Circulating B7-H3(CD276) Elevations in Cerebrospinal Fluid and Plasma of Children with Bacterial Meningitis

The Impact of Laparoscopic Appendectomy and Open Appendectomy on B7-H3-Mediated Intrinsic Immune Response in Children with Acute Suppurative Appendicitis

Purpose

Surgery impairs immune function and increases postoperative complications. B7H3, a co-stimulatory molecule, plays a crucial role in immune regulation. The present study examined the impact of B7H3 on the postoperative immune response in children with acute suppurative appendicitis (ASA) by comparing preoperative and postoperative B7H3 levels in laparoscopic surgery (LA) and open appendectomy (OA).

Patients and Methods

198 pediatric ASA patients were enrolled. The researcher group performed LA, while the control group performed OA. Perioperative time, recovery time of gastrointestinal function, time to pass gas, length of incision, and length of hospitalization were compared in the perioperative period. Additionally, an ELISA assay was conducted to examine the levels of inflammatory factors and B7H3 and CD28. Short-term postoperative complications were also evaluated.

Results

Compared with the control group, the research group had a short operative time, gastrointestinal function recovery time, gas time, and hospitalization time. The short-term complication rate was significantly lower in the research group. More importantly, B7H3 and CD28 were insignificantly different preoperatively, but they were all reduced postoperatively. Moreover, the reduction was more pronounced in the research group. The same results were noted in inflammatory factors and immune markers, which were non-significant different preoperatively and were typically reduced postoperatively, particularly in the research group. Finally, postoperative B7H3 was positively correlated with both inflammatory factors and immune cell levels.

Conclusion

B7H3 was reduced in both postoperative periods, and the reduction was more pronounced in the LA group. B7H3 may be involved in postoperative recovery by modulating postoperative inflammation and immune responses.

Related Markers for the Precision Diagnosis of Complex Appendicitis in Children

Acute appendicitis is the most common surgical emergency in children. Despite the high incidence rate of appendicitis, it is sometimes misdiagnosed or missed. Complex appendicitis (CA) in children is characterized by a critical condition, several complications, and high mortality. Precision distinguishing between simple appendicitis and CA correctly is key to choosing appropriate treatment. A safe, cheap, rapid, extensive and accurate diagnostic marker of appendicitis will be of great significance for emergency general surgeons to treat suspected CA. Many studies have investigated possible diagnostic markers for the diagnosis of CA in children. In this study, studies related to CA in children in recent years are summarized, and the related markers and scoring system for the diagnosis of CA in children are summarized.

sB7H3 in Children with Acute Appendicitis: Its Diagnostic Value and Association with Histological Findings

Background

Several efforts have been made to find out a valuable marker to assist the diagnosis and differentiation of gangrenous/perforated appendicitis. We aimed to determine the diagnostic capacity of soluble B7H3 (sB7H3) in acute appendicitis (AA) and its accuracy as a predictor of the severity of appendicitis.

Methods

182 children were allocated into four groups as follows: control group (CG, 90), simple appendicitis (SA, 12), purulent appendicitis (PA, 49), and gangrenous appendicitis (GA, 31). Prior to appendectomy, blood was collected and sent for analysis of routine examination and cytokines (sB7H3 and TNF-α). We compared values of all measured parameters according to histological findings. Furthermore, we assigned AA patients into the nonperforated appendicitis group and the perforated appendicitis group. The diagnostic effects of significant markers were assessed by ROC curves.

Results

Only the levels of CRP, FIB, and sB7H3 had a remarkable rising trend in AA-based groups, while differences in the levels of CRP and FIB between simple appendicitis and purulent appendicitis were not statistically significant. In addition, sB7H3 was found as the only marker in children with AA, which was markedly associated with the degree of histological findings of the appendix. Furthermore, sB7H3 had a high diagnostic value in predicting AA and complex appendicitis (PA+GA) in children. However, the diagnostic performance of sB7H3 for distinguishing PA from GA was not remarkable. Additionally, only the levels of CRP and sB7H3 were statistically different between the nonperforated appendicitis group and the perforated appendicitis group. The diagnostic performance of CRP and sB7H3 could not merely predict perforation of AA in children; however, the diagnostic performance was improved after combination.

Conclusions

sB7H3 could be used as a valuable marker to predict the presence of AA and complex AA in children. However, the diagnostic value of sB7H3 to predict gangrenous/perforated appendicitis was not found to be remarkable. The combination of sB7H3 and CRP might improve the prediction of perforated appendicitis.

B7-H3: A promising therapeutic target for autoimmune diseases

B7-H3 as a newly identified costimulatory molecule that belongs to B7 ligand family, is broadly expressed in both lymphoid and non-lymphoid tissues. The overexpression of B7-H3 has been verified to be correlated with the poor prognosis and poor clinical outcome of several human cancers. In recent years, researchers reveal that B7-H3 is involved in the pathogenesis of various autoimmune diseases, such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), multiple sclerosis (MS), Sjögren's syndrome (SS), ankylosing spondylitis (AS), etc. In this review, we will discuss the biological function of B7-H3 and summarize the progress made over past years regarding its role in the occurrence and development of autoimmune diseases. The insights gained from these findings could serve as the foundation for future therapies of these diseases.

Prediction of Bronchopulmonary Dysplasia in Preterm Infants Using Postnatal Risk Factors

Objective: To identify postnatal risk factors for bronchopulmonary dysplasia (BPD) development in preterm infants with gestational age ≤32 weeks. Methods: Seventy-two preterm infants(30 with BPD and 42 non-BPD controls) admitted in the neonatal intensive care unit (NICU) of the Children's Hospital of Soochow University during 2017 were enrolled in this prospective longitudinal study. Perinatal clinical data, a neonatal critical illness score (NCIS), different soluble B7-H3(sB7-H3), and interleukin-18 (IL-18) levels by days after birth were collected. An early predictive model for BPD development was established based on clinical data using multiple logistic regression analysis. And the sensitivity and specificity of the model were assesed by ROC curve. Results: Electrolyte disturbances, hemodynamically significant patent ductus arteriosus (hs-PDA), and the age that infants achieved 120 kcal/kg.d via enteral feeding ≥40 days after birth were found to be associated with the BPD pathogenesis. Serum sB7-H3, IL-18, and NCIS were significantly higher in the BPD group compared to the non-BPD group (p < 0.05). BPD group had significantly lower enteral fluid and caloric intake compared to the non-BPD group at 1, 7, 14, and 28 days after birth. The risk factors were analyzed by multiple logistic regression and a predictive model of a combination of sB7-H3 (day 7), IL-18 (day 14), NCIS, and clinical risk factors was evaluated via ROC curve with an area under the curve (AUC) of 0.960 having sensitivity of 86.7% and a specificity of 97.6%, respectively. Conclusion: The causes of BPD are multifactorial postnatal risk factors. And the combination of sB7-H3 (day 7), IL-18 (day 14), NCIS, and clinical risk factors (electrolyte disturbances, hs-PDA, and the age that infants achieved 120 kcal/kg.d via enteral feeding ≥40 days after birth) might be served as an optimal predictive model for the occurrence of BPD.

Coinhibitory Pathways in the B7-CD28 Ligand-Receptor Family

Immune responses need to be controlled for optimal protective immunity and tolerance. Coinhibitory pathways in the B7-CD28 family provide critical inhibitory signals that regulate immune homeostasis and defense and protect tissue integrity. These coinhibitory signals limit the strength and duration of immune responses, thereby curbing immune-mediated tissue damage, regulating resolution of inflammation, and maintaining tolerance to prevent autoimmunity. Tumors and microbes that cause chronic infections can exploit these coinhibitory pathways to establish an immunosuppressive microenvironment, hindering their eradication. Advances in understanding T cell coinhibitory pathways have stimulated a new era of immunotherapy with effective drugs to treat cancer, autoimmune and infectious diseases, and transplant rejection. In this review we discuss the current knowledge of the mechanisms underlying the coinhibitory functions of pathways in the B7-CD28 family, the diverse functional consequences of these inhibitory signals on immune responses, and the overlapping and unique functions of these key immunoregulatory pathways.

B7-H3 Augments Inflammatory Responses and Exacerbates Brain Damage via Amplifying NF-κB p65 and MAPK p38 Activation during Experimental Pneumococcal Meningitis

The costimulatory protein B7-H3 has been shown to play a contributory role in the development and progression of experimental pneumococcal meningitis by augmentation of the innate immunity-associated inflammatory response via a TLR2-dependent manner. This study aimed to clarify the component(s) of TLR2-mediated signal transduction pathways responsible for B7-H3-augmented inflammatory response and subsequent brain damage during experimental pneumococcal meningitis. Administration of B7-H3 did not augment expression of TLR2 and other TLR2 upstream components, but led to an enhanced formation of MyD88-IRAK immunocomplex in the brain of S. pneumoniae-infected mice. Furthermore, B7-H3 substantially augmented S. pneumoniae-induced activation of TLR2 downstream NF-κB p65 and MAPK p38 pathways in the brain of S. pneumoniae-infected mice. Notably, blockage of NF-κB p65 and/or MAPK p38 with their specific inhibitors strongly attenuated B7-H3-amplified inflammatory response with significantly reduced proinflammatory cytokine and chemokine production, and markedly ameliorated B7-H3-exacerbated disruption of blood-brain barrier and severity of disease status in S. pneumoniae-infected mice. These results indicate that targeting NF-κB p65 and/or MAPK p38 may represent a promising therapeutic option for amelioration of overwhelming inflammatory response-associated brain injury frequently observed during pneumococcal meningitis.

B7H3 ameliorates LPS-induced acute lung injury via attenuation of neutrophil migration and infiltration

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are characterized by an excessive inflammatory response within the lungs and severely impaired gas exchange resulting from alveolar-capillary barrier disruption and pulmonary edema. The costimulatory protein B7H3 functions as both a costimulator and coinhibitor to regulate the adaptive and innate immune response, thus participating in the development of microbial sepsis and pneumococcal meningitis. However, it is unclear whether B7H3 exerts a beneficial or detrimental role during ALI. In the present study we examined the impact of B7H3 on pulmonary inflammatory response, polymorphonuclear neutrophil (PMN) influx, and lung tissue damage in a murine model of lipopolysaccharide (LPS)-induced direct ALI. Treatment with B7H3 protected mice against LPS-induced ALI, with significantly attenuated pulmonary PMN infiltration, decreased lung myeloperoxidase (MPO) activity, reduced bronchoalveolar lavage fluid (BALF) protein content, and ameliorated lung pathological changes. In addition, B7H3 significantly diminished LPS-stimulated PMN chemoattractant CXCL2 production by inhibiting NF-κB p65 phosphorylation, and substantially attenuated LPS-induced PMN chemotaxis and transendothelial migration by down-regulating CXCR2 and Mac-1 expression. These results demonstrate that B7H3 substantially ameliorates LPS-induced ALI and this protection afforded by B7H3 is predominantly associated with its inhibitory effect on pulmonary PMN migration and infiltration.

Anti-B7-H3 monoclonal antibody ameliorates the damage of acute experimental pancreatitis by attenuating the inflammatory response

B7-H3, a recently discovered B7 family member, is documented as a regulator in the inflammatory response as well as T cell-mediated immune responses. In this paper, we find that patients with acute pancreatitis revealed overwhelming levels of serum soluble B7-H3 (sB7-H3) associated with the clinical outcomes. Furthermore, B7-H3 protein was marked increased in l-arginine-induced acute experimental pancreatitis. Anti-B7-H3 monoclonal antibody treatment attenuated the proinflammatory cytokine production, downregulated the activation of the NF-κB signaling pathway, and ameliorated the pancreas disruption in l-arginine-induced pancreatitis. In addition, although l-arginine alone failed to induce the production of proinflammatory cytokine and anti-B7-H3 mAb had no effect on the proinflammatory cytokine production of acinar cells, administration of anti-B7-H3 mAb in the coculture model of acinar cells and macrophages stimulated by l-arginine displayed the similar effects. On the whole, B7-H3 participates in the development of acute pancreatitis, and anti-B7-H3 monoclonal antibody ameliorates severity of acute experimental pancreatitis via attenuation of the inflammatory response.

B7 homolog 3 aggravates brain injury in a murine model of Streptococcus pneumoniae-induced meningitis

Despite the application of antibiotics, Streptococcus pneumoniae (SP)-induced meningitis continues to be a life-threatening disease with a high fatality rate and an elevated risk of serious neurological sequelae, particularly in developing countries. In this study, the contribution of the co-stimulatory molecule B7 homolog 3 (B7-H3) to the pathogenesis of experimental SP-induced meningitis was investigated. Mice were challenged with the intracerebroventricular injection of serotype 3 SP with or without B7-H3. The clinical status of mice with SP-induced meningitis was examined by body weight loss and spontaneous motor activity with neurological scoring. Coronal brain sections were analyzed by counting Nissl-positive neurons and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells. Protein expression of neuron-specific enolase (NSE) and S100B in brain tissues was examined with immunohistochemical staining. All experiments were performed in a randomized and blinded setting. By the intracerebroventricular injection of SP suspension, a murine model of pneumococcal meningitis was successfully established. In this SP-induced meningitis model, B7-H3 deteriorated the clinical status, as manifested by a decreased neurological score and increased body weight loss. Following the B7-H3 challenge, the number of Nissl-positive cells decreased and TUNEL-stained positive cells increased in the brain tissues of mice with SP meningitis, which demonstrates the enhancement of neuronal necrosis and apoptosis, respectively. Protein expression of NSE was decreased, while that of S100B was increased. These in vivo findings indicate that B7-H3 aggravates brain injury during the pathological process of experimental SP-induced meningitis.

B7-H3 and B7-H1 expression in cerebral spinal fluid and tumor tissue correlates with the malignancy grade of glioma patients

The B7 family consists of activating and inhibitory molecules that regulate immune responses. Recent research demonstrated the roles of soluble B7-H3 (sB7-H3) and soluble B7-H1 (sB7-H1) in the blood serum of various tumors; however, none of these studies investigated the expression of these proteins in the cerebral spinal fluid (CSF) and blood serum of patients with glioma. The aim of the present study was to investigate the expression of B7-H3 and B7-H1 in the CSF, blood serum and tissues of patients with glioma and their correlation with clinicopathological data. Between January 2012 and November 2012, samples were obtained from 78 patients with glioma, four CSF samples were obtained from patients with a moderate traumatic brain injury, four brain tissue samples were obtained from patients with a traumatic brain injury and 40 blood serum samples were obtained from healthy individuals. The expression of B7-H3 and B7-H1 in the CSF, blood serum and tumor samples of the patients with high-grade glioma was found to be higher than that in the patients with low-grade glioma. However, no significant differences in sB7-H3 and sB7-H1 expression were observed in the blood serum of the patients with glioma compared with the healthy control subjects. In addition, the expression of sB7-H3 and sB7-H1 in the CSF of the patients with glioma was higher than that in the CSF of the patients with a moderate traumatic brain injury. Furthermore, in the patients with glioma, B7-H3 and B7-H1 expression in the CSF and tumor tissue, although not in the blood serum, correlated with the glioma grade.

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.

Soluble B7-H3 elevations in hospitalized children with Mycoplasma pneumoniae pneumonia

The purpose of this study is to explore the associations between soluble B7-H3 (sB7-H3) and cytokines, clinical characteristics and laboratory findings. Thirty-two children with Mycoplasma pneumoniae pneumonia diagnosed by both positive serology and PCR were admitted to Children's Hospital affiliated to Soochow University. These children were enrolled and evaluated from May 2012 through September 2012. Soluble B7-H3 level and cytokines (tumor necrosis factor-α (TNF-α), interferon-γ, interleukin (IL)-4, IL-10) were determined by enzyme-linked immunosorbent assay technique. Meanwhile, clinical parameters including laboratory findings were obtained. Soluble B7-H3 level was significantly increased in patients with M. pneumoniae pneumonia compared with the levels of sB7-H3 in control subjects (4.94 ± 2.69 vs. 3.42 ± 1.48, ng/mL; P = 0.032). Furthermore, level of sB7-H3 was correlated with TNF-α level in plasma in patients with M. pneumoniae pneumonia (rp = 0.667; P < 0.001) as well as level of sB7-H3 in M. pneumoniae pneumonia subjects was also correlated with duration of symptoms (rp = 0.607; P < 0.001), percentage of neutrophil cells (rp = 0.657; P < 0.001), and C-reactive protein level (rs = 0.445; P = 0.011). Level of sB7-H3 was decreased after treatment (6.08 ± 3.07 vs. 3.55 ± 1.58, ng/mL; P = 0.019). Soluble B7-H3 maybe plays an important role in immunopathogenesis of M. pneumoniae pneumonia, especially for increasing TNF-α concentration and activation neutrophils.

Emerging Co-signaling Networks in T Cell Immune Regulation

Co-signaling molecules are surface glycoproteins that positively or negatively regulate the T cell response to antigen. Co-signaling ligands and receptors crosstalk between the surfaces of antigen-presenting cells (APCs) and T cells, and modulate the ultimate magnitude and quality of T cell receptor (TCR) signaling. In the past 10 years, the field of co-signaling research has been advanced by the understanding of underlying mechanisms of the immune modulation led by newly identified co-signaling molecules and the successful preclinical and clinical trials targeting co-inhibitory molecules called immune checkpoints in the treatment of autoimmune diseases and cancers. In this review, we briefly describe the characteristics of well-known B7 co-signaling family members regarding the expression, functions and therapeutic implications and to introduce newly identified B7 members such as B7-H5, B7-H6, and B7-H7.

Induction of B7-H6, a ligand for the natural killer cell-activating receptor NKp30, in inflammatory conditions

B7-H6, a member of the B7 family of immunoreceptors, is as a cell-surface ligand for the NKp30-activating receptor expressed on natural killer cells. B7-H6 is not detected in normal human tissues at steady state but is expressed on tumor cells. However, whether B7-H6 can be expressed in other conditions remains unknown. We analyzed here the pathways that lead to the expression of B7-H6 in nontransformed cells. In vitro, B7-H6 was induced at the surface of CD14(+)CD16(+) proinflammatory monocytes and neutrophils upon stimulation by ligands of Toll-like receptors or proinflammatory cytokines such as interleukin-1β and tumor necrosis factor α. In these conditions, a soluble form of B7-H6 (sB7-H6) was also produced by activated monocytes and neutrophils. In vivo, B7-H6 was expressed on circulating proinflammatory CD14(+)CD16(+) monocytes in a group of patients in sepsis conditions, and was linked to an increased mortality. sB7-H6 was selectively detected in the sera of patients with gram-negative sepsis and was associated with membrane vesicles that co-sedimented with the exosomal fraction. These findings reveal that B7-H6 is not only implicated in tumor immunosurveillance but also participates in the inflammatory response in infectious conditions.

A novel monoclonal antibody against mouse B7-H3 developed in rats

B7-H3, a novel member of the B7 superfamily, plays a critical role during T cell activation; its functions are still unclear. In this study we obtained a novel anti-mouse B7-H3 monoclonal antibody (MAb) and characterized its biological functions. Our results demonstrated that this MAb could be used for flow cytometry and Western blot and immunohistochemistry analyses, suggesting that the performance of this MAb is much better than a commercial MAb (M3.2D7). Furthermore, data showed different expression profiles of mouse B7-H3 on various immune cells. We further showed that mouse B7-H3 protein was not expressed on normal tissues except for bladder epithelial cells using this MAb. Interestingly, the MAb could stimulate the proliferation and cytokine secretion of T cells. Taken together, this MAb might be of great value for further investigation of B7-H3 molecule.

Effects of B7-H3 on the inflammatory response and expression of MMP-9 in mice with pneumococcal meningitis

B7-H3, a new member of the B7 superfamily, plays a key role in the regulation of T cell-mediated immune responses. Our previous work showed that B7-H3 strongly augmented both LPS- and bacterial lipoprotein-induced NF-κB activation and inflammatory response, and soluble B7-H3 was elevated in CSF and plasma of patients with bacterial meningitis. MMP-9 has been implicated in blood-brain barrier disruption, inflammation, and vasculitis during the pathogenesis of bacterial meningitis. In this study, we report that in a murine model of pneumococcal meningitis, B7-H3 treatment enhances inflammatory response in the meninges, upregulates MMP-9 expression in cerebral parenchyma, and deteriorates clinical disease status indicated by weight loss and impaired movement ability. In vitro results showed that B7-H3 augmented MMP-9 secretion from Streptococcus pneumoniae-stimulated microglia cells. Thus, our data indicate that B7-H3 contributes to the development of pneumococcal meningitis by exaggerating inflammatory responses and upregulating MMP-9 activity in CNS, which ultimately lead to neuronal injury.

B7-H3 participates in the development of experimental pneumococcal meningitis by augmentation of the inflammatory response via a TLR2-dependent mechanism

In addition to a well-documented role in regulating T cell-mediated immune responses, B7-H3, a newly discovered member of the B7 superfamily, has been recently identified as a costimulator in the innate immunity-mediated inflammatory response. In this study, we further report that B7-H3 participates in the development of pneumococcal meningitis in a murine model. Exogenous administration of B7-H3 strongly amplified the inflammatory response, exacerbated blood-brain barrier disruption, and aggravated the clinical disease status in Streptococcus pneumoniae-infected C3H/HeN wild-type mice. Consistent with the in vivo findings, B7-H3 substantially augmented proinflammatory cytokine and chemokine production, upregulated NF-κB p65 and MAPK p38 phosphorylation, and enhanced the nuclear transactivation of NF-κB p65 at both TNF-α and IL-6 promoters in S. pneumoniae-stimulated primary murine microglia cells. These B7-H3-associated in vitro and in vivo effects appeared to be dependent on TLR2 signaling, as B7-H3 almost completely lost its amplifying actions in both TLR2-deficient microglial cells and TLR2-deficient mice. Furthermore, administration of the anti-B7-H3 mAb (MIH35) attenuated the inflammatory response and ameliorated blood-brain barrier disruption in S. pneumoniae-infected wild-type mice. Collectively, our results indicate that B7-H3 plays a contributory role in the development of S. pneumoniae infection-induced bacterial meningitis.

Costimulatory protein 4IgB7H3 drives the malignant phenotype of glioblastoma by mediating immune escape and invasiveness

PURPOSE

Recent work points out a role of B7H3, a member of the B7-family of costimulatory proteins, in conveying immunosuppression and enforced invasiveness in a variety of tumor entities. Glioblastoma is armed with effective immunosuppressive properties resulting in an impaired recognition and ineffective attack of tumor cells by the immune system. In addition, extensive and diffuse invasion of tumor cells into the surrounding brain tissue limits the efficacy of local therapies. Here, 4IgB7H3 is assessed as diagnostic and therapeutic target for glioblastoma.

EXPERIMENTAL DESIGN

To characterize B7H3 in glioblastoma, we conduct analyses not only in glioma cell lines and glioma-initiating cells but also in human glioma tissue specimens.

RESULTS

B7H3 expression by tumor and endothelial cells correlates with the grade of malignancy in gliomas and with poor survival. Both soluble 4IgB7H3 in the supernatant of glioma cells and cell-bound 4IgB7H3 are functional and suppress natural killer cell-mediated tumor cell lysis. Gene silencing showed that membrane and soluble 4IgB7H3 convey a proinvasive phenotype in glioma cells and glioma-initiating cells in vitro. These proinvasive and immunosuppressive properties were confirmed in vivo by xenografted 4IgB7H3 gene silenced glioma-initiating cells, which invaded significantly less into the surrounding brain tissue in an orthotopic model and by subcutaneously injected LN-229 cells, which were more susceptible to natural killer cell-mediated cytotoxicity than unsilenced control cells.

CONCLUSIONS

Because of its immunosuppressive and proinvasive function, 4IgB7H3 may serve as a therapeutic target in the treatment of glioblastoma.

Origination of new immunological functions in the costimulatory molecule B7-H3: the role of exon duplication in evolution of the immune system

B7-H3, a recently identified B7 family member, has different isoforms in human and mouse. Mouse B7-H3 gene has only one isoform (2IgB7-H3) with two Ig-like domains, whereas human B7-H3 has two isoforms (2IgB7-H3 and 4IgB7-H3). In this study a systematic genomic survey across various species from teleost fishes to mammals revealed that 4IgB7-H3 isoform also appeared in pigs, guinea pigs, cows, dogs, African elephants, pandas, megabats and higher primate animals, which resulted from tandem exon duplication. Further sequence analysis indicated that this duplication generated a new conserved region in the first IgC domain, which might disable 4IgB7-H3 from releasing soluble form, while 2IgB7-H3 presented both membrane and soluble forms. Through three-dimensional (3D) structure modeling and fusion-protein binding assays, we discovered that the duplicated isoform had a different structure and might bind to another potential receptor on activated T cells. In T cell proliferation assay, human 2IgB7-H3 (h2IgB7-H3) and mouse B7-H3 (mB7-H3) both increased T cell proliferation and IL-2, IFN-γ production, whereas human 4IgB7-H3 (h4IgB7-H3) reduced cytokine production and T cell proliferation compared to control. Furthermore, both h2IgB7-H3 and mB7-H3 upregulated the function of lipopolysacharide (LPS)-activated monocyte in vitro. Taken together, our data implied that during the evolution of vertebrates, B7-H3 exon duplication contributed to the generation of a new 4IgB7-H3 isoform in many mammalian species, which have carried out distinct functions in the immune responses.

B7-H3 augments the inflammatory response and is associated with human sepsis

B7-H3, a new member of the B7 superfamily, acts as both a T cell costimulator and coinhibitor, and thus plays a key role in the regulation of T cell-mediated immune responses. However, it is unclear whether B7-H3 is involved in the innate immune monocyte/macrophage-mediated inflammatory response. In this paper, we show that, although B7-H3 alone failed to stimulate proinflammatory cytokine release from murine macrophages, it strongly augmented both LPS- and bacterial lipoprotein-induced NF-kappaB activation and inflammatory response. This occurred in both a TLR4- and TLR2-dependent manner. Blockage of B7-H3 in vivo attenuated LPS-induced proinflammatory cytokine release and endotoxic shock-related lethality. Furthermore, we found that patients diagnosed with sepsis, in contrast to healthy individuals, exhibited significant levels of raised plasma soluble B7-H3 (sB7-H3) and that this level correlated with the clinical outcome and levels of plasma TNF-alpha and IL-6. In addition, a putative receptor for B7-H3 was detected on monocytes and peritoneal macrophages from septic patients but not on monocytes from healthy donors. Stimulation of human monocytes with LPS and inflammatory cytokines led to a substantial release of sB7-H3. Taken together, our data indicate that significantly elevated plasma sB7-H3 in septic patients may predict a poor outcome. Furthermore, we demonstrate that B7-H3 functions as a costimulator of innate immunity by augmenting proinflammatory cytokine release from bacterial cell wall product-stimulated monocytes/macrophages and may contribute positively to the development of sepsis.