Elevation in the counts of IL-35-producing B cells infiltrating into lung tissue in mycobacterial infection is associated with the downregulation of Th1/Th17 and upregulation of Foxp3+Treg.

IL-35 is an anti-inflammatory cytokine and is thought to be produced by regulatory T (Treg) cells. A previous study found that IL-35 was upregulated in the serum of patients with active tuberculosis (ATB), and IL-35-producing B cells infiltrated to tuberculous granuloma of patients with ATB. Purified B cells from such patients generated more IL-35 after stimulation by antigens of Mycobacterium tuberculosis and secreted more IL-10. However, the function and the underlying mechanisms of IL-35-producing B cells in TB progression have not been investigated. The present study found that the expression of mRNA of IL-35 subsets Ebi3 and p35 was elevated in mononuclear cells from peripheral blood, spleen, bone marrow, and lung tissue in a mouse model infected with Mycobacterium bovis BCG, as tested by real-time polymerase chain reaction. Accordingly, the flow cytometry analysis showed that the counts of a subset of IL-35+ B cells were elevated in the circulating blood and in the spleen, bone marrow, and lung tissue in BCG-infected mice, whereas anti-TB therapy reduced IL-35-producing B cells. Interestingly, BCG infection could drive the infiltration of IL-35-producing B cells into the lung tissue, and the elevated counts of IL-35-producing B cells positively correlated with the bacterial load in the lungs. Importantly, the injection of exogenous IL-35 stimulated the elevation in the counts of IL-35-producing B cells and was associated with the downregulation of Th1/Th17 and upregulation of Foxp3+Treg.The study showed that a subset of IL-35-producing B cells might take part in the downregulation of immune response in mycobacterial infection.

Interleukin-22 receptor 1 is expressed in multinucleated giant cells: A study on intestinal tuberculosis and Crohn's disease.

BACKGROUND: It is challenging to distinguish intestinal tuberculosis from Crohn's disease due to dynamic changes in epidemiology and similar clinical characteristics. Recent studies have shown that polymorphisms in genes involved in the interleukin (IL)-23/IL-17 axis may affect intestinal mucosal immunity by affecting the differentiation of Th17 cells. AIM: To investigate the specific single-nucleotide polymorphisms (SNPs) in genes involved in the IL-23/IL-17 axis and possible pathways that affect susceptibility to intestinal tuberculosis and Crohn's disease. METHODS: We analysed 133 patients with intestinal tuberculosis, 128 with Crohn's disease, and 500 normal controls. DNA was extracted from paraffin-embedded specimens or whole blood. Four SNPs in the IL23/Th17 axis (IL22 rs2227473, IL1ß rs1143627, TGFß rs4803455, and IL17 rs8193036) were genotyped with TaqMan assays. The transcriptional activity levels of different genotypes of rs2227473 were detected by dual luciferase reporter gene assay. The expression of IL-22R1 in different intestinal diseases was detected by immunohistochemistry. RESULTS: The A allele frequency of rs2227473 (P = 0.030, odds ratio = 0.60, 95% confidence interval: 0.37-0.95) showed an abnormal distribution between intestinal tuberculosis and healthy controls. The presence of the A allele was associated with a higher IL-22 transcriptional activity (P < 0.05). In addition, IL-22R1 was expressed in intestinal lymphoid tissues, especially under conditions of intestinal tuberculosis, and highly expressed in macrophage-derived Langhans giant cells. The results of immunohistochemistry showed that the expression of IL-22R1 in patients with Crohn's disease and intestinal tuberculosis was significantly higher than that in patients with intestinal polyps and colon cancer (P < 0.01). CONCLUSION: High IL-22 expression seems to be a protective factor for intestinal tuberculosis. IL-22R1 is expressed in Langhans giant cells, suggesting that the IL-22/IL-22R1 system links adaptive and innate immunity.

MTB driven B cells producing IL-35 and secreting high level of IL-10 in the patients with active pulmonary tuberculosis.

Regulatory B cells (Bregs) have critical roles as a negative regulator of immunity, mainly due to the fact that it secrets high a level of interleukin 10 (IL-10). Recently, a new subset of Bregs was identified as a key source of IL-35, which is an immunosuppressive cytokine and conventionally thought to be secreted by regulatory T cells (Tregs). Our previous study showed that the level of IL-35 in serum was elevated in the patients with active tuberculosis (ATB). However, none of the studies reported that IL-35 is secreted by B cells in ATB patients. In the current study, we found that the mRNA expressions of the both subunits (p35 and Ebi3) of IL-35 by circulating B cells were increased in ATB patients. By using immunohistochemistry and immunofluorescence staining, we found a subset of B cells infiltrated into the tuberculous granuloma of ATB patients also expressed IL-35. Moreover, Mycobacterium tuberculosis (MTB) lysate stimulation assay also demonstrated higher levels of IL-35 were exerted by MTB lysate within purified B cells from healthy control group (HC). Flow cytometry analysis further showed that the IL-35-producing B cells from ATB patients produced a higher level of IL-10. Taken together, IL-35-producing B cells may play a regulatory role during MTB infection by producing IL-10.

Profiling dendritic cell subsets in the patients with active pulmonary tuberculosis.

Dendritic cell (DC) plays an important role in the immune response against pulmonary tuberculosis. However, the phenotypic profile of DC subsets in peripheral blood in individuals with active pulmonary tuberculosis (APT) is still inconclusive. Here, we demonstrated that the absolute numbers of total DC (tDC), myeloid DC (mDC) and plasmacytoid DC (pDC) in individuals with APT were decreased compared to healthy controls (HCs). The decreased number of DCs, especially of pDC, seems to be a useful diagnostic marker of APT. Meanwhile, the number of DCs was associated with the prolonged/complicated TB, ATD treatment effect and lymphocyte immune reactions, as manifested that relapsed APT patients with a higher number of tDC and lower number of pDC compared to newly diagnosed patients. Interestingly, mDC from APT patients displayed high expressions of CD83 and CCR7, but pDC displayed low expressions of CD83 and CCR7. Moreover, DCs from APT patients expressed lower levels of HLA-DR and CD80, but expressed a higher level of CD86 than those from HCs. However, the antigen uptake capacity of DC subsets was not different between APT and HCs, despite the antigen uptake capacity of pDC was much lower than that of mDC in both APT patients and HCs. Our data represent a systematic profile of DC subsets in the blood of APT patients, and would represent a useful biomarker for APT.

Regulatory B cells in infectious disease (Review).

Regulatory B cells (Bregs) are a subset of B cells, which reportedly exert significant immunomodulatory effects through the production of interleukin (IL)­10, IL­35 and transforming growth factor­ß. Over the last decade, studies have indicated that Bregs function in autoimmune and allergic diseases through antigen­specific and non­specific immunoregulatory mechanisms. However, only a limited number of reviews have focused on the role of Bregs during infection, particularly their functions in intracellular infections. The present review discusses the role of Bregs in infectious diseases in animal models and human studies, and provides an overview of the immunoregulatory mechanisms used by Bregs.

Development and characterization of monoclonal antibody against human IL-37b.

IL-37 has been described as a natural inhibitor of immune responses. Monoclonal antibody (mAb) against human IL-37b with high affinity and specificity can serve as a molecular probe to detect IL-37 and study IL-37 functions, mechanisms and related signal pathways in inflammatory diseases. However, there are very few such mAbs against human IL-37 commercially available so far. In the current study, monoclonal antibodies against human IL-37b were developed by fusing splenocytes from immunized mouse with SP2/0 myeloma cells and polyethylene glycol. Then the antibodies were screened with prokaryotic expressed human IL-37b protein and eukaryotic expressed human IL-37b protein subsequently. Western blot and flow cytometry analysis revealed that selected mAb clons were able to recognize human IL-37 with high specificity. And more importantly, the IL-37b mAbs were fluorescently labeled and can be directly used in flow cytometry and immunohistochemistry. In conclusion, the current study developed new mAbs against human IL-37b, which are applicable in flow cytometry and immunohistochemistry.

BTLA-expressing CD11c antigen presenting cells in patients with active tuberculosis exhibit low capacity to stimulate T cell proliferation.

Despite past extensive studies on B and T lymphocyte attenuator (BTLA)-mediated negative regulation of T cell activation, the role of BTLA in antigen presenting cells (APCs) in patients with active pulmonary tuberculosis (ATB) remains poorly understood. Here, we demonstrate that BTLA expression on CD11c APCs increased in patients with ATB. Particularly, BTLA expression in CD11c APCs was likely associated with the attenuated stimulatory capacity on T cells (especially CD8+ T cell) proliferation. BTLA-expressing CD11c APCs showed lower antigen uptake capacity, lower CD86 expression, higher HLA-DR expression, and enhanced IL-6 secretion, compared to counterpart BTLA negative CD11c APCs in healthy controls (HC). Interestingly, BTLA-expressing CD11c APCs from ATB patients displayed lower expression of HLA-DR and less IL-6 secretion, but higher expression of CD86 than those from HC volunteers. Mixed lymphocyte reaction suggests that BTLA expression is likely associated with positive rather than conventional negative regulation of CD11c APCs stimulatory capacity. This role is impaired in ATB patients manifested by low expression of HLA-DR and low production of IL-6. This previous unappreciated role for BTLA may have implications in the prevention and treatment of patients with ATB.

Tuberculosis-sensitized monocytes sustain immune response of interleukin-37.

Roles of human IL-37 in infections remain poorly characterized. Although plasma IL-37 is elevated in patients with tuberculosis (TB), IL-37 source and immune correlate in TB have not been investigated. It is also unknown whether and how TB can influence the ability of immune cells to mount innate responses of IL-37 and pre-inflammatory cytokines. Here, we demonstrated that IL-37b-producing monocytes coincided with a source of elevated plasma IL-37b in TB patients. While IL-37b production in TB was associated with prolonged/complicated TB, TB burdens and inflammatory reactions, it negatively correlated with immune responses of pro-inflammatory cytokines IL-1ß, IL-6 and TNF-α or IL-10. Interestingly, mycobacterial re-infection of monocytes from TB patients, but not healthy BCG-vaccinated controls, enhanced or sustained IL-37b production by cultured monocytes. TB-sensitized monocytes from TB patients mounted more robust immune responses of IL-37b than those of pre-inflammatory cytokines during mycobacterial re-infection in culture. Our data represent new findings in terms of IL-37b responses, immune correlates and potential mechanisms in TB patients.

IL-6 Inhibition Reduces STAT3 Activation and Enhances the Antitumor Effect of Carboplatin.

Recent studies suggest that tumor-associated macrophage-produced IL-6 is an important mediator within the tumor microenvironment that promotes tumor growth. The activation of IL-6/STAT3 axis has been associated with chemoresistance and poor prognosis of a variety of cancers including colorectal carcinoma and thus serves as a potential immunotherapeutic target for cancer treatment. However, it is not fully understood whether anticytokine therapy could reverse chemosensitivity and enhance the suppressive effect of chemotherapy on tumor growth. In this study, we aimed to investigate the effect of IL-6 inhibition therapy on the antitumor effect of carboplatin. Enhanced expression of IL-6 and activation of STAT3 were observed in human colorectal carcinoma samples compared to normal colorectal tissue, with higher levels of IL-6/STAT3 in low grade carcinomas. Treatment of carboplatin (CBP) dose-dependently increased IL-6 production and STAT3 activation in human colorectal LoVo cells. Blockade of IL-6 with neutralizing antibody enhanced chemosensitivity of LoVo cells to carboplatin as evidenced by increased cell apoptosis. IL-6 blockade abolished carboplatin-induced STAT3 activation. IL-6 blockade and carboplatin synergistically reduced cyclin D1 expression and enhanced caspase-3 activity in LoVo cells. Our results suggest that inhibition of IL-6 may enhance chemosensitivity of colon cancers with overactive STAT3 to platinum agents.

Antitumor effect and mechanism of action of a tumor-targeting recombinant human tumor necrosis factor-α fusion protein mediated by urokinase.

The aim of this study was to investigate the effect of the tumor­targeting recombinant human tumor necrosis factor (rhTNF)­α fusion protein mediated by urokinase on Sl80 tumor­bearing mice, as well as to explore its mechanisms of action. Furthermore, the study aimed to observe the effect of the protein on liver and kidney function. rhTNF­α fusion protein prokaryotic expression vectors were constructed using genetic engineering techniques, and were introduced into Escherichia coli. Expression of the fusion protein was induced, and it was then separated and purified in order to determine its cytotoxic activity on L929 cells. Kunming mice were randomly divided into four groups after being inoculated with S180 tumor cells. The groups were then injected with saline (control group, group S), or saline with 0.1 µg/ml fusion protein (low dose group, group L), 0.2 µg/ml fusion protein (middle dose group, group M) or 0.3 µg/ml (high dose group, group H). The mice were sacrificed after 12 days and liver [mg/kg; (liver weight/body weight) x 1,000] and kidney [mg/kg; (kidney weight/body weight) x 1,000] indices, tumor weight, the percentage reduction in mean tumor size, and the levels of alanine transaminase (ALT), albumin (ALB), creatinine (Cr) and blood urea nitrogen (BUN) in each group of mice were determined. In addition, the levels of urokinase­type plasminogen activator (uPA), the expression of bcl­2, bax and vascular endothelial growth factor (VEGF), and the percentage of apoptotic cells were measured with an enzyme­linked immunosorbent assay, streptavidin­biotin complex of immunohistochemistry and terminal deoxynucleotidyl transferase­mediated dUTP nick end labeling, respectively. The fusion protein significantly inhibited the growth of S180 tumor cells in vivo in a dose­dependent manner. With an increase in the dose of fusion protein, ALT, uPA, bcl­2 and VEGF levels decreased, and ALB levels increased. However, liver and kidney indices and bax expression were not significantly altered. Cr and BUN levels did not change significantly in the low and middle dose groups, but did increase in the high dose group. Compared with the control group, the percentage of apoptotic cells in the high­dose group was significantly higher. In conclusion, the fusion protein significantly inhibited S180 tumor growth in a mouse model, possibly by reducing the levels of uPA, bcl­2 and VEGF. There was a mildly toxic effect on the kidneys with the high dose, but a protective effect in the liver.