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.

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.

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.

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.

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.

Prostaglandin E2-prostaglandin E receptor subtype 4 (EP4) signaling mediates UV irradiation-induced systemic immunosuppression.

UV radiation induces systemic immunosuppression. Because nonsteroidal anti-inflammatory drugs suppress UV-induced immunosuppression, prostanoids have been suspected as a crucial mediator of this UV effect. However, the identity of the prostanoid involved and its mechanism of action remain unclear. Here, we addressed this issue by subjecting mice deficient in each prostanoid receptor individually or mice treated with a subtype-specific antagonist to UV irradiation. Mice treated with an antagonist for prostaglandin E receptor subtype 4 (EP4), but not those deficient in other prostanoid receptors, show impaired UV-induced immunosuppression, whereas administration of an EP4 agonist rescues the impairment of the UV-induced immunosuppression in indomethacin-treated mice. The EP4 antagonist treatment suppresses an increase in the number of CD4(+)/forkhead box P3-positive (Foxp3(+)) regulatory T cells (Treg cells) in the peripheral lymph nodes (LNs) and dendritic cells expressing DEC205 in the LNs and the skin after UV irradiation. Furthermore, the EP4 antagonist treatment down-regulates UV-induced expression of receptor activator of NF-κB ligand (RANKL) in skin keratinocytes. Finally, administration of anti-RANKL antibody abolishes the restoration of UV-induced immunosuppression by EP4 agonism in indomethacin-treated mice. Thus, prostaglandin E(2) (PGE(2))-EP4 signaling mediates UV-induced immunosuppression by elevating the number of Treg cells through regulation of RANKL expression in the epidermis.

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.

Nepmucin, a novel HEV sialomucin, mediates L-selectin-dependent lymphocyte rolling and promotes lymphocyte adhesion under flow.

Lymphocyte trafficking to lymph nodes (LNs) is initiated by the interaction between lymphocyte L-selectin and certain sialomucins, collectively termed peripheral node addressin (PNAd), carrying specific carbohydrates expressed by LN high endothelial venules (HEVs). Here, we identified a novel HEV-associated sialomucin, nepmucin (mucin not expressed in Peyer's patches [PPs]), that is expressed in LN HEVs but not detectable in PP HEVs at the protein level. Unlike conventional sialomucins, nepmucin contains a single V-type immunoglobulin (Ig) domain and a mucin-like domain. Using materials affinity-purified from LN lysates with soluble L-selectin, we found that two higher molecular weight species of nepmucin (75 and 95 kD) were decorated with oligosaccharides that bind L-selectin as well as an HEV-specific MECA-79 monoclonal antibody. Electron microscopic analysis showed that nepmucin accumulates in the extended luminal microvillus processes of LN HEVs. Upon appropriate glycosylation, nepmucin supported lymphocyte rolling via its mucin-like domain under physiological flow conditions. Furthermore, unlike most other sialomucins, nepmucin bound lymphocytes via its Ig domain, apparently independently of lymphocyte function-associated antigen 1 and very late antigen 4, and promoted shear-resistant lymphocyte binding in combination with intercellular adhesion molecule 1. Collectively, these results suggest that nepmucin may serve as a dual-functioning PNAd in LN HEVs, mediating both lymphocyte rolling and binding via different functional domains.

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.

P-selectin glycoprotein ligand-1 negatively regulates T-cell immune responses.

Cell surface sialomucins often act as antiadhesive molecules by virtue of their extended structure and negative charge. CD43 is one such sialomucin, expressed on most leukocytes. P-selectin glycoprotein ligand-1 (PSGL-1) is another sialomucin expressed by leukocytes. It serves as a major selectin ligand, but no antiadhesive role for it has been described. In this study, we showed that PSGL-1-deficient T cells, like CD43-deficient T cells, exhibited increased adhesion and proliferation compared with wild-type cells. The loss of both PSGL-1 and CD43 led to a further increase in T cell adhesion and proliferation. The reexpression of full-length PSGL-1 or CD43 in double-deficient CD4(+) T cells reversed their increased adhesion and proliferation phenotype. Using chimeric constructs of human CD8 and either PSGL-1 or CD43, we demonstrated that the intracellular domain of PSGL-1 or CD43 is required for suppressing proliferation but not adhesion. Furthermore, in a mouse model of inflammatory bowel disease induced by the adoptive transfer of naive T cells into RAG-deficient hosts, a PSGL-1 deficiency exacerbated the development of inflammation. These results reveal a novel regulatory role for PSGL-1 in T cell adhesion and proliferation and suggest that PSGL-1 negatively regulates T cell immune responses in vivo.

Constitutive expression of IDO by dendritic cells of mesenteric lymph nodes: functional involvement of the CTLA-4/B7 and CCL22/CCR4 interactions.

Dendritic cells (DCs) express the immunoregulatory enzyme IDO in response to certain inflammatory stimuli, but it is unclear whether DCs express this enzyme under steady-state conditions in vivo. In this study, we report that the DCs in mesenteric lymph nodes (MLNs) constitutively express functional IDO, which metabolizes tryptophan to kynurenine. In line with a previous report that regulatory T cells (Tregs) can induce IDO in DCs via the CTLA-4/B7 interaction, a substantial proportion of the MLN DCs were located in juxtaposition to Tregs, whereas this tendency was not observed for splenic DCs, which do not express IDO constitutively. When CTLA-4 was selectively deleted in Tregs, the frequency of IDO-expressing DCs in MLNs decreased significantly, confirming CTLA-4's role in IDO expression by MLN DCs. We also found that the MLN DCs produced CCL22, which can attract Tregs via CCR4, and that the phagocytosis of autologous apoptotic cells induced CCL22 expression in CCL22 mRNA-negative DCs. Mice genetically deficient in the receptor for CCL22, CCR4, showed markedly reduced IDO expression in MLN-DCs, supporting the involvement of the CCL22/CCR4 axis in IDO induction. Together with our previous observation that MLN DCs contain much intracytoplasmic cellular debris in vivo, these results indicate that reciprocal interactions between the DCs and Tregs via both B7/CTLA-4 and CCL22/CCR4 lead to IDO induction in MLN DCs, which may be initiated and/or augmented by the phagocytosis of autologous apoptotic cells by intestinal DCs. Such a mechanism may help induce the specific milieu in MLNs that is required for the induction of oral tolerance.

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.

An L-selectin ligand distinct from P-selectin glycoprotein ligand-1 is expressed on endothelial cells and promotes neutrophil rolling in inflammation.

Neutrophils recruited from the blood are key players in the innate immune response. Selectins play critical roles in neutrophil recruitment by mediating their tethering and rolling in inflamed venules. While the roles of P- and E-selectin in this process are well established, the mechanisms of L-selectin-mediated neutrophil recruitment remain elusive. One proposal is that tethering is mediated by L-selectin on flowing neutrophils interacting with P-selectin glycoprotein ligand-1 (PSGL-1) on adherent neutrophils. To clarify whether L-selectin-mediated neutrophil recruitment depends entirely on PSGL-1, we examined the impact of L-selectin deficiency in mice with a PSGL-1-deficient background. L-selectin and PSGL-1 double-knockout mice exhibited a higher increase in their peripheral blood neutrophil count and a worse defect in neutrophil recruitment into the inflamed peritoneum than PSGL-1-deficient mice. Intravital microscopy of inflamed cremaster muscle venules showed that L-selectindeficiency or antibody blockade of L-selectin reduced the residual leukocyte rolling in PSGL-1-deficient mice. Flow cytometric analyses showed that the endothelial cells from the cremaster muscle bound L-selectin in a PSGL-1-independent manner. These results provide evidence for the existence of an L-selectin ligand distinct from PSGL-1 in inflammation and indicate that such a ligand is expressed on endothelial cells, promoting neutrophil rolling in vivo.

CD43 plays both antiadhesive and proadhesive roles in neutrophil rolling in a context-dependent manner.

As the first step in the recruitment of neutrophils into tissues, the cells become tethered to and roll on the vessel wall. These processes are mediated by interactions between the P- and E-selectins, expressed on the endothelial cells of the vessel wall, and their ligands, expressed on the neutrophils. Recently, we reported that CD43 on activated T cells functions as an E-selectin ligand and thereby mediates T cell migration to inflamed sites, in collaboration with P-selectin glycoprotein ligand-1 (PSGL-1), a major P- and E-selectin ligand. Here, we examined whether CD43 on neutrophils also functions as an E-selectin ligand. CD43 was precipitated with an E-selectin-IgG chimera from mouse bone marrow neutrophils. A CD43 deficiency diminished the E-selectin-binding activity of neutrophils when PSGL-1 was also deficient. Intravital microscopy showed that the CD43 deficiency significantly increased leukocyte rolling velocities in TNF-alpha-stimulated venules blocked with an anti-P-selectin mAb, where the rolling was mostly E-selectin dependent, when PSGL-1 was also absent. In contrast, in venules with trauma-induced inflammation, where the rolling was largely P-selectin dependent, the CD43 deficiency reduced leukocyte rolling velocities. Collectively, these observations suggest that CD43 generally serves as an antiadhesive molecule to attenuate neutrophil-endothelial interactions, but when E-selectin is expressed on endothelial cells, it also plays a proadhesive role as an E-selectin ligand.

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.

CD4+CD25+ regulatory T cells in the small intestinal lamina propria show an effector/memory phenotype.

CD4(+)CD25(+) regulatory T cells (Tregs) have been implicated in the suppression of pathogenic responses to both self- and non-self-antigens in the intestine. However, their precise properties and functions in the gut, as well as the molecular basis of their recruitment to the gut, are poorly understood. Here, we found that most of the CD4(+)CD25(+) T cells in the small intestinal lamina propria (LP) express Foxp3 and exhibit an 'effector/memory' phenotype, CD44(hi)CD45RB(lo)CD62L(-), whereas only a minority of the Foxp3(+)CD4(+)CD25(+) T cells in the spleen and mesenteric lymph nodes showed this phenotype. The Tregs in the small intestinal LP (LP-Tregs) expressed higher levels of CCR4 and CCR9 and a substantially lower level of CCR7 than the Tregs in the spleen. In vitro, the LP-Tregs showed chemotaxis to CCL25/thymus-expressed chemokine. In addition, they showed efficient chemotaxis to the CCR4 ligands, CCL17/thymus and activation-regulated chemokine and CCL22/macrophage-derived chemokine, which are abundantly expressed by dendritic cells (DCs) in the small intestinal LP. In vivo, approximately 50% of the LP-Tregs were closely associated or in direct contact with LP-DCs. These findings demonstrate that LP-Tregs are phenotypically and functionally unique and raise the possibility that they are retained in the small intestinal LP through the action of CCL17 and CCL22, which are locally produced by LP-DCs.