Murine Flt3 ligand-generated plasmacytoid and conventional dendritic cells display functional differentiation in activation, inflammation, and antigen presentation during BCG infection in vitro

Discrepancy in Response of Mouse Dendritic Cells against BCG: Weak Immune Effects of Plasmacytoid Dendritic Cells Compared to Classical Dendritic Cells despite the Uptake of Bacilli

Tuberculosis (TB), a zoonosis characterized by chronic respiratory infections, is mainly caused by Mycobacterium tuberculosis and is associated with one of the heaviest disease burdens in the world. Dendritic cells (DCs) play a key role and act as a bridge between innate and adaptive immune responses against TB. DCs are divided into distinct subsets. Currently, the response of DCs to mycobacterial infections is poorly understood. Herein, we aimed to evaluate the responses of splenic conventional DCs (cDC) and plasmacytoid DCs (pDC), subsets to Bacillus Calmette–Guérin (BCG) infection in mice. Splenic pDC had a significantly higher infection rate and intracellular bacterial count than cDC and the CD8+ and CD8− cDC subsets after BCG infection. However, the expression levels of CD40, CD80, CD86, and MHC-II molecules were significantly upregulated in splenic cDC and the CD8 cDC subsets compared to pDC during BCG infection. Splenic cDC had a higher expression of IFN-γ and IL-12p70 than pDC, whereas pDC had higher levels of TNF-α and MCP-1 than cDC in mice infected with BCG. At early stages of immunization with BCG containing the Ag85A protein, splenic cDC and pDC could present the Ag85A peptide to a specific T hybridoma; however, cDC had a stronger antigen presenting activity than pDC. In summary, splenic cDC and pDC extensively participate in mouse immune responses against BCG infection in vivo. Although pDC had a higher BCG uptake, cDC induced stronger immunological effects, including activation and maturation, cytokine production, and antigen presentation.

MicroRNA-5112 Targets IKKγ to Dampen the Inflammatory Response and Improve Clinical Symptoms in Both Bacterial Infection and DSS-Induced Colitis

Inflammation is a double-edged sword that can be induced by various PAMPs, resulting in the control of infection by invading pathogens or injuries. The inflammatory response requires strict and precise control and regulation. MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression via translational inhibition or mRNA degradation. However, the role of miRNAs in inflammation induced by flagellin (ligand of TLR5) has yet to be fully determined. In this study, we identified differentially expressed miRNAs in murine bone marrow-derived dendritic cells (BMDCs) between flagellin treatment and medium alone using miRNA microarray. We found that flagellin stimulation downregulated miR-5112 expression in BMDCs and spleen DCs in vitro and in vivo. The overexpression of miR-5112 decreased inflammatory cytokine production, accompanied by a reduction of IKKγ in flagellin-stimulated BMDCs. We demonstrated that miR-5112 could directly target IKKγ to inhibit inflammatory cytokine production. Furthermore, miR-5112 inhibited the inflammatory response induced by flagellin or Salmonella infection in vivo. Interestingly, miR-5112 could also dampen the inflammatory response and alleviate dextran sulfate sodium (DSS)-induced colitis in C57BL/6 mice. These results suggest that miR-5112 could be a novel therapeutic target for both bacterial infection and DSS-induced colitis model.

The Collective Effect of MIP-3α and FL Promotes Dendritic Cell Function Within the Immune Microenvironment of Murine Liver Cancer

Hepatocellular carcinoma is a highly malignant and lethal tumor. In addition to surgery, immunotherapy is currently a more effective treatment for hepatocellular carcinoma. The tumor immune microenvironment (TIME) largely determines the efficacy of cancer immunotherapy. Based on the universal targeting of TIME modulators in clinical treatment, TIME modulators are promising targets for tumor immunotherapy. We investigated the effect of a double gene expression vector (recombinant galactose-terminal glycol-poly-L-lysine coupled MIP-3α-FL) on dendritic cells (DCs) regulation within the TIME of mice with liver cancer. H22 cells were transfected with a recombinant MIP-3α-FL plasmid to induce DCs differentiation and chemotaxis. The effects of transfection were investigated by flow cytometry following the modified Boyden’s method. Cytokine-induced killer (CIK) cells co-culture revealed changes in the antigen presentation ability of DCs. Further, tumor-bearing mice were injected with the recombinant double gene vector via the tail vein. We compared the survival time, tumor volume, weight of the mice, as well as the number and phenotype of tumor-infiltrating DCs (TIDCs) between groups. The supernatant of transfected H22 cells promoted the phenotypic maturation of DCs, enhancing their chemotaxis. Further, treated DCs promoted the cytokine secretion and killing ability of CIK cells. The survival time of mice injected with the double gene vector was significantly prolonged, while their tumor weight and volume were relatively reduced. Flow cytometry revealed that the number of TIDCs (as well as CD80 and CD86 expression) in the Mouse^MIP-3α-FL group, were significantly higher than in the control group. The combination of MIP-3α and FL can significantly promote DCs aggregation, maturation, and enhance their antigen presentation ability. The coupling of the double gene vector with glycosylated polylysine can improve the precise targeting of the liver and inhibit tumor growth in vivo, providing a novel approach for immune therapy in liver cancer.

I-alowCD11bhigh DC Regulates the Immune Response in the Eyes of Experimental Autoimmune Uveitis

Regulatory dendritic cells (DC_reg) have been reported to be a negative regulator in the immune response. These cells are widely distributed in the liver, spleen, and lung. However, the status and function of DC_reg in the eyes and disease are still not very clear. Herein, we found that the number of I-a^lowCD11b^high DC increased in the eye and spleen at the recovery stage of experimental autoimmune uveitis (EAU), which is a mouse model for autoimmune uveitis. These cells expressed lower levels of CD80, CD86, and CD54 than the mature DCs and expressed interleukin 10 (IL-10), indoleamine 2,3-dioxygenase (IDO), and transforming growth factor beta (TGF-β) as well. Moreover, these DC_reg can regulate the development of EAU by promoting CD4⁺CD25⁺Foxp3⁺ regulatory T cells. The increased interferon-gamma (IFN-γ) in the aqueous humor of EAU participates in inducing DC_reg to alleviate the symptom of EAU. Furthermore, DC_reg was found to exist in the eyes of normal mice. Aqueous humor, containing a certain concentration of IL-10, TGF-β, prostaglandin E2 (PGE2), IDO, and nitric oxide (NO), induced the tolerance of DC_reg in normal eyes. It can be concluded that DC_reg exists in the eyes and plays a protective role in inflamed eyes. These DC_reg induced by IFN-γ might be used as a strategy to develop therapy for EAU management.