Fumihiko Tsushima

B7-H1/CD80 interaction is required for the induction and maintenance of peripheral T-cell tolerance.

T-cell tolerance is the central program that prevents harmful immune responses against self-antigens, in which inhibitory PD-1 signal given by B7-H1 interaction plays an important role. Recent studies demonstrated that B7-H1 binds CD80 besides PD-1, and B7-H1/CD80 interaction also delivers inhibitory signals in T cells. However, a role of B7-H1/CD80 signals in regulation of T-cell tolerance has yet to be explored. We report here that attenuation of B7-H1/CD80 signals by treatment with anti-B7-H1 monoclonal antibody, which specifically blocks B7-H1/CD80 but not B7-H1/PD-1, enhanced T-cell expansion and prevented T-cell anergy induction. In addition, B7-H1/CD80 blockade restored Ag responsiveness in the previously anergized T cells. Experiments using B7-H1 or CD80-deficient T cells indicated that an inhibitory signal through CD80, but not B7-H1, on T cells is responsible in part for these effects. Consistently, CD80 expression was detected on anergic T cells and further up-regulated when they were re-exposed to the antigen (Ag). Finally, blockade of B7-H1/CD80 interaction prevented oral tolerance induction and restored T-cell responsiveness to Ag previously tolerized by oral administration. Taken together, our findings demonstrate that the B7-H1/CD80 pathway is a crucial regulator in the induction and maintenance of T-cell tolerance.

B7-DC Regulates Asthmatic Response by an IFN-γ-Dependent Mechanism

B7-H1 (PD-L1) and B7-DC (PD-L2) are the ligands for programmed death-1 (PD-1), which is a member of the CD28/CTLA-4 family and has been implicated in peripheral tolerance. We investigated the roles of B7-H1 and B7-DC in a murine OVA-induced allergic asthma model. B7-H1 was constitutively expressed on dendritic cells, macrophages, B cells, and T cells in the lungs of naive mice, and its expression could be dramatically increased after allergen challenge. In contrast, B7-DC expression was scarcely expressed on dendritic cells in naive mice, but was up-regulated after allergen challenge, although the up-regulation of B7-DC expression on macrophages was minimal. Treatment of mice with anti-B7-DC mAb at the time of allergen challenge, but not at the time of sensitization, significantly increased their airway hyper-reactivity and eosinophilia. Such treatment also resulted in the increased production of IL-5 and IL-13, and decreased IFN-γ production in the lungs and draining lymph node cells. These changes were diminished when mice were depleted of IFN-γ by anti-IFN-γ mAb pretreatment. Interestingly, treatment with anti-B7-H1 or anti-PD-1 mAb did not significantly affect the asthmatic response. These results suggest a unique role for B7-DC in the regulation of asthmatic response through an IFN-γ-dependent, but PD-1-independent, mechanism.

Involvement of inducible costimulator-B7 homologous protein costimulatory pathway in murine lupus nephritis.

Inducible costimulator (ICOS)-B7 homologous protein (B7h) is a new member of the CD28-B7 family of costimulatory molecules that regulates T cell-dependent humoral immune responses. In this study, we examined the involvement of this costimulatory pathway in the development and progression of lupus in NZB/W F1 mice. Expression of ICOS on T cells was enhanced with disease progression, whereas B7h expression on B cells was down-regulated. Administration of anti-B7h mAb before the onset of renal disease significantly delayed the onset of proteinuria and prolonged survival. Blockade of B7h effectively inhibited all subclasses of IgG autoantibody production and accumulation of both Th1 and Th2 cells. Hypercellularity and deposition of IgG and C3 in glomeruli were significantly reduced. B7h blockade after the onset of proteinuria prevented the disease progression and improved the renal pathology. Our results demonstrated the involvement of the ICOS-B7h costimulatory pathway in the pathogenesis of lupus nephritis, and the blockade of this pathway may be beneficial for the treatment of human systemic lupus erythematosus.

Preferential contribution of B7‐H1 to programmed death‐1‐mediated regulation of hapten‐specific allergic inflammatory responses

Programmed death‐1 (PD‐1) and its ligands, B7‐H1/PD‐L1 and B7‐DC/PD‐L2, are new CD28‐B7 family members that may be involved in the regulation of immune responses. We examined the roles of these molecules in mouse hapten‐induced contact hypersensitivity (CH). Administration of anti‐PD‐1 mAb at sensitization significantly enhanced and prolonged ear swelling. Treatment with anti‐B7‐H1 mAb, but not anti‐B7‐DC mAb, also enhanced CH reactions. The anti‐PD‐1 mAb treatment at sensitization significantly increased the T cell number of draining lymph nodes (DLN). B7‐H1 was induced on activated T cells and antigen‐presenting cells (APC) in the skin and the DLN, whereas B7‐DC expression was restricted to dendritic cells (DC) in the dermis and the DLN. A particular subset of DC, B7‐H1+B7‐DC–CD86low, was found in sensitized DLN. The blockade of B7‐H1, but not B7‐DC, dramatically enhanced the initial T cell proliferative responses against hapten‐pulsed DLN APC, suggesting the preferential contribution of B7‐H1 to the T cell‐APC interaction. Our results demonstrate the regulatory role of PD‐1 and the differential roles of B7‐H1 and B7‐DC in hapten‐induced immune responses. The PD‐1‐B7‐H1 pathway may play a unique role in regulating inflammatory responses.

Blockade of the Interaction Between PD-1 and PD-L1 Accelerates Graft Arterial Disease in Cardiac Allografts

Background—Programmed death-1 (PD-1), a member of the CD28 family, has been identified. PD-1 is involved in the negative regulation of some immune responses. We evaluated the role of PD-ligand 1 (PD-L1) in graft arterial disease (GAD) of cardiac allografts and in smooth muscle cells (SMCs). Methods and Results—C57BL/6 murine hearts were transplanted into B6.C-H2KhEg mice for examination of GAD. PD-L1 was expressed in SMCs of the thickened intima in the graft coronary arteries, and administration of anti–PD-L1 monoclonal antibody (mAb) enhanced the progression of GAD (luminal occlusion: 55±5.0% versus 9.8±4.3%, P<0.05). The expressions of interferon γ (IFN-γ) and tumor necrosis factor α of cardiac allografts were upregulated in response to anti–PD-L1 mAb treatment. In vitro, PD-L1 expression was induced in SMCs in response to IFN-γ stimulation. Sensitized splenocytes increased SMC proliferation, and anti–PD-L1 mAb in combination with IFN-γ stimulation increased this proliferation. Conclusions—The PD-L1 pathway regulates both the proliferation of SMCs and GAD. Thus, control of this interaction is a promising strategy for suppression of GAD.

Immunoregulatory Molecule B7-H1 (CD274) Contributes to Skin Carcinogenesis

B7-H1 (CD274), a member of the B7 family of coinhibitory molecules, is often induced in human tumors and its expression is closely correlated with a poor prognosis or higher malignancy grade. Tumor-associated B7-H1 is implicated in mechanisms of immune escape. Under inflammatory conditions, B7-H1 is also inducible in normal epithelial cells, but little is known about its involvement in the conversion of normal cells to tumor cells. We recently found that skin-specific expression of B7-H1 accelerates chemically induced carcinogenesis of squamous cell carcinoma (SCC), despite impaired skin inflammatory responses, in B7-H1 transgenic (B7-H1tg) mice. B7-H1tg-derived keratinocytes (KC) and SCCs exhibited a marked reduction of E-cadherin, and B7-H1tg-originated SCCs showed elevated expression of the transcription factors Slug and Twist, suggesting that B7-H1 overexpression in KCs promotes the epithelial-mesenchymal transition and accelerates carcinogenesis. This review discusses the diverse functions of B7-H1 in carcinogenesis and cancer progression, and considers future directions for developing cancer therapy targeting B7-H1.

Keratinocyte-Associated B7-H1 Directly Regulates Cutaneous Effector CD8+ T Cell Responses

Keratinocytes (KCs) may play important roles for maintenance of peripheral tolerance in the upper layers of the skin. Coinhibitory signals mediated via the programmed death (PD)-1 and its ligand B7-H1 (PD-L1/CD274) are crucial for the downregulation of T cell immune responses and for the maintenance of peripheral tolerance. In this study, to investigate the role of KC-expressed B7-H1 in the regulation of T cell immune responses, we generated transgenic (tg) mice overexpressing B7-H1 under the control of keratin 14 (K14) promoter (K14-B7-H1 tg). K14-B7-H1 tg mice displayed impaired contact hypersensitivity (CH) responses to primary and secondary hapten challenges. The K14-B7-H1 tg mice did not exhibit substantial impairment of cutaneous dendritic cell migration after sensitization and of hapten-specific proliferation and IFN-γ production of CD4+ and CD8+ T cells in the draining lymph nodes, suggesting that overexpression of B7-H1 on KCs did not affect the induction phase of the CH response. The systemic or s.c. injection of hapten-sensitized T cells into the K14-B7-H1 tg mice did not efficiently induce the CH response. IFN-γ expression and apoptosis of KCs in the challenged ears were impaired in K14-B7-H1 tg mice. IFN-γ production by presensitized CD8+ T cells stimulated with hapten-pulsed KCs was markedly impaired for the KCs obtained from the K14-B7-H1 tg mice but was restored by the addition of an anti–B7-H1 mAb. These results suggest that KC-associated B7-H1 directly downregulates the effector function of CD8+ T cells by associating with PD-1 at local inflammatory sites and that it plays a role in peripheral T cell tolerance against exogenous Ags.

Recurrence patterns of oral leukoplakia after curative surgical resection: important factors that predict the risk of recurrence and malignancy.

BACKGROUND Oral leukoplakia can be treated using a variety of treatment procedures; however, the lesions recur in many cases irrespective of the treatment procedure used. The rate of recurrence was from 7.7% to 38.1%. This study aims to identify the important factors that can lower the risk of recurrence of oral leukoplakia treated by curative surgical resection. METHODS The clinical records of 52 patients with oral leukoplakia (53 lesions) who underwent curative surgical resection between 2004 and 2009 were retrospectively analyzed for the rate of recurrence, clinical outcome, epithelial dysplasia, lesion location, and resection margins. RESULTS The recurrence rate following curative surgical resection was 15.1%, with the most common site being the gingiva. Malignant transformation occurred in a single patient (1.9%). Minimal resection margins (<3 mm) were observed in many patients with recurrent disease, and recurrence was more likely in cases with positive margins (epithelial abnormalities at the resection margins) than in those with negative margins. There was no significant association between recurrence and the degree of epithelial dysplasia. CONCLUSIONS Our data suggest that surgical resection of oral leukoplakia is curative only if all areas of epithelial abnormalities are identified and resected. Moreover, an adequate resection margin may reduce the risk of recurrence.

Long-term outcome of non-surgical treatment in patients with oral leukoplakia

UNLABELLED The standard treatments for oral leukoplakia range from careful observation to complete resection. No surgical intervention is chosen for several supposable reasons. Surgical treatment and no surgical treatment for oral leukoplakia have no defined basis for comparisons, and few studies have reported on the long-term outcomes of oral leukoplakia without surgery. OBJECTIVES This study aimed to identify the important factors using a long-term wait-and-see policy in patients with oral leukoplakia. MATERIALS AND METHODS In total, 237 lesions from 218 patients selected for non-surgical therapy between 2001 and 2010 were analyzed. On the basis of long-term follow-up data, lesions were classified as unchanged, reduced, disappeared, expanded, and malignantly transformed. RESULTS In total, 135 (57.0%) lesions remained unchanged, 30 (12.7%) lesions were characterized by a reduction in size or clinical severity, and 44 (18.6%) lesions had disappeared. Another 17 (7.2%) lesions resulted in spread or clinical deterioration, and 11 (4.6%) lesions developed oral squamous cell carcinoma. CONCLUSIONS We demonstrated a cumulative malignant transformation rate of 11.6% in 10years without resection. The lesions that were nonhomogeneous, and higher degree of epithelial dysplasia, located on the tongue were likely to progress into cancer. In addition, 32.5% of lesions without surgical treatment were reduced or disappeared. There is a possibility that removal of considerable irritation for a long time contributes to the treatment of this disease. The development of appropriate treatments for oral leukoplakia is required, which will enable successful differentiation between surgical and observation cases.

Leucocyte-associated immunoglobulin-like receptor-1 is an inhibitory regulator of contact hypersensitivity

Leucocyte‐associated immunoglobulin‐like receptor‐1 (LAIR‐1) is a membrane receptor of the immunoglobulin (Ig) superfamily that is expressed on most types of haematopoietic cells, and delivers inhibitory signals through interacting with collagens. In order to elucidate the immunological functions of LAIR‐1 in vivo, we established transgenic mice expressing a chimeric protein composed of the extracellular domain of LAIR‐1 fused with an Ig tag (LAIR‐1–Ig), which acts as a decoy by competing with endogenous LAIR‐1. The transgenic mice showed an increased susceptibility for development of contact hypersensitivity (CHS), an experimental model of allergic contact dermatitis, in association with enhanced hapten‐specific T‐cell responses. When T cells from the hapten‐sensitized donor mice were transferred into non‐sensitized recipients, treatment of either donor mice or recipient mice with LAIR‐1–Ig protein accelerated CHS, suggesting a potentially negative role of LAIR‐1 in both the sensitization and the elicitation of hapten‐reactive T cells. In vitro assays revealed that LAIR‐1 decreased the production of interleukin‐6 and interleukin‐12 in dendritic cells, and inhibited the proliferation and cytokine production of naïve and memory T cells along with G0/G1 cell cycle arrest. Collectively, our findings suggest that LAIR‐1 plays a crucial inhibitory role in CHS by regulating antigen‐presenting cell and T‐cell functions.