Moesin deficiency leads to lupus-like nephritis with accumulation of CXCL13-producing patrolling monocytes.

Moesin is a member of the ezrin-radixin-moesin (ERM) family of proteins that link plasma membrane proteins to the cortical cytoskeleton and thus regulate diverse cellular processes. Mutations in the human moesin gene cause a primary immunodeficiency called X-linked moesin-associated immunodeficiency (X-MAID), which may be complicated by an autoimmune phenotype with kidney involvement. We previously reported that moesin-deficient mice exhibit lymphopenia similar to that of X-MAID and develop a lupus-like autoimmune phenotype with age. However, the mechanism through which moesin defects cause kidney pathology remains obscure. Here, we characterized immune cell infiltration and chemokine expression in the kidney of moesin-deficient mice. We found accumulation of CD4+ T and CD11b+ myeloid cells and high expression of CXCL13, whose upregulation was detected before the onset of overt nephritis. CD4+ T cell population contained IFN-γ-producing effectors and expressed the CXCL13 receptor CXCR5. Among myeloid cells, Ly6Clo patrolling monocytes and MHCIIlo macrophages markedly accumulated in moesin-deficient kidneys and expressed high CXCL13 levels, implicating the CXCL13-CXCR5 axis in nephritis development. Functionally, Ly6Clo monocytes from moesin-deficient mice showed reduced migration toward sphingosine 1-phosphate. These findings suggest that moesin plays a role in regulating patrolling monocyte homeostasis, and that its defects lead to nephritis associated with accumulation of CXCL13-producing monocytes and macrophages.

Isolation of TCR genes with tumor-killing activity from tumor-infiltrating and circulating lymphocytes in a tumor rejection cynomolgus macaque model.

To develop effective adoptive cell transfer therapy using T cell receptor (TCR)-engineered T cells, it is critical to isolate tumor-reactive TCRs that have potent anti-tumor activity. In humans, tumor-infiltrating lymphocytes (TILs) have been reported to contain CD8+PD-1+ T cells that express tumor-reactive TCRs. Characterization of tumor reactivity of TILs from non-human primate tumors could improve anti-tumor activity of TCR-engineered T cells in preclinical research. In this study, we sought to isolate TCR genes from CD8+PD-1+ T cells among TILs in a cynomolgus macaque model of tumor transplantation in which the tumors were infiltrated with CD8+ T cells and were eventually rejected. We analyzed the repertoire of TCRα and ß pairs obtained from single CD8+PD-1+ T cells in TILs and circulating lymphocytes and identified multiple TCR pairs with high frequency, suggesting that T cells expressing these recurrent TCRs were clonally expanded in response to tumor cells. We further showed that the recurrent TCRs exhibited cytotoxic activity to tumor cells in vitro and potent anti-tumor activity in mice transplanted with tumor cells. These results imply that this tumor transplantation macaque model recapitulates key features of human TILs and can serve as a platform toward preclinical studies of non-human primate tumor models.

The ERM protein moesin regulates natural killer cell homeostasis in vivo.

Moesin is a member of the ezrin-radixin-moesin (ERM) family of proteins that link plasma membrane proteins with actin filaments in the cell cortex. Hemizygous mutations in the X-linked moesin gene are associated with primary immunodeficiency with T and B cell lymphopenia, which also affects natural killer (NK) cells in most cases. We previously showed that moesin deficiency in mice substantially affects lymphocyte homeostasis, but its impact on NK cells remains unexplored. Here, we found that in moesin-deficient mice, NK cells were decreased in the peripheral blood and bone marrow but increased in the spleen. Analysis of female heterozygous mice showed a selective advantage for moesin-expressing NK cells in the blood. Moesin-deficient NK cells exhibited increased cell death and impaired signaling in response to IL-15, suggesting that moesin regulates NK cell survival through IL-15-mediated signaling. Our findings thus identify moesin as an NK cell homeostasis regulator in vivo.

Alteration in endometrial helper T-cell subgroups in chronic endometritis.

PROBLEM: The effect of chronic endometritis (CE) on the subpopulation of CD4+ T cells, Th1, Th2, Th17, and regulatory T cells in the endometrium is unknown. METHOD OF STUDY: Lymphocytes were isolated from the endometrium of CE patients (n = 12) and non-CE patients (n = 7). The CD4+ T-cell profile was analyzed by flow cytometry and immunofluorescence. RESULTS: In the endometrium of CE patients, there were significantly more Th1 cells among CD4+ cells and fewer Th2 cells in comparison to non-CE patients. No marked difference was observed in Th17 cells or Foxp3+ Treg cells. Moreover, the proportion of Th1 cells increased and the proportion of Th2 cells decreased as the number of CD138+ cells increased. Furthermore, when the localization of CD138+ cells and CD4+ cells was examined, CD4+ cells were found to be clustered around CD138+ cells in CE patients. CONCLUSION: The CD4+ T-cell profile in the endometrium is altered in women with CE. This finding may help to clarify the pathophysiology and development of treatment methods for CE.

Characterization of tumour-infiltrating lymphocytes in a tumour rejection cynomolgus macaque model.

Immunotherapy has emerged as a promising and effective treatment for cancer, yet the clinical benefit is still variable, in part due to insufficient accumulation of immune effector cells in the tumour microenvironment. Better understanding of tumour-infiltrating lymphocytes (TILs) from nonhuman primate tumours could provide insights into improving effector cell accumulation in tumour tissues during immunotherapy. Here, we characterize TILs in a cynomolgus macaque tumour model in which the tumours were infiltrated with CD4+ and CD8+ T cells and were eventually rejected. The majority of CD4+ and CD8+ TILs exhibited a CD45RA-CCR7- effector memory phenotype, but unlike circulating T cells, they expressed CD69, a marker for tissue-resident memory T (TRM) cells. CD69-expressing CD8+ TILs expressed high levels of the cytotoxic molecule granzyme B and the co-inhibitory receptor PD-1. Consistent with the TRM cell phenotype, CD8+ TILs minimally expressed CX3CR1 but expressed CXCR3 at higher levels than circulating CD8+ T cells. Meanwhile, CXCL9, CXCL10 and CXCL11, chemokine ligands for CXCR3, were expressed at high levels in the tumours, thus attracting CXCR3+CD8+ T cells. These results indicate that tumour-transplanted macaques can be a useful preclinical model for studying and optimizing T cell accumulation in tumours for the development of new immunotherapies.

Citrullinated fibrinogen is a target of auto-antibodies in interstitial lung disease in mice with collagen-induced arthritis.

Interstitial lung disease (ILD) is a very common and lethal complication of rheumatoid arthritis (RA), yet its pathogenesis is not well understood, in part due to the lack of adequate animal models. Although collagen-induced arthritis (CIA) is the most widely used animal model for RA, the lung involvement occurring in this model has scarcely been studied. To evaluate the suitability of CIA as a model for RA-associated ILD (RA-ILD), we immunized DBA/1 mice with bovine type II collagen and characterized lung disease in this model. Histologic analyses revealed patchy interstitial infiltration of inflammatory cells in the peripheral regions of the lung, notably in the subpleural region, in mice with CIA. This pattern resembled usual interstitial pneumonia in humans, which is the most prevalent pattern in RA-ILD. Among infiltrates in the lung, CD11bhi macrophages of the M2 phenotype were most prominently increased. IgG and C3 were deposited in the subpleural region where inflammatory cells infiltrated. The sera from CIA mice contained auto-antibodies against citrullinated proteins, which are specific and predictive markers for RA. Protein citrullination was enhanced in the lung of CIA mice compared with naive mice, and citrullinated fibrinogen was primarily targeted by these auto-antibodies. The elevation of auto-antibodies against citrullinated proteins and their deposition in the lung with patchy subpleural preponderance suggest that CIA can serve as a model to study the pathogenesis of RA-ILD.

A novel Siglec-F+ neutrophil subset in the mouse nasal mucosa exhibits an activated phenotype and is increased in an allergic rhinitis model.

Neutrophils are important phagocytic cells for host defense against pathogens. They are rapidly recruited to the site of infection, release antimicrobial peptides and cytokines, and engulf and kill microbes. Neutrophils also accumulate in allergic inflammatory sites. Here we characterized neutrophil accumulation in the nasal mucosa using a mouse model of allergic rhinitis, in which mice were sensitized by intraperitoneal injection of ovalbumin (OVA) and then challenged by intranasal administration of OVA or PBS. In the nasal mucosa of both PBS- and OVA-challenged mice, we found a cell subset expressing the eosinophil marker Siglec-F in the Ly-6G+ neutrophil population. Morphological analysis of the sorted Ly-6G+Siglec-F+ cells revealed that they were devoid of eosinophilic granules in the cytosol and were apparently neutrophils, but compared to conventional Ly-6G+Siglec-F- neutrophils, they had a more lobulated, "botryoid" nucleus. Siglec-F+ neutrophils were barely found in the nasopharynx-associated lymphoid tissue, cervical lymph nodes, the spleen, or blood. Both Siglec-F+ neutrophils and conventional neutrophils showed increased numbers in the nasal mucosa of OVA-challenged mice. Compared to conventional Siglec-F- neutrophils, Siglec-F+ neutrophils exhibited an activated phenotype and enhanced effector functions. Taken together, our findings identify Siglec-F+ neutrophils as a novel neutrophil subset with an activated phenotype that resides specifically in the nasal mucosa.

CCL28-Deficient Mice Have Reduced IgA Antibody-Secreting Cells and an Altered Microbiota in the Colon.

CCL28 induces the migration of IgA Ab-secreting cells (ASCs) via CCR10 and also displays a potent antimicrobial activity in vitro. To explore the role of CCL28 in vivo, we generated CCL28-deficient mice. The mice exhibited a significant reduction and abnormal distribution of IgA ASCs in the lamina propria of the colon. The concentrations of total and Ag-specific IgA in the fecal extracts of CCL28-deficient mice were also drastically reduced. The average amount of IgA secreted by a single IgA ASC derived from the colon was also substantially reduced in CCL28-deficient mice. Furthermore, CCL28 was found to significantly increase the average amount of IgA secreted by a single IgA ASC derived from the colon in vitro. In contrast, the generation of IgA ASCs in Peyer's and cecal patches was not significantly impaired in CCL28-deficient mice. We also found a relative increase in the Class Bacilli in the fecal extracts of CCL28-deficient mice and demonstrated a potent antimicrobial activity of CCL28 against Bacillus cereus and Enterococcus faecalis, both of which belong to Class Bacilli. Thus, CCL28 may also suppress the outgrowth of some bacterial species by its direct antimicrobial activity. Finally, CCL28-deficient mice exhibited a highly aggravated dextran sodium sulfate-induced colitis that was ameliorated by pretreatment with antibiotics. Collectively, CCL28 plays a pivotal role in the homing, distribution, and function of IgA ASCs in the colon and may also affect the intestinal microbiota through its direct antimicrobial activity.

The ERM Protein Moesin Regulates CD8+ Regulatory T Cell Homeostasis and Self-Tolerance.

The ezrin-radixin-moesin (ERM) proteins are a family of membrane-associated proteins that link membrane proteins with actin filaments in the cell cortex and regulate many cellular processes, including cell shape determination, membrane transport, and signal transduction. Lymphocytes predominantly express two ERM members, ezrin and moesin. Mutations in the moesin gene in humans are associated with primary immunodeficiency with profound lymphopenia, and moesin-deficient mice exhibit a similar lymphopenia phenotype. In this study, we show that aging moesin-deficient mice develop a systemic lupus erythematosus-like autoimmune phenotype, which is characterized by elevated serum autoantibody levels and glomerulonephritis. Younger moesin-deficient mice exhibited elevated basal levels of several Ig isotypes and enhanced Ab affinity maturation upon immunization. Germinal center B cells and follicular helper T cells spontaneously accumulated in unimmunized mice, and CD8+CD44+CD122+Ly49+ regulatory T (CD8+ Tregs) cells, which inhibit the expansion of follicular helper T cells, were severely reduced in these mice. Isolated CD8+ Treg cells from moesin-deficient mice showed impaired proliferation in response to IL-15, which was accompanied by defects in STAT5 activation and IL-15Rα internalization, suggesting that moesin plays a key role in IL-15-mediated signaling. These findings underscore the importance of moesin in IL-15-dependent CD8+ Treg cell homeostasis and, thus, the control of self-tolerance.

Impaired lymphocyte trafficking in mice deficient in the kinase activity of PKN1.

Knock-in mice lacking PKN1 kinase activity were generated by introducing a T778A point mutation in the catalytic domain. PKN1[T778A] mutant mice developed to adulthood without apparent external abnormalities, but exhibited lower T and B lymphocyte counts in the peripheral blood than those of wild-type (WT) mice. T and B cell development proceeded in an apparently normal fashion in bone marrow and thymus of PKN1[T778A] mice, however, the number of T and B cell counts were significantly higher in the lymph nodes and spleen of mutant mice in those of WT mice. After transfusion into WT recipients, EGFP-labelled PKN1[T778A] donor lymphocytes were significantly less abundant in the peripheral circulation and more abundant in the spleen and lymph nodes of recipient mice compared with EGFP-labelled WT donor lymphocytes, likely reflecting lymphocyte sequestration in the spleen and lymph nodes in a cell-autonomous fashion. PKN1[T778A] lymphocytes showed significantly lower chemotaxis towards chemokines and sphingosine 1-phosphate (S1P) than WT cells in vitro. The biggest migration defect was observed in response to S1P, which is essential for lymphocyte egress from secondary lymphoid organs. These results reveal a novel role of PKN1 in lymphocyte migration and localization.

Moesin regulates neutrophil rolling velocity in vivo.

During inflammation, the selectin-induced slow rolling of neutrophils on venules cooperates with chemokine signaling to mediate neutrophil recruitment into tissues. Previous studies identified P-selectin glycoprotein ligand-1 (PSGL-1) and CD44 as E-selectin ligands that activate integrins to induce slow rolling. We show here that in TNF-α-treated cremaster muscle venules, slow leukocyte rolling was impaired in mice deficient in moesin, a member of the ezrin-radixin-moesin (ERM) family. Accordingly, neutrophil recruitment in a peritonitis model was decreased in moesin-deficient mice when chemokine signaling was blocked with pertussis toxin. These results suggest that moesin contributes to the slow rolling and subsequent recruitment of neutrophils during inflammation.

Glycosylation Status of CD43 Protein Is Associated with Resistance of Leukemia Cells to CTL-Mediated Cytolysis.

To improve cancer immunotherapy, it is important to understand how tumor cells counteract immune-surveillance. In this study, we sought to identify cell-surface molecules associated with resistance of leukemia cells to cytotoxic T cell (CTL)-mediated cytolysis. To this end, we first established thousands of monoclonal antibodies (mAbs) that react with MLL/AF9 mouse leukemia cells. Only two of these mAbs, designated R54 and B2, bound preferentially to leukemia cells resistant to cytolysis by a tumor cell antigen-specific CTLs. The antigens recognized by these mAbs were identified by expression cloning as the same protein, CD43, although their binding patterns to subsets of hematopoietic cells differed significantly from each other and from a pre-existing pan-CD43 mAb, S11. The epitopes of R54 and B2, but not S11, were sialidase-sensitive and expressed at various levels on leukemia cells, suggesting that binding of R54 or B2 is associated with the glycosylation status of CD43. R54high leukemia cells, which are likely to express sialic acid-rich CD43, were highly resistant to CTL-mediated cytolysis. In addition, loss of CD43 in leukemia cells or neuraminidase treatment of leukemia cells sensitized leukemia cells to CTL-mediated cell lysis. These results suggest that sialic acid-rich CD43, which harbors multiple sialic acid residues that impart a net negative surface charge, protects leukemia cells from CTL-mediated cell lysis. Furthermore, R54high or B2high leukemia cells preferentially survived in vivo in the presence of adaptive immunity. Taken together, these results suggest that the glycosylation status of CD43 on leukemia is associated with sensitivity to CTL-mediated cytolysis in vitro and in vivo. Thus, regulation of CD43 glycosylation is a potential strategy for enhancing CTL-mediated immunotherapy.

Upregulated CCL28 expression in the nasal mucosa in experimental allergic rhinitis: Implication for CD4(+) memory T cell recruitment.

During nasal immune responses, lymphocytes activated in the nasopharynx-associated lymphoid tissue (NALT) are thought to traffic to the nasal mucosa. Here we found a prominent infiltration of CD4(+) memory T cells into the nasal mucosa in a mouse model of allergic rhinitis. CCR3 and CCR10 mRNA was increased in the NALT, and CCR3- or CCR10-expressing CD4(+) T cells were present in the nasal mucosa. CCL28, a chemokine ligand for CCR3 and CCR10, was upregulated in nasal epithelial cells. Our results suggest that memory CD4(+) T cells traffic to the nasal mucosa in a process that may involve CCL28 and its receptors CCR3 and CCR10.

A novel splice variant of human L-selectin encodes a soluble molecule that is elevated in serum of patients with rheumatic diseases.

L-selectin, a type I membrane protein, is a leukocyte adhesion molecule that mediates both lymphocyte homing to peripheral lymph nodes and leukocyte accumulation at sites of inflammation. L-selectin is rapidly shed from the cell surface after cellular activation, and the ectodomain thus released is thought to account for high levels of soluble L-selectin in serum. In this study, we report the identification of a novel, naturally occurring isoform of the human L-selectin gene. Sequence analysis revealed that this isoform is generated by an alternative splicing event: the 7th exon of the human L-selectin gene, which encodes the region containing the transmembrane domain, is excluded, predicting a soluble protein product. The mRNA for this splice variant was expressed in lymphoid organs, where conventional L-selectin mRNA was also expressed. Activating T cells increased the variant mRNA and its ratio to the membrane form. Soluble L-selectin translated from the variant mRNA was present in human serum, albeit at a much lower level than that arising from ectodomain shedding, and was markedly elevated in patients with various rheumatic diseases, including rheumatoid arthritis and systemic lupus erythematosus. These observations indicate that some of the soluble L-selectin present in human serum arises through alternative splicing, which may be upregulated during lymphocyte activation in patients with various clinical conditions.

Moesin controls clathrin-mediated S1PR1 internalization in T cells.

The lipid mediator sphingosine 1-phosphate (S1P) regulates a wide range of cellular activities, including vascular maturation, angiogenesis, and immune-cell trafficking. Among the five known receptors for S1P (S1PR1-S1PR5), S1PR1 is a critical regulator of lymphocyte trafficking: its signaling is required for lymphocyte egress from lymphoid organs, while its down-modulation by agonist-induced internalization is a prerequisite for lymphocyte entry into lymphoid organs from the bloodstream. Despite the importance of S1PR1 down-regulation in determining lymphocyte behavior, the molecular mechanism of its internalization in lymphocytes has not been defined. Here we show that agonist-induced S1PR1 internalization in T cells occurs via clathrin-mediated endocytosis and is regulated by moesin, an ezrin-radixin-moesin (ERM) family member. In S1P-stimulated T cells, S1PR1 relocalized within clathrin-coated vesicles (CCVs) and early endosomes, and S1PR1 internalization was blocked when clathrin was pharmacologically inhibited. Stimulating moesin-deficient T cells with S1P failed to induce S1PR1 internalization and CCV formation. Furthermore, treating moesin-deficient mice with FTY720, an S1P receptor agonist known to internalize S1PR1, caused delayed lymphopenia, and lymphocytes isolated from FTY720-treated moesin-deficient mice still responded to S1P ex vivo in chemotaxis assays. These results reveal a novel role for moesin in regulating clathrin-dependent S1PR1 internalization through CCV formation.

Prostaglandin E2 promotes Th1 differentiation via synergistic amplification of IL-12 signalling by cAMP and PI3-kinase.

T helper 1 (Th1) cells have critical roles in various autoimmune and proinflammatory diseases. cAMP has long been believed to act as a suppressor of IFN-γ production and Th1 cell-mediated immune inflammation. Here we show that cAMP actively promotes Th1 differentiation by inducing gene expression of cytokine receptors involved in this process. PGE2 signalling through EP2/EP4 receptors mobilizes the cAMP-PKA pathway, which induces CREB- and its co-activator CRTC2-mediated transcription of IL-12Rß2 and IFN-γR1. Meanwhile, cAMP-mediated suppression of T-cell receptor signalling is overcome by simultaneous activation of PI3-kinase through EP2/EP4 and/or CD28. Loss of EP4 in T cells restricts expression of IL-12Rß2 and IFN-γR1, and attenuates Th1 cell-mediated inflammation in vivo. These findings clarify the molecular mechanisms and pathological contexts of cAMP-mediated Th1 differentiation and have clinical and therapeutic implications for deployment of cAMP modulators as immunoregulatory drugs.

Prostanoids as regulators of innate and adaptive immunity.

Potent, oxygenated lipid molecules called prostanoids regulate a wide variety of physiological responses and pathological processes. Prostanoids are produced by various cell types and act on target cells through specific G protein-coupled receptors. Although prostanoids have historically been considered acute inflammation mediators, studies using specific receptor knockout mice indicate that prostanoids, in fact, regulate various aspects of both innate and adaptive immunity. Each prostanoid, depending on which receptor it acts on, exerts specific effects on immune cells such as macrophages, dendritic cells, and T and B lymphocytes, often in concert with microbial ligands and cytokines, to affect the strength, quality, and duration of immune responses. Prostanoids are also relevant to immunopathology, from inflammation to autoimmunity and cancer. Here, we review the role of prostanoids in regulating immunity, their involvement in immunopathology, and areas of insight that may lead to new therapeutic opportunities.

Moesin-deficient mice reveal a non-redundant role for moesin in lymphocyte homeostasis.

Moesin is a member of the ezrin-radixin-moesin (ERM) family of cytoskeletal proteins. These proteins organize membrane domains by interacting with plasma membrane proteins and the actin cytoskeleton. Because of their high sequence similarity, ERM proteins are usually thought to be functionally redundant. Lymphocytes express two ERM proteins, ezrin and moesin. Whether each ERM plays a specialized role in lymphocytes, particularly in vivo, remains unknown. Here, we show that moesin has a crucial, non-redundant role in lymphocyte homeostasis. Moesin-deficient mice exhibited decreases in both T and B cells in the peripheral blood and lymph nodes, but not in the spleen. This phenotype was recapitulated in bone marrow (BM) chimeras with a hematopoietic moesin deficiency. Although the T and B cells apparently developed without major defects in the moesin-deficient mice, T cell egress from the thymus and immature B cell egress from the BM were impaired. In the periphery, both T and B cells showed delayed egress from lymphoid organs. We showed that moesin is the primary phosphorylated ERM subject to dynamic regulation during cell shape changes and migration. Our findings identify a previously unknown, non-redundant function of moesin in lymphocyte homeostasis in regulating lymphocyte egress from lymphoid organs.

A GPR40 agonist GW9508 suppresses CCL5, CCL17, and CXCL10 induction in keratinocytes and attenuates cutaneous immune inflammation.

G-protein coupled receptors (GPCR) exert diverse physiological functions, many of which are exploited therapeutically. The roles of GPCR in keratinocytes in immune response in the skin, however, remain poorly defined. In this study, we focused on Gi-coupled GPCR in keratinocytes and defined their actions in immunoactivation of cultured keratinocytes in vitro and immune reaction in the skin in vivo. We first activated HaCaT cells by tumor necrosis factor (TNF)-α and IFN-γ and examined effects of various ligands for GPCR on production of CCL17 and CCL5. Agonists for Gi-coupled receptors, particularly GW9508 for GPR40, inhibited CCL17 and CCL5 expression in a pertussis toxin-sensitive manner. The inhibitory effect by GW9508 was abrogated by depletion of GPR40 with RNA interference. GW9508 further suppressed expression of IL-11, IL-24, and IL-33 induced in HaCaT cells by TNF-α and IFN-γ. GW9508 also inhibited CCL5 and CXCL10 production by normal human epidermal keratinocytes. Administration of GW9508 topically to the skin in the challenging phase suppressed ear swelling in a repeated hapten application model and contact hypersensitivity with downregulation of CCL5 and CXCL10, respectively. Thus, in the skin, stimulation of Gi-coupled receptors attenuates induction of critical cytokines and chemokines by proinflammatory cytokines in keratinocytes and suppresses allergic inflammation in the skin.