1 (SDF-1), which is abundantly secreted by tumour stromal cells, plays a pivotal role in promoting PDAC growth and metastasis. In this study, we investigated the impact and molecular mechanisms of the anti-PD-L1&CXCR4 bispecific nanobody on the TME and their consequent interference with PDAC progression. We found that blocking the SDF-1/CXCR4 signalling pathway delayed the epithelial-mesenchymal transition in pancreatic cancer cells. Anti-PD-L1&CXCR4 bispecific nanobody effectively suppress the secretion of SDF-1 by pancreatic stellate cells and downregulate the expression of smooth muscle actin alpha(α-SMA), thereby preventing the activation of cancer-associated fibroblasts by downregulating the PI3K/AKT signaling pathway. This improves the pancreatic tumour microenvironment, favouring the infiltration of T cells into the tumour tissue. In conclusion, our results suggest that the anti-PD-L1&CXCR4 bispecific nanobody exerts an antitumor immune response by changing the pancreatic tumour microenvironment. Hence, the anti-PD-L1&CXCR4 bispecific nanobody is a potential candidate for pancreatic cancer treatment.

Molecular profile reveals immune-associated markers of medulloblastoma for different subtypes.

Medulloblastoma, a common pediatric malignant tumor, has been recognized to have four molecular subgroups [wingless (WNT), sonic hedgehog (SHH), group 3, group 4], which are defined by the characteristic gene transcriptomic and DNA methylomic profiles, and has distinct clinical features within each subgroup. The tumor immune microenvironment is integral in tumor initiation and progression and might be associated with therapeutic responses. However, to date, the immune infiltrative landscape of medulloblastoma has not yet been elucidated. Thus, we proposed MethylCIBERSORT to estimate the degree of immune cell infiltration and weighted correlation network analysis (WGCNA) to find modules of highly correlated genes. Synthesizing the hub genes in the protein-protein interaction (PPI) network and modules of the co-expression network, we identify three candidate biomarkers [GRB2-associated-binding protein 1 (GAB1), Abelson 1 (ABL1), and CXC motif chemokine receptor type 4 (CXCR4)] via the molecular profiles of medulloblastoma. Given this, we investigated the correlation between these three immune hub genes and immune checkpoint blockade response and the potential of drug prediction further. In addition, this study demonstrated a higher presence of endothelial cells and infiltrating immune cells in Group 3 tumor bulk. The above results will be conducive to better comprehending the immune-related pathogenesis and treatment of medulloblastoma.

Decidual CXCR4+ CD56bright NK cells as a novel NK subset in maternal-foetal immune tolerance to alleviate early pregnancy failure.

Natural killer (NK) cells preferentially accumulate at maternal-foetal interface and are believed to play vital immune-modulatory roles during early pregnancy and related immunological dysfunction may result in pregnant failure such as recurrent miscarriage (RM). However, the mechanisms underlying the establishment of maternal-foetal immunotolerance are complex but clarifying the roles of decidual NK (dNK) cells offers the potential to design immunotherapeutic strategies to assist RM patients. In this report, we analysed RNA sequencing on peripheral NK (pNK) and decidual NK cells during early pregnancy; we identified an immunomodulatory dNK subset CXCR4+ CD56bright dNK and investigated its origin and phenotypic and functional characteristics. CXCR4+ CD56bright dNK displayed a less activated and cytotoxic phenotype but an enhanced immunomodulatory potential relative to the CXCR4 negative subset. CXCR4+ CD56bright dNK promote Th2 shift in an IL-4-dependent manner and can be recruited from peripheral blood and reprogramed by trophoblasts, as an active participant in the establishment of immune-tolerance during early pregnancy. Diminished CXCR4+ dNK cells and their impaired ability to induce Th2 differentiation were found in RM patients and mouse models of spontaneous abortion. Moreover, adoptive transfer of CXCR4+ dNK cells to NK-deficient (Nfil3-/-) mice showed great therapeutic potential of CXCR4+ dNK via recovering the Th2/Th1 bias and reducing embryo resorption rates. The identification of this new dNK cell subset may lay the foundation for understanding NK cell mechanisms in early pregnancy and provide potential prognostic factors for the diagnosis and therapy of RM.

Co-receptor signaling in the pathogenesis of neuroHIV.

The HIV co-receptors, CCR5 and CXCR4, are necessary for HIV entry into target cells, interacting with the HIV envelope protein, gp120, to initiate several signaling cascades thought to be important to the entry process. Co-receptor signaling may also promote the development of neuroHIV by contributing to both persistent neuroinflammation and indirect neurotoxicity. But despite the critical importance of CXCR4 and CCR5 signaling to HIV pathogenesis, there is only one therapeutic (the CCR5 inhibitor Maraviroc) that targets these receptors. Moreover, our understanding of co-receptor signaling in the specific context of neuroHIV is relatively poor. Research into co-receptor signaling has largely stalled in the past decade, possibly owing to the complexity of the signaling cascades and functions mediated by these receptors. Examining the many signaling pathways triggered by co-receptor activation has been challenging due to the lack of specific molecular tools targeting many of the proteins involved in these pathways and the wide array of model systems used across these experiments. Studies examining the impact of co-receptor signaling on HIV neuropathogenesis often show activation of multiple overlapping pathways by similar stimuli, leading to contradictory data on the effects of co-receptor activation. To address this, we will broadly review HIV infection and neuropathogenesis, examine different co-receptor mediated signaling pathways and functions, then discuss the HIV mediated signaling and the differences between activation induced by HIV and cognate ligands. We will assess the specific effects of co-receptor activation on neuropathogenesis, focusing on neuroinflammation. We will also explore how the use of substances of abuse, which are highly prevalent in people living with HIV, can exacerbate the neuropathogenic effects of co-receptor signaling. Finally, we will discuss the current state of therapeutics targeting co-receptors, highlighting challenges the field has faced and areas in which research into co-receptor signaling would yield the most therapeutic benefit in the context of HIV infection. This discussion will provide a comprehensive overview of what is known and what remains to be explored in regard to co-receptor signaling and HIV infection, and will emphasize the potential value of HIV co-receptors as a target for future therapeutic development.

CD101 genetic variants modify regulatory and conventional T cell phenotypes and functions.

We recently reported that the risk of sexually acquired HIV-1 infection is increased significantly by variants in the gene encoding CD101, a protein thought to modify inflammatory responses. Using blood samples from individuals with and without these variants, we demonstrate that CD101 variants modify the prevalence of circulating inflammatory cell types and show that CD101 variants are associated with increased proinflammatory cytokine production by circulating T cells. One category of CD101 variants is associated with a reduced capacity of regulatory T cells to suppress T cell cytokine production, resulting in a reduction in the baseline level of immune quiescence. These data are supported by transcriptomics data revealing alterations in the intrinsic regulation of antiviral pathways and HIV resistance genes in individuals with CD101 variants. Our data support the hypothesis that CD101 contributes to homeostatic regulation of bystander inflammation, with CD101 variants altering heterosexual HIV-1 acquisition by facilitating increased prevalence and altered function of T cell subsets.

The ERß-CXCL19/CXCR4-NFκB pathway is critical in mediating the E2-induced inflammation response in the orange-spotted grouper (Epinephelus coioides).

The main physiological function of 17ß-estradiol (E2) in vertebrates is to regulate sexual development and reproduction. In fish, especially hermaphroditic fish, estrogen is often used to aid reproduction, but it also can trigger an inflammatory response. However, the molecular mechanism for this E2-induced inflammatory reaction is not clear. In this study, we found that the ERß-CXCL19/CXCR4-NFκB cascade regulated the E2-induced inflammatory response in the orange-spotted grouper (Epinephelus coioides). Strikingly, E2 treatment resulted in significantly high expression of inflammatory cytokines and induced phosphorylation and degradation of IκBα and translocation of NFκB subunit p65 to the nucleus in grouper spleen cells. However, the E2-induced inflammatory response could be prevented by the broad estrogen receptor (ER) ligand ICI 182,780. Moreover, the luciferase assay showed that E2 induced the inflammatory response by activating the promotor of chemokine CXCL19 through ERß1 and ERß2. Knockdown of CXCL19 blocked the E2-induced inflammatory response and NFκB nucleus translocation. Additionally, knockdown of chemokines CXCR4a and CXCR4b together, but not alone, blocked the E2-induced inflammatory response. The immunofluorescence assay and co-immunoprecipitation analysis showed that CXCL19 mediated the E2-induced inflammatory response by activating CXCR4a or CXCR4b. Taken together, these results showed that the ERß-CXCL19/CXCR4-NFκB pathway mediated the E2-induced inflammatory response in grouper. These findings are valuable for future comparative immunological studies and provide a theoretical basis for mitigating the adverse reactions that occur when using E2 to help fish reproduce.

Expression of chemokine receptor CXCR4 in tumor cells and content of CXCL12+-fibroblasts in endometrioid carcinoma of endometrium.

BACKGROUND: The expression of the CXCL12 chemokine and its receptor CXCR4 in the stromal component of the tumor plays an important role in tumor cell migration, proliferation, inhibition of apoptosis and determination of invasive and metastatic potential of malignant neoplasms of various genesis. The significance of CXCL12 and CXCR4 expression in endometrial tumor cells for cancer progression is not fully understood. AIM: To evaluate the content of CXCL12+-fibroblasts and expression of CXCL12 and CXCR4 in endometrial cancer cells, depending on the tumor stage. MATERIALS AND METHODS: Surgical material of 45 patients with endometrioid carcinoma of the endometrium (ECE) of the stages I-II and III was studied using morphological and immunohistochemical methods. RESULTS: In ECE of stage I-II CXCR4 expression was lower (43.3 ± 4.2%) while CXCL12 expression was higher (33.6 ± 2.4%) compared with the corresponding indices​​ in ECE of stage III (63.6 ± 3.5%, 24.5 ± 1.9%, respectively, p < 0.05). In ECE of stage III, high expression of CXCR4 (> Me) and low CXCL12 (< Me) was observed in 80% of samples; these tumors invaded more than 1/2 of the myometrium. There was a positive correlation between the depth of tumor invasion in the myometrium and the presence of metastases and CXCR4 expression in tumor cells (R = 0.5 and R = 0.4, respectively, p < 0.05) and the negative correlation with the expression of CXCL12 (R = -0.6 and R = -0.3, respectively, p < 0.05). In tumors that deeply invaded the myometrium, a high number of the CXCL12+-fibroblasts (> Me) (14.9 ± 1.3%) was detected. CONCLUSION: The obtained data reflect the communication of the immunosuppressive factor of the tumor microenvironment, i.e. CXCL12+-fibroblasts and CXCR4 expressing tumor cells. We suggest that the aggressiveness of ECE is determined by the combined effect of these two factors.

Single-cell dissection of cellular components and interactions shaping the tumor immune phenotypes in ovarian cancer.

Distinct T cell infiltration patterns, i.e., immune infiltrated, excluded, and desert, result in different responses to cancer immunotherapies. However, the key determinants and biology underpinning these tumor immune phenotypes remain elusive. Here, we provide a high-resolution dissection of the entire tumor ecosystem through single-cell RNA-sequencing analysis of 15 ovarian tumors. Immune-desert tumors are characterized by unique tumor cell-intrinsic features, including metabolic pathways and low antigen presentation, and an enrichment of monocytes and immature macrophages. Immune-infiltrated and -excluded tumors differ markedly in their T cell composition and fibroblast subsets. Furthermore, our study reveals chemokine receptor-ligand interactions within and across compartments as potential mechanisms mediating immune cell infiltration, exemplified by the tumor cell-T cell cross talk via CXCL16-CXCR6 and stromal-immune cell cross talk via CXCL12/14-CXCR4. Our data highlight potential molecular mechanisms that shape the tumor immune phenotypes and may inform therapeutic strategies to improve clinical benefit from cancer immunotherapies.

Development of an Antigen-Antibody Co-Display System for Detecting Interaction of G-Protein-Coupled Receptors and Single-Chain Variable Fragments.

G-protein-coupled receptors (GPCRs), especially chemokine receptors, are ideal targets for monoclonal antibody drugs. Considering the special multi-pass transmembrane structure of GPCR, it is often a laborious job to obtain antibody information about off-targets and epitopes on antigens. To accelerate the process, a rapid and simple method needs to be developed. The split-ubiquitin-based yeast two hybrid system (YTH) was used as a blue script for a new method. By fusing with transmembrane peptides, scFv antibodies were designed to be anchored on the cytomembrane, where the GPCR was co-displayed as well. The coupled split-ubiquitin system transformed the scFv-GPCR interaction signal into the expression of reporter genes. By optimizing the topological structure of scFv fusion protein and key elements, including signal peptides, transmembrane peptides, and flexible linkers, a system named Antigen-Antibody Co-Display (AACD) was established, which rapidly detected the interactions between antibodies and their target GPCRs, CXCR4 and CXCR5, while also determining the off-target antibodies and antibody-associated epitopes. The AACD system can rapidly determine the association between GPCRs and their candidate antibodies and shorten the research period for off-target detection and epitope identification. This system should improve the process of GPCR antibody development and provide a new strategy for GPCRs antibody screening.

CXCL12-CXCR4-Mediated Chemotaxis Supports Accumulation of Mucosal-Associated Invariant T Cells Into the Liver of Patients With PBC.

Objectives: To explore the potential role of CD3+CD8+CD161high TCRVα7.2+ mucosal-associated invariant T (MAIT) cells in the pathogenesis of primary biliary cholangitis (PBC). Methods: We enrolled 55 patients with PBC, 69 healthy controls (HCs), and 8 patients with hepatic hemangioma. Circulating MAIT cells and their chemokine receptor profiles and cytokine production were quantified using flow cytometry. Liver-resident MAIT cells were examined by immunofluorescence staining. CXCL12-mediated chemotaxis of MAIT cells was measured using a transwell migration assay. Plasma interleukin (IL)-18 was measured using ELISA, and cytokine production in IL-18-stimulated MAIT cells was detected using flow cytometry. Result: Peripheral MAIT cells were found to be significantly lower in patients with PBC (3.0 ± 3.2% vs. 9.4 ± 8.0%, p < 0.01) and negatively correlated with alkaline phosphatase (ALP) levels (r = -0.3209, p < 0.05). Liver immunofluorescence staining suggested that MAIT cells might accumulate in PBC liver. MAIT cells from patients with PBC expressed higher levels of CXCR4 (84.8 ± 18.0% vs. 58.7 ± 11.4%, p < 0.01), and the expression of CXCL12 was higher in PBC liver. CXCL12 promoted MAIT cell chemotaxis (70.4 ± 6.8% vs. 52.2 ± 3.5%, p < 0.01), which was attenuated by CXCR4 antagonist. MAIT cells from PBC produced significantly more interferon-γ (IFN-γ) (88.3 ± 4.2% vs. 64.2 ± 10.1%, p < 0.01), tumor necrosis factor-α (TNF-α) (93.0 ± 1.1% vs. 80.1 ± 5.3%, p < 0.01), Granzyme B (89.3 ± 3.3% vs. 72.1 ± 7.0%, p < 0.01), and perforin (46.8 ± 6.6% vs. 34.8 ± 7.7%, p < 0.05). MAIT cells from PBC expressed higher levels of IL18-Rα (83.8 ± 10.2% vs. 58.3 ± 8.7%, p < 0.01). Plasma IL-18 was more abundant in patients with PBC (286.8 ± 75.7 pg/ml vs. 132.9 ± 78.1 pg/ml, p < 0.01). IL-18 promoted IFN-γ production in MAIT cells (74.9 ± 6.6% vs. 54.7 ± 6.7%, p < 0.01), which was partially attenuated by blocking IL-18R (68.6 ± 8.3% vs. 43.5 ± 4.2%, p < 0.01). Conclusion: Mucosal-associated invariant T cells from patients with PBC accumulated in the liver via CXCL12-CXCR4-mediated chemotaxis, produced pro-inflammatory cytokines, and contributed to portal inflammation, which was potentially mediated by elevated IL-18. Targeting MAIT cells might be a therapeutic approach for PBC.

Central human B cell tolerance manifests with a distinctive cell phenotype and is enforced via CXCR4 signaling in hu-mice.

Central B cell tolerance, the process restricting the development of many newly generated autoreactive B cells, has been intensely investigated in mouse cells while studies in humans have been hampered by the inability to phenotypically distinguish autoreactive and nonautoreactive immature B cell clones and the difficulty in accessing fresh human bone marrow samples. Using a human immune system mouse model in which all human Igκ+ B cells undergo central tolerance, we discovered that human autoreactive immature B cells exhibit a distinctive phenotype that includes lower activation of ERK and differential expression of CD69, CD81, CXCR4, and other glycoproteins. Human B cells exhibiting these characteristics were observed in fresh human bone marrow tissue biopsy specimens, although differences in marker expression were smaller than in the humanized mouse model. Furthermore, the expression of these markers was slightly altered in autoreactive B cells of humanized mice engrafted with some human immune systems genetically predisposed to autoimmunity. Finally, by treating mice and human immune system mice with a pharmacologic antagonist, we show that signaling by CXCR4 is necessary to prevent both human and mouse autoreactive B cell clones from egressing the bone marrow, indicating that CXCR4 functionally contributes to central B cell tolerance.

Mycobacterial infection-induced miR-206 inhibits protective neutrophil recruitment via the CXCL12/CXCR4 signalling axis.

Pathogenic mycobacteria actively dysregulate protective host immune signalling pathways during infection to drive the formation of permissive granuloma microenvironments. Dynamic regulation of host microRNA (miRNA) expression is a conserved feature of mycobacterial infections across host-pathogen pairings. Here we examine the role of miR-206 in the zebrafish model of Mycobacterium marinum infection, which allows investigation of the early stages of granuloma formation. We find miR-206 is upregulated following infection by pathogenic M. marinum and that antagomir-mediated knockdown of miR-206 is protective against infection. We observed striking upregulation of cxcl12a and cxcr4b in infected miR-206 knockdown zebrafish embryos and live imaging revealed enhanced recruitment of neutrophils to sites of infection. We used CRISPR/Cas9-mediated knockdown of cxcl12a and cxcr4b expression and AMD3100 inhibition of Cxcr4 to show that the enhanced neutrophil response and reduced bacterial burden caused by miR-206 knockdown was dependent on the Cxcl12/Cxcr4 signalling axis. Together, our data illustrate a pathway through which pathogenic mycobacteria induce host miR-206 expression to suppress Cxcl12/Cxcr4 signalling and prevent protective neutrophil recruitment to granulomas.

Pituitary adenylate cyclase-activating polypeptide promotes cutaneous dendritic cell functions in contact hypersensitivity.

BACKGROUND: Sensory nerves regulate cutaneous local inflammation indirectly through induction of pruritus and directly by acting on local immune cells. The underlying mechanisms for how sensory nerves influence cutaneous acquired immune responses remain to be clarified. OBJECTIVE: This study aimed to explore the effect of peripheral nerves on cutaneous immune cells in cutaneous acquired immune responses. METHODS: We analyzed contact hypersensitivity (CHS) responses as a murine model of delayed-type hypersensitivity in absence or presence of resiniferatoxin-induced sensory nerve denervation. We conducted ear thickness measurements, flow cytometric analyses, and mRNA expression analyses in CHS. RESULTS: CHS responses were attenuated in mice that were denervated during the sensitization phase of CHS. By screening neuropeptides, we found that pituitary adenylate cyclase-activating polypeptide (PACAP) mRNA expression was decreased in the dorsal root ganglia after denervation. Administration of PACAP restored attenuated CHS response in resiniferatoxin-treated mice, and pharmacological inhibition of PACAP suppressed CHS. Flow cytometric analysis of skin-draining lymph nodes showed that cutaneous dendritic cell migration and maturation were reduced in both denervated mice and PACAP antagonist-treated mice. The expression of chemokine receptors CCR7 and CXCR4 of dendritic cell s was enhanced by addition of PACAP in vitro. CONCLUSION: These findings indicate that a neuropeptide PACAP promotes the development of CHS responses by inducing cutaneous dendritic cell functions during the sensitization phase.

Platelets Independently Recruit into Asthmatic Lungs and Models of Allergic Inflammation via CCR3.

Platelet activation and pulmonary recruitment occur in patients with asthma and in animal models of allergic asthma, in which leukocyte infiltration, airway remodeling, and hyperresponsiveness are suppressed by experimental platelet depletion. These observations suggest the importance of platelets to various characteristics of allergic disease, but the mechanisms of platelet migration and location are not understood. The aim of this study was to assess the mechanism of platelet recruitment to extravascular compartments of lungs from patients with asthma and after allergen challenge in mice sensitized to house dust mite (HDM) extract (contains the DerP1 [Dermatophagoides pteronyssinus extract peptidase 1] allergen); in addition, we assessed the role of chemokines in this process. Lung sections were immunohistochemically stained for CD42b+ platelets. Intravital microscopy in allergic mice was used to visualize platelets tagged with an anti-mouse CD49b-PE (phycoerythrin) antibody. Platelet-endothelial interactions were measured in response to HDM (DerP1) exposure in the presence of antagonists to CCR3, CCR4, and CXCR4. Extravascular CD42b+ platelets were detected in the epithelium and submucosa in bronchial biopsy specimens taken from subjects with steroid-naive mild asthma. Platelets were significantly raised in the lung parenchyma from patients with fatal asthma compared with postmortem control-lung tissue. Furthermore, in DerP1-sensitized mice, subsequent HDM exposure induced endothelial rolling, endothelial adhesion, and recruitment of platelets into airway walls, compared with sham-sensitized mice, via a CCR3-dependent mechanism in the absence of aggregation or interactions with leukocytes. Localization of singular, nonaggregated platelets occurs in lungs of patients with asthma. In allergic mice, platelet recruitment occurs via recognized vascular adhesive and migratory events, independently of leukocytes via a CCR3-dependent mechanism.

Autoantibodies against C5aR1, C3aR1, CXCR3, and CXCR4 are decreased in primary Sjogren's syndrome.

BACKGROUND: Networks formed of numerous autoantibodies (aabs) directed against G-protein coupled receptors (GPCR) have been suggested to play important role in autoimmune disorders. In present study, we aimed to evaluate the association between anti-GPCR antibodies and primary Sjogren's syndrome (pSS) to determine the potential pathogenic factors. METHODS: By applying a cell membrane-based ELISA technique, which is capable of detecting aabs against conformational epitopes within GPCR, serum levels of fourteen GPCR were determined in well-characterized patients with pSS (n = 52) and gender-matched healthy controls (n = 54). Comparisons between groups were analyzed by two-tailed Mann-Whitney U test, Bonferroni correction was applied for multiple comparisons. Spearman`s rank correlation coefficients were calculated between variables and visualized by heat map. RESULTS: Compared to healthy subjects, sera of patients with pSS showed significantly higher binding to ß2AR and ETAR, but lower binding to C5aR1, C3aR1, CXCR3, and CXCR4. Autoantibodies against C5aR1, C3aR1, CXCR3, and CXCR4 were also decreased in patients with rheumatoid arthritis. In pSS patients, levels of anti-CXCR3 and anti-CXCR4 antibodies were negatively correlated with circulating lymphocyte counts. Furthermore, correlation signatures of anti-GPCR antibodies changed dramatically in the patients with pulmonary involvement. CONCLUSIONS: This study demonstrates an association between pSS and autoantibodies recognizing GPCR, especially those functionally involved in immune cell migration and exocrine glandular secretion.

Hematologic disorder-associated Cxcr4 gain-of-function mutation leads to uncontrolled extrafollicular immune response.

The extrafollicular immune response is essential to generate a rapid but transient wave of protective antibodies during infection. Despite its importance, the molecular mechanisms controlling this first response are poorly understood. Here, we demonstrate that enhanced Cxcr4 signaling caused by defective receptor desensitization leads to exacerbated extrafollicular B-cell response. Using a mouse model bearing a gain-of-function mutation of Cxcr4 described in 2 human hematologic disorders, warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome and Waldenström macroglobulinemia, we demonstrated that mutant B cells exhibited enhanced mechanistic target of rapamycin signaling, cycled more, and differentiated more potently into plasma cells than wild-type B cells after Toll-like receptor (TLR) stimulation. Moreover, Cxcr4 gain of function promoted enhanced homing and persistence of immature plasma cells in the bone marrow, a phenomenon recapitulated in WHIM syndrome patient samples. This translated in increased and more sustained production of antibodies after T-independent immunization in Cxcr4 mutant mice. Thus, our results establish that fine-tuning of Cxcr4 signaling is essential to limit the strength and length of the extrafollicular immune response.

Skin-resident natural killer T cells participate in cutaneous allergic inflammation in atopic dermatitis.

BACKGROUND: Natural killer T (NKT) cells are unconventional T cells that bridge innate and adaptive immunity. NKT cells have been implicated in the development of atopic dermatitis (AD). OBJECTIVE: We aimed to investigate the role of NKT cells in AD development, especially in skin. METHODS: Global proteomic and transcriptomic analyses were performed by using skin and blood from human healthy-controls and patients with AD. Levels of CXCR4 and CXCL12 expression in skin NKT cells were analyzed in human AD and mouse AD models. By using parabiosis and intravital imaging, the role of skin CXCR4+ NKT cells was further evaluated in models of mice with AD by using CXCR4-conditionally deficient or CXCL12 transgenic mice. RESULTS: CXCR4 and its cognate ligand CXCL12 were significantly upregulated in the skin of humans with AD by global transcriptomic and proteomic analyses. CXCR4+ NKT cells were enriched in AD skin, and their levels were consistently elevated in our models of mice with AD. Allergen-induced NKT cells participate in cutaneous allergic inflammation. Similar to tissue-resident memory T cells, the predominant skin NKT cells were CXCR4+ and CD69+. Skin-resident NKT cells uniquely expressed CXCR4, unlike NKT cells in the liver, spleen, and lymph nodes. Skin fibroblasts were the main source of CXCL12. CXCR4+ NKT cells preferentially trafficked to CXCL12-rich areas, forming an enriched CXCR4+ tissue-resident NKT cells/CXCL12+ cell cluster that developed in acute and chronic allergic inflammation in our models of mice with AD. CONCLUSIONS: CXCR4+ tissue-resident NKT cells may form a niche that contributes to AD, in which CXCL12 is highly expressed.

The association of Epstein-Barr virus infection with CXCR3+ B-cell development in multiple sclerosis: impact of immunotherapies.

Epstein-Barr virus (EBV) infection of B cells is associated with increased multiple sclerosis (MS) susceptibility. Recently, we found that CXCR3-expressing B cells preferentially infiltrate the CNS of MS patients. In chronic virus-infected mice, these types of B cells are sustained and show increased antiviral responsiveness. How EBV persistence in B cells influences their development remains unclear. First, we analyzed ex vivo B-cell subsets from MS patients who received autologous bone marrow transplantation (n = 9), which is often accompanied by EBV reactivation. The frequencies of nonclass-switched and class-switched memory B cells were reduced at 3-7 months, while only class-switched B cells returned back to baseline at 24-36 months posttransplantation. At these time points, EBV DNA load positively correlated to the frequency of CXCR3+ , and not CXCR4+ or CXCR5+ , class-switched B cells. Second, for CXCR3+ memory B cells trapped within the blood of MS patients treated with natalizumab (anti-VLA-4 antibody n = 15), latent EBV infection corresponded to enhanced in vitro formation of anti-EBNA1 IgG-secreting plasma cells under GC-like conditions. These findings imply that EBV persistence in B cells potentiates brain-homing and antibody-producing CXCR3+ subsets in MS.

Clinical Molecular Imaging of Pulmonary CXCR4 Expression to Predict Outcome of Pirfenidone Treatment in Idiopathic Pulmonary Fibrosis.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a progressive disease for which two antifibrotic drugs recently were approved. However, an unmet need exists to predict responses to antifibrotic treatment, such as pirfenidone. Recent data suggest that upregulated expression of CXCR4 is indicative of outcomes in IPF. RESEARCH QUESTION: Can quantitative, molecular imaging of pulmonary CXCR4 expression as a biomarker for disease activity predict response to the targeted treatment pirfenidone and prognosis in patients with IPF? STUDY DESIGN AND METHODS: CXCR4 expression was analyzed by immunohistochemistry examination of lung tissues and reverse-transcriptase polymerase chain reaction analysis of BAL. PET-CT scanning with the specific CXCR4 ligand 68Ga-pentixafor was performed in 28 IPF patients and compared with baseline clinical characteristics. In 16 patients, a follow-up scan was obtained 6 to 12 weeks after initiation of treatment with pirfenidone. Patients were followed up in our outpatient clinic for ≥ 12 months. RESULTS: Immunohistochemistry analysis showed high CXCR4 staining of epithelial cells and macrophages in areas with vast fibrotic remodeling. Targeted PET scanning revealed CXCR4 upregulation in fibrotic areas of the lungs, particularly in zones with subpleural honeycombing. Baseline CXCR4 signal demonstrated a significant correlation with Gender Age Physiology stage (r = 0.44; P = .02) and with high-resolution CT scan score (r = 0.38; P = .04). Early changes in CXCR4 signal after initiation of pirfenidone treatment correlated with the long-term course of FVC after 12 months (r = -0.75; P = .0008). Moreover, patients with a high pulmonary CXCR4 signal on follow-up PET scan after 6 weeks into treatment demonstrated a statistically significant worse outcome at 12 months (P = .002). In multiple regression analysis, pulmonary CXCR4 signal on follow-up PET scan emerged as the only independent predictor of long-term outcome (P = .0226). INTERPRETATION: CXCR4-targeted PET imaging identified disease activity and predicted outcome of IPF patients treated with pirfenidone. It may serve as a future biomarker for personalized guidance of antifibrotic treatment.