Possible involvement of soluble B7-H4 in T cell-mediated inflammatory immune responses

Soluble form of immune checkpoints in autoimmune diseases

Immune checkpoints are essential regulators of immune responses, either by activating or suppressing them. Consequently, they are regarded as pivotal elements in the management of infections, cancer, and autoimmune disorders. In recent years, researchers have identified numerous soluble immune checkpoints that are produced through various mechanisms and demonstrated biological activity. These soluble immune checkpoints can be produced and distributed in the bloodstream and various tissues, with their roles in immune response dysregulation and autoimmunity extensively documented. This review aims to provide a thorough overview of the generation of various soluble immune checkpoints, such as sPD-1, sCTLA-4, sTim-3, s4-1BB, sBTLA, sLAG-3, sCD200, and the B7 family, and their importance as indicators for the diagnosis and prediction of autoimmune conditions. Furthermore, the review will investigate the potential pathological mechanisms of soluble immune checkpoints in autoimmune diseases, emphasizing their association with autoimmune diseases development, prognosis, and treatment.

Prognostic Role of Soluble and Extracellular Vesicle-Associated PD-L1, B7-H3 and B7-H4 in Non-Small Cell Lung Cancer Patients Treated with Immune Checkpoint Inhibitors

The treatment of non-small cell lung cancer (NSCLC) has changed dramatically with the advent of immune checkpoint inhibitors (ICIs). Despite encouraging results, their efficacy remains limited to a subgroup of patients. Circulating immune checkpoints in soluble (s) form and associated with extracellular vesicles (EVs) represent promising markers, especially in ICI-based therapeutic settings. We evaluated the prognostic role of PD-L1 and of two B7 family members (B7-H3, B7-H4), both soluble and EV-associated, in a cohort of advanced NSCLC patients treated with first- (n = 56) or second-line (n = 126) ICIs. In treatment-naïve patients, high baseline concentrations of sPD-L1 (>24.2 pg/mL) were linked to worse survival, whereas high levels of sB7-H3 (>0.5 ng/mL) and sB7-H4 (>63.9 pg/mL) were associated with better outcomes. EV characterization confirmed the presence of EVs positive for PD-L1 and B7-H3, while only a small portion of EVs expressed B7-H4. The comparison between biomarker levels at the baseline and in the first radiological assessment under ICI-based treatment showed a significant decrease in EV-PD-L1 and an increase in EV-B7H3 in patients in the disease response to ICIs. Our study shows that sPD-L1, sB7-H3 and sB7-H4 levels are emerging prognostic markers in patients with advanced NSCLC treated with ICIs and suggests potential EV involvement in the disease response to ICIs.

The immunological role of b7-h4 in pregnant women with sars-cov2 infection

Problem

T‐cells are key players in fighting the coronavirus disease 2019 (COVID‐19). The checkpoint molecule B7‐H4, a member of the B7 family, can inhibit T‐cell activation and proliferation by inhibiting NF‐kb expression. We aimed to elucidate the immunological role of soluble B7‐H4 (sB7‐H4) and B7‐H4 in pregnant women suffered from an acute Sars‐Cov2 infection.

Methods

Expression levels of sB7‐H4 and cytokines were detected by enzyme linked immunosorbent assay. B7‐H4 and cytokines mRNA expression was analyzed by qPCR, and B7‐H4 and NF‐κb (p65) protein levels were investigated by western blot and immunofluorescence staining in placenta chorionic villous and decidual basalis tissues of COVID‐19 affected women and healthy controls.

Results

Fibrinoid necrosis in the periphery of placental villi was increased in the COVID‐19‐affected patients. sB7‐H4 protein in maternal and cord blood serum and IL‐6/IL‐10 were increased while leukocytes were decreased during SARS‐CoV‐2 infection. Serum sB7‐H4 level was increased according to the severity of SARS‐Cov‐2 infection. Cytokines (IL‐6, IL‐18, IL‐1β, TNF‐α), B7‐H4 mRNA and protein in the decidual basalis tissues of COVID‐19‐infected pregnant women were significantly increased compared to healthy controls. IL‐18 and IL‐1β were significantly increased in the placenta chorionic villous samples of COVID‐19 affected patients, while NF‐κb (p65) expression was decreased.

Conclusions

The expression of the immunological marker sB7‐H4 correlated with the severity of COVID‐19 disease in pregnant women. sB7‐H4 and B7‐H4 can be used to monitor the progression of COVID‐19 infection during pregnancy, and for evaluating of the maternal immune status.

A Potential Role of B7-H4 Expression in Predicting the Recurrence of Chronic Rhinosinusitis with Nasal Polyps

Background

Chronic rhinosinusitis with polyps (CRSwNP) is a common chronic inflammatory disease of the nasal cavity and sinuses with a high rate of postoperative recurrence. In this study, we aim to investigate the expression of B7-H4 in CRSwNP and its association with postoperative recurrence.

Methods

A total of 80 CRSwNP patients, including 40 primary CRSwNP (pCRSwNP) patients and 40 recurrent CRSwNP (rCRSwNP) patients, 27 chronic rhinosinusitis without polyps (CRSsNP) and 32 healthy controls (HC) were enrolled in this study, and the serum, nasal polyps and middle turbinate tissue samples were collected. Peripheral and tissue B7-H4 expressions were detected by enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence, and their clinical values in predicting postoperative recurrence of CRSwNP were evaluated.

Results

We identified significantly higher tissue B7-H4 mRNA levels in the CRSwNP group than in the HC group, and elevated B7-H4 levels were associated with tissue eosinophil count and percentage (r = 0.469, P < 0.001; r = 0.521, P < 0.001). B7-H4 mRNA and protein levels were significantly higher in the rCRSwNP group than the pCRSwP group. Multivariate analysis and receiver operating characteristic (ROC) curves showed that tissue B7-H4 levels were associated with postoperative recurrence in patients with CRSwNP (P < 0.05). In addition, serum B7-H4 levels were significantly increased in the CRSwNP group than the CRS and HC groups, especially in the rCRSwNP group (P < 0.05), and the ROC curve presented a predictive ability of serum B7-H4 in predicting postoperative recurrence.

Conclusion

Our results indicated that B7-H4 level was clearly enhanced in CRSwNP patients and associated with postoperative recurrence. Serum B7-H4 might serve as a simple and convenient biomarker for early predicting postoperative recurrence in CRwNP patients.

Expression of the Costimulatory Molecule B7-H4 in the Decidua and Placental Tissues in Patients with Placental Abruption

B7 homolog 4 protein (B7-H4), a member of the B7 family, is a immunomodulatory membrane protein. The aim of the study was to evaluate the expression of this protein in the decidua and placental tissues in case of placental abruption (PA) compared to cases of retained placental tissue (RPT) and controls. Tissue samples were obtained from 47 patients with PA, 60 patients with RPT, and 41 healthy controls. The samples were stained for B7-H4 expression, analyzed by an expert pathologist, and a semi-quantitative scale was applied. A statistical analysis revealed that the expression of B7-H4 was significantly higher in the decidua in PA samples compared to samples from patients with RPT (p-value < 0.001) and healthy controls (p-value < 0.001). The expression of B7-H4 in the placental chorionic villus was significantly higher in PA samples in relation to samples from healthy controls (p-value < 0.001) but not in relation to RPT samples (p-value = 0.0853). This finding suggests that B7-H4 might play an important role in mechanisms restoring reproductive tract homeostasis. Further research is necessary in regard to the role of B7-H4 in PA.

Association of Soluble B7-H4 and Circulating Tumor Cells in Blood of Advanced Epithelial Ovarian Cancer Patients

Introduction

Epithelial ovarian cancer (EOC) is the deadliest gynecologic malignancy worldwide. Reliable predictive biomarkers are urgently needed to estimate the risk of relapse and to improve treatment management. Soluble immune-checkpoints in EOC are promising molecules serving as prognostic biomarkers accessible via liquid biopsy. We thus, aimed at elucidating the role of sB7-H4 in EOC.

Material and Methods

We analyzed soluble serum B7-H4 (sB7-H4) using ELISA and circulating tumor cells (CTCs) in blood applying the AdnaTest OvarianCancer in 85 patients suffering from advanced EOC. Findings were correlated with clinical parameters as well as survival data.

Results

sB7-H4 was detectable in 14.1% patients, CTCs in 32.9% patients and simultaneous presence of CTCs and sB7-H4 was found in 7% patients, respectively. Although no association between sB7-H4 and CTC could be documented, each of them served as independent predictive factors for overall survival (OS).

Conclusion

sB7-H4 and CTCs are independent prognostic biomarkers for impaired survival in EOC. As they are easily accessible via liquid biopsy, they may be of potential benefit for the prediction of therapy response and survival for EOC patients.

Soluble B7-CD28 Family Inhibitory Immune Checkpoint Proteins and Anti-Cancer Immunotherapy

Co-inhibitory B7-CD28 family member proteins negatively regulate T cell responses and are extensively involved in tumor immune evasion. Blockade of classical CTLA-4 (cytotoxic T lymphocyte-associated antigen-4) and PD-1 (programmed cell death protein-1) checkpoint pathways have become the cornerstone of anti-cancer immunotherapy. New inhibitory checkpoint proteins such as B7-H3, B7-H4, and BTLA (B and T lymphocyte attenuator) are being discovered and investigated for their potential in anti-cancer immunotherapy. In addition, soluble forms of these molecules also exist in sera of healthy individuals and elevated levels are found in chronic infections, autoimmune diseases, and cancers. Soluble forms are generated by proteolytic shedding or alternative splicing. Elevated circulating levels of these inhibitory soluble checkpoint molecules in cancer have been correlated with advance stage, metastatic status, and prognosis which underscore their broader involvement in immune regulation. In addition to their potential as biomarker, understanding their mechanism of production, biological activity, and pathological interactions may also pave the way for their clinical use as a therapeutic target. Here we review these aspects of soluble checkpoint molecules and elucidate on their potential for anti-cancer immunotherapy.

Establishment of a novel double-monoclonal antibody sandwich enzyme-linked immunosorbent assay (ELISA): tool for human B7-H4 detection in autoimmune diseases

B7-H4, one of the immunoregulatory proteins, plays an inhibitory role by inhibiting T cell proliferation and cytokine production. Nevertheless, the significance of soluble B7-H4 (sB7-H4) in autoimmune diseases is unclear. In our study, we developed two novel mouse anti-human B7-H4 monoclonal antibodies (mAbs) (clones 8D4 and 7E1) with utilities for flow cytometry, immunoblotting and immunofluorescence. We characterized 7E1 as a functional antibody with antagonistic activity, which could promote T cell proliferation and regulate cytokine production. Furthermore, based on the different epitope specificities, we established a novel enzyme-linked immunosorbent assay (ELISA) which could detect sB7-H4 sensitively and specifically. Using this ELISA kit, sB7-H4 was observed in a high proportion of autoimmune diseases patients. We found that the levels of sB7-H4 were significantly higher in patients with systemic lupus erythematosus (SLE), type I diabetes (T1D) and Graves' disease (GD). Together, sB7-H4 in human serum is regarded not only as a regulator of T cell activation but may also be a diagnostic marker of autoimmune diseases.

Predictive value of serum soluble B7-H4 in acute pancreatitis

BACKGROUND

Studies reported that soluble B7-H4 (sB7-H4) was significantly related to the progression and prognosis of inflammatory diseases, and whether sB7-H4 is related to the severity and prognosis of acute pancreatitis (AP) timely has not been reported.

MATERIALS AND METHODS

Clinical database data of 446 AP patients were retrospectively collected, and the correlation between the expression serum levels of sB7-H4 with inflammatory factors and prognostic scores was analysed in AP patients.

RESULTS

Soluble B7-H4 was significantly correlated with IL-6, IL-8, TNF-α, PCT, CRP levels and WBC count (P < .01), with correlation coefficients of R = .61, .53, .46, .60, .57 and .47, respectively, and AUCs were 0.905, 0.837, 0.797, 0.858, 0.890, 0.841 and 0.855, respectively. In addition, sB7-H4 was significantly correlated with the Ranson score, APACHE II score and BISAP score (P < .001), with correlation coefficients of R = .58, .63 and .59, respectively. The AUCs of assessing local complications of AP were 0.908, 0.863, 0.785 and 0.844, respectively; assessing organ failure were 0.872, 0.790, 0.796 and 0.857, respectively; and assessing in-hospital mortality were 0.839, 0.821, 0.796 and 0.823, respectively.

CONCLUSIONS

Soluble B7-H4 could be used as a marker for the diagnosis, severity assessment and poor prognosis assessment of AP patients, which may have potential clinical applications.

B7-H4 Inhibits the Development of Primary Sjögren's Syndrome by Regulating Treg Differentiation in NOD/Ltj Mice

Background

This study is aimed at exploring the role of B7-H4 in the pathogenesis of primary Sjögren's syndrome (pSS) in NOD/Ltj mouse.

Methods

B7-H4 expression in salivary glands was examined by IHC, and lymphocyte infiltration was showed by H&E. Next, anti-B7-H4 mAb or immunoglobulin isotype was injected into NOD/Ltj mice. Cytokine levels were measured by quantitative RT-PCR, and immunoglobulins were measured by ELISA. T cell subsets were analyzed by flow cytometry. Last, we treated NOD/Ltj mice with B7-H4Ig and control Ig. CD4+Foxp3+ T cells were assessed by immunohistochemistry. Two-tailed Student's t-tests were used to detect the statistical difference in various measures between the two groups.

Results

B7-H4 expression was remarkably reduced in salivary glands of NOD/Ltj mice at 15 weeks compared with the NOD/Ltj mice at 8 weeks. Anti-B7-H4 mAb treatment increased lymphocyte infiltration in salivary glands. Inflammatory cytokines including IL-12, IL-18, IL-1α, TNF-α, IFN-α, and BAFF were upregulated markedly in anti-B7-H4 mAb-treated mice compared to IgG isotype-treated mice. Flow cytometry analysis showed that anti-B7-H4 mAb-treated mice had lower levels of CD4+Foxp3+/CD4+ T cells in spleen. Moreover, Foxp3 mRNA levels of salivary glands were diminished in anti-B7-H4 mAb-treated mice. Flow cytometry analysis showed that anti-B7-H4 mAb inhibited CD4+Foxp3+/CD4+ T cell production, while B7-H4Ig would promote naïve CD4+ T into Treg differentiation. Administration with B7-H4Ig displayed significantly decreased lymphocyte infiltration in salivary glands and low levels of total IgM and IgG in serum. Analysis of inflammatory cytokines in salivary glands after B7-H4Ig treatment revealed that the mRNA levels of IL-12, IL-6, IL-18, IL-1α, TNF-α, and IFN-α were significantly downregulated in B7-H4Ig-treated mice compared to control Ig treatment. B7-H4Ig-treated mice had significantly higher levels of CD4+Foxp3+/CD4+ T cells in spleen. IHC in salivary gland revealed that CD4+Foxp3+ T cells of B7-H4Ig treatment mouse were more than control Ig treatment.

Conclusions

Our findings implicate that B7-H4 has a protective role for salivary gland epithelial cells (SGECs) and therapeutic potential in the treatment of pSS.

B7-H4, a promising target for immunotherapy

The coinhibitory molecule B7-H4, an important member of the B7 family, is abnormally expressed in tumors, inflammation and autoimmune diseases. B7-H4 negatively regulates T cell immune response and promotes immune escape by inhibiting the proliferation, cytokine secretion, and cell cycle of T cells. Moreover, B7-H4 plays an extremely important role in tumorigenesis and tumor development including cell proliferation, invasion, metastasis, anti-apoptosis, etc. In addition, B7-H4 has the other biological functions, such as protection against type 1 diabetes (T1D) and islet cell transplantation. Therefore, B7-H4 has been identified as a novel marker or a therapeutic target for the treatment of tumors, inflammation, autoimmune diseases, and organ transplantation. Here, we summarized the expression profiles, physiological and pathological functions, and regulatory mechanisms of B7-H4, the signaling pathways involved, as well as B7-H4-based immunotherapy.

PD-L1 Gene Polymorphism and High Level of Plasma Soluble Pd-L1 Protein may be aSsociated with Non-Small Cell Lung Cancer

Background

PD-1 and its ligand PD-L1 belong to the co-inhibition molecules, which can downregulate immune responses. The PD-L1 polymorphism and the level of soluble PD-L1 (sPD-L1) were investigated in non-small cell lung cancer (NSCLC).

Methods

A total of 288 NSCLC patients and 300 controls were enrolled. An A/C polymorphism at position 8923 in the PD-L1 gene was genotyped using the polymerase chain reaction-restriction fragment length polymorphism method.

Results

The prevalence of the 8923C allele was significantly higher in NSCLC patients than controls (10.2% versus 5.3%, p = 0.002, odds ratio 2.03, 95% confidence interval 1.30-3.17; data were adjusted for age and sex). NSCLC patients also showed increased plasma levels of sPD-L1 compared to controls (1.92 ng/mL versus 0.91 ng/mL, p<0.001). Furthermore, lung adenocarcinoma patients had higher sPD-L1 levels than patients with squamous cell carcinoma (p<0.01). However, no association was observed between the different genetic variants and plasma concentrations of sPD-L1.

Conclusions

The PD-L1 8923A/C polymorphism could be associated with increased susceptibility to NSCLC. Plasma levels of sPD-L1 are significantly increased in NSCLC patients, especially those with adenocarcinoma.

Immune checkpoint receptors in regulating immune reactivity in rheumatic disease

Immune checkpoint regulators are critical modulators of the immune system, allowing the initiation of a productive immune response and preventing the onset of autoimmunity. Co-inhibitory and co-stimulatory immune checkpoint receptors are required for full T-cell activation and effector functions such as the production of cytokines. In autoimmune rheumatic diseases, impaired tolerance leads to the development of diseases such as rheumatoid arthritis, systemic lupus erythematosus, and Sjogren’s syndrome. Targeting the pathways of the inhibitory immune checkpoint molecules CD152 (cytotoxic T lymphocyte antigen-4) and CD279 (programmed death-1) in cancer shows robust anti-tumor responses and tumor regression. This observation suggests that, in autoimmune diseases, the converse strategy of engaging these molecules may alleviate inflammation owing to the success of abatacept (CD152-Ig) in rheumatoid arthritis patients. We review the preclinical and clinical developments in targeting immune checkpoint regulators in rheumatic disease.

Changes in the Blood Serum Levels of the Costimulatory Soluble B7-H4 Molecule in Pregnant Women During the Peripartal Phase

PROBLEM

B7-H4, a transmembrane protein that negatively regulates T lymphocytes, seems to play a role in the suppression of the im\mune response at the maternal-fetal interface. The aim of this study was to compare the blood serum concentration levels of soluble B7-H4 (sB7-H4) prepartal and postpartal in both women who experienced spontaneous onset of labor and those who underwent elective cesarian section.

METHOD OF STUDY

Blood was obtained from 30 prepartal and postpartal women who delivered at the University Hospital of Essen between 2011 and 2012. These patients were further divided into two subgroups depending on the advancement of labor. The sB7-H4 blood serum concentration levels of the women in the groups were then determined by ELISA (BIOZOL, Eching, Germany).

RESULTS

In women who underwent elective cesarian section, a significant increase in sB7-H4 blood serum concentration levels occurred postpartal, while in women who experienced spontaneous onset of labor, no differences between prepartal and postpartal concentration levels were observed. The sB7-H4 blood serum concentration levels on the day after delivery in the women who experienced spontaneous labor and those who underwent elective cesarian section were comparable; however, higher blood serum concentration levels of sB7-H4 were observed prepartal in women with spontaneous onset of labor compared to those found in the women about to undergo elective cesarian section.

CONCLUSION

These changes in sB7-H4 blood serum concentration levels suggest that this protein is involved in immunological changes associated with the spontaneous onset of labor and post-delivery homeostasis.

B7-H4's role "beyond the tumor"

B7-H4 is a ligand in the B7 costimulatory family, executing suppressive function on the immune system in many diseases, such as cancer, allograft rejection, and autoimmune diseases. The receptor for this molecule has yet to be clarified. The engagement of B7-H4 inhibits proliferation of immune cells by stopping the cell cycle at the G0/G1 phase and leads to apoptosis via the Fas/FasL pathway consequently accelerating tumor progression and alleviating allograft rejection. The pathogenic role of B7-H4 in tumors has been widely established, but few studies have focused on its function in other disorders. Here, we review recent advances in our understanding of B7-H4 biology in disease settings other than tumors and document the beneficial values to treat those diseases by targeting this molecule and related signaling pathways.

B7 family checkpoint regulators in immune regulation and disease

Fine-tuning the immune response and maintaining tolerance to self-antigens involves a complex network of co-stimulatory and co-inhibitory molecules. The recent FDA approval of ipilimumab, a monoclonal antibody blocking cytotoxic T lymphocyte antigen (CTLA)-4, demonstrates the impact of checkpoint regulators in disease. This is reinforced by ongoing clinical trials targeting not only CTLA-4, but also the programmed death (PD)-1 and B7-H4 pathways in various disease states. Recently, two new B7 family inhibitory ligands, V-domain Ig suppressor of T cell activation (VISTA) and B7-H6 were identified. Here, we review recent understanding of B7 family members and their concerted regulation of the immune response to either self or foreign pathogens. We also discuss clinical developments in targeting these pathways in different disease settings, and introduce VISTA as a putative therapeutic target.

Host b7x promotes pulmonary metastasis of breast cancer

B7x (B7-H4 or B7S1) is an inhibitory member of the B7 family of T cell costimulation. It is expressed in low levels in healthy peripheral tissues, such as the lung epithelium, but is overexpressed in a variety of human cancers with negative clinical associations, including metastasis. However, the function of B7x in the context of cancer, whether expressed on cancer cells or on surrounding "host" tissues, has not been elucidated in vivo. We used the 4T1 metastatic breast cancer model and B7x knockout (B7x (-/-)) mice to investigate the effect of host tissue-expressed B7x on cancer. We found that 4T1 cells were B7x negative in vitro and in vivo, and B7x(-/-) mice had significantly fewer lung 4T1 tumor nodules than did wild-type mice. Furthermore, B7x(-/-) mice showed significantly enhanced survival and a memory response to tumor rechallenge. Mechanistic studies revealed that the presence of B7x correlated with reduced general and tumor-specific T cell cytokine responses, as well as with an increased infiltration of immunosuppressive cells, including tumor-associated neutrophils, macrophages, and regulatory T cells, into tumor-bearing lungs. Importantly, tumor-associated neutrophils strongly bound B7x protein and inhibited the proliferation of both CD4 and CD8 T cells. These results suggest that host B7x may enable metastasizing cancer cells to escape local antitumor immune responses through interactions with the innate and adaptive immune systems. Thus, targeting the B7x pathway holds much promise for improving the efficacy of immunotherapy for metastatic cancer.

The costimulatory molecule B7-H4 promote tumor progression and cell proliferation through translocating into nucleus

B7-H4, a member of B7 family, is a transmembrane protein and inhibits T-cells immunity. However, in a variety of tumor cells, B7-H4 was detected predominantly in intracellular compartments with unknown mechanism and functions. In this study, we analyzed B7-H4 expression and subcellular distribution by immunohistochemistry in renal cell carcinoma (RCC) tissues. B7-H4 protein was detected on the membrane, in the cytosol and/or in the nucleus in tumor tissues. The membrane and nuclear expression of B7-H4 was significantly correlated with the tumor stages of RCC. Moreover, the membrane localization of B7-H4 was inversely correlated with the intensity of tumor infiltrates lymphocyte (TILs), whereas no association was observed between nuclear expression of B7-H4 and the density of TILs status. We further identified that B7-H4 is a cytoplasmic-nuclear shuttling protein containing a functional nuclear localization sequence (NLS) motif. A point mutation of B7-H4 NLS motif blocked the leptomycin B -induced nuclear accumulation of B7-H4. HEK293 cells stably expressing B7-H4 NLS mutant exhibited more potent inhibition in T-cell proliferation and cytokine production through increasing its surface expression compared with wild-type B7-H4 transfected cells owing to their increased surface expression. Most importantly, overexpression of wild-type B7-H4 in HEK293 cells enhanced tumor cell proliferation in vitro and tumorigenicity in vivo, promoted G1/S phase transition. The regulation of cell cycle by wild-type B7-H4 was partialy due to upregulation of Cyclin D 1 and Cyclin E. A mutation of B7-H4 NLS motif abolished the B7-H4-mediated cell proliferation and cell cycle regulation. Furthermore, B7-H4 wild-type confers chemoresistance activity to RCC cell lines including Caki-1 and ACHN. Our study provides a new insight into the functional implication of B7-H4 in its subcellular localization.

B7x in the periphery abrogates pancreas-specific damage mediated by self-reactive CD8 T cells

B7x (B7-H4 or B7S1) is the seventh member of the B7 family, and its in vivo function remains largely unknown. Despite new genetic data linking the B7x gene with autoimmune diseases, how exactly it contributes to peripheral tolerance and autoimmunity is unclear. In this study, we showed that B7x protein was not detected on APCs or T cells in both human and mice, which is unique in the B7 family. Because B7x protein is expressed in some peripheral cells such as pancreatic β cells, we used a CD8 T cell-mediated diabetes model (AI4αβ) in which CD8 T cells recognize an endogenous self-Ag, and found that mice lacking B7x developed more severe diabetes than control AI4αβ mice. Conversely, mice overexpressing B7x in the β cells (Rip-B7xAI4αβ) were diabetes free. Furthermore, adoptive transfer of effector AI4αβ CD8 T cells induced diabetes in control mice, but not in Rip-B7xAI4αβ mice. Mechanistic studies revealed that pathogenic effector CD8 T cells were capable of migrating to the pancreas but failed to robustly destroy tissue when encountering local B7x in Rip-B7xAI4αβ mice. Although AI4αβ CD8 T cells in Rip-B7xAI4αβ and AI4αβ mice showed similar cytotoxic function, cell death, and global gene expression profiles, these cells had greater proliferation in AI4αβ mice than in RIP-B7xAI4αβ mice. These results suggest that B7x in nonlymphoid organs prevents peripheral autoimmunity partially through inhibiting proliferation of tissue-specific CD8 T cells, and that local overexpression of B7x on pancreatic β cells is sufficient to abolish CD8 T cell-induced diabetes.

Tumor expression of B7-H4 predicts poor survival of patients suffering from gastric cancer

To establish the prognostic value of B7-H4 expression by tumor cells in gastric cancer patients, we evaluated the association of B7-H4 expression with clinicopathologic factors and overall survival of gastric cancer patients. A retrospective cohort study including 156 gastric cancer patients was performed in the present report. Immunohistochemical assay was used to evaluate the expression of B7-H4 in the surgical specimens of gastric cancer tissues. Multi-univariate COX model was then used to evaluate the association of B7-H4 expression with the patients' survival and clinicopathological parameters. B7-H4 expression in the gastric cancer cells was observed in about 44.9% gastric cancer specimens. Univariate analysis demonstrated that there was no correlation between B7-H4 expression and sex, age, histological type, pathological grade or tumor size. In contrast, B7-H4 expression correlated positively with cancer invasiveness and lymph node metastasis. In addition, the median overall survival time of patients with lower B7-H4 expression was 13 months longer than that of patients with higher expression (chi(2) = 12.38, P < 0.0001), and the median disease-free survival time of patients with lower B7-H4 expression was significantly longer than that of patients with higher expression (33 vs. 16 months, chi(2) = 14.977, P < 0.0001). After adjustment for other confounding factors, the COX model analysis indicated that the death risk was significantly higher in patients with higher B7-H4 expression than those with lower expression (RR = 1.85, 95% CI = 1.15-2.96). The present study demonstrated that higher B7-H4 expression in cancer cells was associated with poor prognosis of gastric cancer patients. This is consistent with the idea that B7-H4 promotes cancer progression, likely via inhibition of anti-tumor immune responses.

In vivo function of immune inhibitory molecule B7-H4 in alloimmune responses

B7 ligands deliver both costimulatory and coinhibitory signals to the CD28 family of receptors on T lymphocytes, the balance between which determines the ultimate immune response. Although B7-H4, a recently discovered member of the B7 family, is known to negatively regulate T cell immunity in autoimmunity and cancer, its role in solid organ allograft rejection and tolerance has not been established. Targeting the B7-H4 molecule by a blocking antibody or use of B7-H4(-/-) mice as recipients of fully MHC-mismatched cardiac allografts did not affect graft survival. However, B7-H4 blockade resulted in accelerated allograft rejection in CD28-deficient recipients. B7-1/B7-2-double-deficient recipients are truly independent of CD28/CTLA-4:B7 signals and usually accept MHC-mismatched heart allografts. Blockade of B7-H4 in these mice also precipitated rejection, demonstrating regulatory function of this molecule independent of an intact CD28/CTLA-4:B7 costimulatory pathway. Accelerated allograft rejection was always accompanied by increased frequencies of alloreactive IFN-γ-, IL-4- and Granzyme B-producing splenocytes. Finally, intact recipient, but not donor, B7-H4 is essential for prolongation of allograft survival by blocking CD28/CTLA4:B7 pathway using CTLA4-Ig. These data are the first to provide evidence of the regulatory effects of B7-H4 in alloimmune responses in a murine model of solid organ transplantation.

Ectopic B7-H4-Ig expression attenuates concanavalin A-induced hepatic injury

Previous studies demonstrate that both membrane B7-H4 and B7-H4-Ig fusion protein could inhibit T-cell responses. In the present study, we explored the potential effect of B7-H4-Ig on liver injury in a hepatitis mouse model induced by concanavalin A (ConA). A B7-H4-Ig construct was introduced into animals by the hydrodynamic gene delivery approach. It was found that ectopic expression of B7-H4-Ig could inhibit ConA-induced elevation of serum levels of ALT and AST, suppress liver necrosis and even mortality of mice. Furthermore, we observed that pretreatment of B7-H4-Ig dramatically decreased serum levels and the expression of mRNA for IL-2, IFN-gamma and IL-4, but increased IL-10 in ConA-treated mice. Our results suggest that B7-H4-Ig may protect animals from liver injury induced by ConA, which could be associated with reduced serum levels for IL-2, IFN-gamma and IL-4 as well as enhanced IL-10 production.