Luman Wang

TLR1/TLR2 agonist induces tumor regression by reciprocal modulation of effector and regulatory T cells.

Using TLR agonists in cancer treatment can have either beneficial or detrimental effects. Therefore, it is important to determine their effect on the tumor growth and understand the underlying mechanisms in animal tumor models. In this study, we report a general immunotherapeutic activity of a synthetic bacterial lipoprotein (BLP), a TLR1/TLR2 agonist, on established lung carcinoma, leukemia, and melanoma in mice. Systemic treatment of 3LL tumor-bearing mice with BLP, but not LPS, led to a dose-dependent tumor regression and a long-lasting protective response against tumor rechallenge. The BLP-mediated tumor remission was neither mediated by a direct tumoricidal activity nor by innate immune cells, because it lacked therapeutic effect in immunodeficient SCID mice. Instead, BLP treatment reduced the suppressive function of Foxp3+ regulatory T cells (Tregs) and enhanced the cytotoxicity of tumor-specific CTL in vitro and in vivo. Furthermore, adoptive cotransfer of BLP-pretreated but not untreated CTL and Tregs from wild-type but not from TLR2−/− mice was sufficient to restore antitumor immunity in SCID mice by reciprocally modulating Treg and CTL function. These results demonstrate that the TLR1/TLR2 agonist BLP may have a general tumor therapeutic property involving reciprocal downregulation of Treg and upregulation of CTL function. This property may play an important role in the development of novel antitumor strategies.

Decrease in Proportion of CD19+CD24hiCD27+ B Cells and Impairment of Their Suppressive Function in Graves’ Disease

IL-10-producing B cells (B10 cells) have been shown to play a suppressive role in the peripheral blood of humans, with their numbers and function altered in several autoimmune diseases. However, the role of B10 cells in Graves’ disease (GD) remains unknown. In this study, we demonstrated that B10 cells in human peripheral blood belonged to a CD24hiCD27+ B cell subpopulation. The proportion of B10 cells along with the CD19+CD24hiCD27+ B cell subset was significantly lower in new-onset patients compared with healthy individuals. In recovered patients, these proportions were restored to levels similar to those seen in healthy individuals. Additionally, we found that CD19+CD24hiCD27+ B cells from healthy individuals inhibited proliferation and TNF-α production of CD4+ T cells via an IL-10–independent pathway. They also inhibited IFN-γ production by CD4+ T cells, through an IL-10–dependent pathway. In contrast, their suppressive function on CD4+ T cell proliferation and cytokine production was impaired in new-onset and recovered patients compared with healthy individuals. Our study provides evidence that CD19+CD24hiCD27+ B cells may possess the capacity to downregulate immune responses, partially by production of IL-10 in human peripheral blood. Impairment of their immunosuppressive function may contribute to GD pathogenesis and relapse.

Critical role of interleukin-17/interleukin-17 receptor axis in mediating Con A-induced hepatitis

Concanavalin A (Con A)‐induced hepatitis is thought to be a T‐cell‐mediated disease with active destruction of liver cells. Interleukin (IL)‐17 is a cytokine produced principally by CD4+ T cells. However, whether IL‐17/IL‐17 receptor (IL‐17/IL‐17R)‐mediated responses are involved in T‐cell‐mediated Con A‐induced liver injury remains unclear. In this study, we found that IL‐17 expression was highly elevated in liver tissues during Con A‐induced hepatitis. The increased levels of IL‐17 were paralleled with the severity of liver injury reflected by Alanine aminotransaminase and histological assay as well as the secretion of tumor necrosis factor (TNF)‐α and IL‐6. Blockage of IL‐17 significantly ameliorated Con A‐induced hepatitis, while overexpression of IL‐17 systemically resulted in massive hepatocyte necrosis in mice. Furthermore, overexpression of an IL‐17R immunoglobulin G1 fusion protein significantly attenuated liver inflammation after acute Con A treatment. High expression of IL‐17R on Kupffer cells was also observed along with the production of cytokines including TNF‐α and IL‐6. Inhibition of Kupffer cells by gadolinium chloride completely prevented Con A‐induced liver injury and cytokine release. Finally, IL‐17‐expressing CD4+ T and natural killer T cells were greatly increased in Con A‐injected mice compared with that in controls. Overall, our results indicate that IL‐17R signaling is critically involved in the pathogenesis in Con A‐induced hepatitis, and blockade of IL‐17/IL‐17R signaling pathway may represent a novel therapeutic intervention in human autoimmune‐related hepatitis.

T regulatory cells and B cells cooperate to form a regulatory loop that maintains gut homeostasis and suppresses dextran sulfate sodium-induced colitis.

Regulatory T cells (Tregs) and B cells present in gut-associated lymphoid tissues (GALT) are both implicated in the resolution of colitis. However, how the functions of these cells are coordinated remains elusive. We used the dextran sulfate sodium (DSS)-induced colitis model combined with gene-modified mice to monitor the progression of colitis, and simultaneously examine the number of Tregs and B cells, and the production of IgA antibodies. We found that DSS-treated mice exhibited more severe colitis in the absence of B cells, and that the adoptive transfer of B cells attenuated the disease. Moreover, the transfer of IL-10−/− B cells also attenuated colitis, suggesting that B cells inhibited colitis through an interleukin-10 (IL-10)-independent pathway. Furthermore, antibody depletion of Tregs resulted in exacerbated colitis. Intriguingly, the number of GALT Tregs in B cell-deficient mice was significantly decreased during colitis and the adoptive transfer of B cells into these mice restored the Treg numbers, indicating that B cells contribute to Treg homeostasis. We also found that B cells induced the proliferation of Tregs that in turn promoted B-cell differentiation into IgA-producing plasma cells. These results demonstrate that B cells and Tregs interact and cooperate to prevent excessive immune responses that can lead to colitis.

BLT1-dependent Alveolar Recruitment of CD4+CD25+ Foxp3+ Regulatory T Cells Is Important for Resolution of Acute Lung Injury

RATIONALE Recent study has demonstrated that CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) present in bronchoalveolar lavage fluid (BALF) contribute to the resolution of an experimental acute lung injury (ALI). However, the molecular mechanism underlying the alveolar recruitment of Treg remains unclear. OBJECTIVES To determine the role of BLT1, a chemotactic receptor for leukotriene B4 (LTB4), in Treg recruitment to BALF of LPS-induced ALI. METHODS We examined BLT1 expression in mouse and human Tregs and evaluated its role in mediating Treg migration in vitro and in vivo. MEASUREMENTS AND MAIN RESULTS We found that BLT1 expression was strongly up-regulated in Tregs on activation, and that BLT1 mediated the migration of activated, but not resting, Tregs toward LTB4 in vitro. LTB4 levels were persistently elevated in BALF of LPS-induced ALI. Blockade of LTB4-BLT1 pathway by administrating antagonists 1 day after LPS exposure significantly decreased BALF Treg numbers and impaired resolution of ALI characterized by persistent BALF protein, neutrophilic infiltrates, and elevated proinflammatory cytokines. Furthermore, there were significantly less BLT1(-/-) Tregs than wild-type Tregs migrating to BALF of LPS-exposed recipient Rag-1(-/-) mice after adoptive transfer (point estimate 299.73; 95% confidence interval, 255.77-343.69; P < 0.00001), and the impaired alveolar recruitment of BLT1(-/-) Tregs caused the inability to restore the resolution of ALI. CONCLUSIONS Our findings reveal a novel antiinflammatory role of BLT1 in the resolution of ALI by mediating the alveolar recruitment of Tregs, and indicate that therapies aimed at interrupting the LTB4-BLT1 pathway after ALI onset could be harmful to the resolution of ALI.

B cells expressing CD11b effectively inhibit CD4+ T-cell responses and ameliorate experimental autoimmune hepatitis in mice.

Increasing evidence in recent years has suggested that B cells act as a crucial regulator in autoimmune diseases. However, little is known about their role in autoimmune hepatitis (AIH) and the underlying regulatory mechanisms. In this study, we show that B cells ameliorated experimental AIH (EAH) by suppressing CD4+ T‐cell responses and that CD11b expression on B cells was required for the regulatory function of B cells. In vitro studies reveal that the suppressive function of CD11b was mediated by the impairment of T‐cell antigen receptor (TCR) signaling transduction and the promotion of TCR down‐regulation. Moreover, we show that the increased CD11b expression on B cells was interleukin (IL)−10 dependent and that additional IL‐10 stimulation promoted CD11b expression on B cells, thereby enhancing B‐cell regulatory effects. Conclusion: These findings reveal a previously unrecognized role for CD11b in B‐cell regulatory function and its protective effect on EAH. (Hepatology 2015;62:1563–1575)

Biological Response Modifier in Cancer Immunotherapy

Biological response modifiers (BRMs) emerge as a lay of new compounds or approaches used in improving cancer immunotherapy. Evidences highlight that cytokines, Toll-like receptor (TLR) signaling, and noncoding RNAs are of crucial roles in modulating antitumor immune response and cancer-related chronic inflammation, and BRMs based on them have been explored. In particular, besides some cytokines like IFN-α and IL-2, several Toll-like receptor (TLR) agonists like BCG, MPL, and imiquimod are also licensed to be used in patients with several malignancies nowadays, and the first artificial small noncoding RNA (microRNA) mimic, MXR34, has entered phase I clinical study against liver cancer, implying their potential application in cancer therapy. According to amounts of original data, this chapter will review the regulatory roles of TLR signaling, some noncoding RNAs, and several key cytokines in cancer and cancer-related immune response, as well as the clinical cases in cancer therapy based on them.

Lipopolysaccharide regulates biosynthesis of cystathionine γ-lyase and hydrogen sulfide through toll-like receptor-4/p38 and toll-like receptor-4/NF-κB pathways in macrophages

Hydrogen sulfide (H2S), formed mainly by the enzyme cystathionine γ-lyase (CSE) in macrophages, is emerging as a novel regulator in inflammation. Although elevated production of H2S has been shown in inflammatory processes, the underlying molecular mechanism remains to be further elucidated. In this study, we compared parallel TLR4 knockout (TLR4−/−) mice with their wild-type counterparts following lipopolysaccharide (LPS) treatment. It showed that LPS increased the expressions of CSE and biosynthesis of H2S in C57BL/6 mice both in vivo and in vitro. However, the effects of LPS were not present in TLR4−/− mice, indicating the crucial role of TLR4 in LPS-induced expression of CSE and biosynthesis of H2S. We subsequently used JNK inhibitor, P38 inhibitor, and ERK inhibitor to block the downstream MAPK pathways of TLR4 in macrophages, and found that LPS-induced CSE expression and H2S synthesizing activity were inhibited by pretreatment with the p38 inhibitor. Similarly, the NF-κB inhibitor (BAY 11-7082) reversed the effects of LPS. These results suggest that LPS increases the biosynthesis of CSE and H2S in macrophages mainly in a TLR4-p38-dependent and TLR-4-NF-κB-dependent manner. These findings expand our knowledge of H2S biosynthesis during inflammation and provide a foundation for the development of novel H2S-based therapies.

Pseudomonas aeruginosa Mannose-Sensitive Hemagglutinin Promotes T-Cell Response via Toll-Like Receptor 4–Mediated Dendritic Cells to Slow Tumor Progression in Mice

Pseudomonas aeruginosa–mannose-sensitive hemagglutinin (PA-MSHA) as a drug may kill tumor cells and has been used clinically. However, the antitumor immune response of PA-MSHA is not completely understood. In this study, we found that treating Lewis lung carcinoma (3LL)-bearing mice with PA-MSHA plus 3LL antigen led to slower tumor progression and longer survival. After PA-MSHA treatment, T-cell number and dendritic cell maturation were both increased significantly at the tumor site. In addition, PA-MSHA in vitro stimulation resulted in the maturation of bone marrow–derived dendritic cells (BMDCs) from naive mice, showing higher costimulatory molecule expression, more cytokine secretion, lower endocytic activity, and stronger capacity to enhance T-cell activation. Toll-like receptor (TLR)4 but not TLR2 was required in the maturation process. More importantly, PA-MSHA–induced DCs were essential for PA-MSHA to enhance activation, expansion, and interferon (IFN)-γ secretion of TLR4-mediated T cells, which play a role in the antitumor effect of PA-MSHA. Thus, this study reveals PA-MSHA as a novel TLR4 agonist that elicits antitumor immune response to slow tumor progression.

Self DNA from Lymphocytes That Have Undergone Activation-Induced Cell Death Enhances Murine B Cell Proliferation and Antibody Production

Systemic lupus erythematosus (SLE) is characterized by prominent autoinflammatory tissue damage associated with impaired removal of dying cells and DNA. Self DNA-containing immune complexes are able to activate both innate and adaptive immune responses and play an important role in the maintenance and exacerbation of autoimmunity in SLE. In this study, we used DNA from lymphocytes that have undergone activation-induced cell death (ALD-DNA) and analyzed its role on the activation and differentiation of B cells from normal BALB/c mice as well as lupus-prone MRL+/+ and MRL/lpr mice. We found that ALD-DNA directly increased the expression of costimulatory molecules and the survival of naïve B cells in vitro. Although ALD-DNA alone had little effect on the proliferation of naïve B cells, it enhanced LPS-activated B cell proliferation in vitro and in vivo. In addition, ALD-DNA increased plasma cell numbers and IgG production in LPS-stimulated cultures of naïve B cells, in part via enhancing IL-6 production. Importantly, B cells from lupus mice were hyperresponsive to ALD-DNA and/or LPS relative to normal control B cells in terminal plasma cell differentiation, as evidenced by increases in CD138+ cell numbers, IgM production, and mRNA levels of B lymphocyte-induced maturation protein-1 (Blimp-1) and the X-box binding protein 1 (XBP1). Furthermore, ALD-DNA enhanced CD40-activated naïve B cell proliferation. Collectively, these data indicate that self DNA can serve as a DAMP (damage-associated molecular pattern) that cooperates with signals from both innate and adaptive immunity to promote polyclonal B cell activation, a common characteristic of autoimmune diseases.