(2006) 26:104–15. After 6 h of co-incubation, the extent of microparticle uptake was assessed within conventional CD11c+ dendritic cells. However, the cell–cell interaction can also take place at a distance via cytokines . In contrast, we found that plasmin elicited no change in the release of IL-6 from dendritic cells (Fig 3A). Vuckovic S, Withers G, Harris M, Khalil D, Gardiner D, Flesch I, et al. Diabetes. Cell Immunol. Thus, four different subsets of DCs in peripheral blood [total DCs, myeloid DCs (myDCs), plasmacytoid DCs (pDCs) and a CD11c−CD123− putative DC subset] were analyzed (Figure 1) following the gating strategy displayed in Figure S1. However, the engulfment of these liposomes by DCs induces similar effects to those observed by physiological apoptotic cell phagocytosis and constitutes a good system to test the fitness of DCs. (2018) 9:253. doi: 10.3389/fimmu.2018.00253, 22. Consistent with the notion that plasmin does not cause dendritic cell maturation, plasmin generation was found to decrease expression of CD86, CD70, CD80, CD274 and HLA-DR in MoDCs (Fig 3C and S1 and S4 Figs. are also recipients of National Health and Medical Research Council Principal Research Fellowship (R.L.M. SR-F, FV, and MV-P designed the experiments. The primary antibodies used were goat anti-t-PA (Santa Cruz Biotechnology, Dallas USA, sc-5239; 1:1000 dilution), sheep anti-plasminogen (Serotec Kidlington, UK, Code: 7440-0104P 1:1000 dilution), mouse anti-GAPDH (Merck Millipore, MAB374; 1:1000 dilution) and mouse anti-Annexin A2 (BD Biosciences; 1:1000 dilution). Department of Medicine, Monash University, Alfred Medical Research and Education Precinct, Melbourne, 3004, Victoria, Australia, Liposomes were prepared using the thin-film hydration method from a lipid mixture of 1,2-dioleoyl-sn-glycero-3-phospho-L-serine, 1,2-didodecanoyl-sn-glycero-3-phosphocholine and cholesterol at 1:1:1.33 molar ratio, respectively, as described (20). Gene expression signals were normalized to GAPDH expression. Acquisition software was MetaMorph v.7.5 (Molecular Devices, Sunnyvale, CA, USA). Treatment of MoDCs with a 10-fold lower concentration of plasmin (10 nM) similarly increased microparticle uptake after 3 h (not shown) and 24 h (Fig 2C) of co-incubation. As a case in point, many studies have linked the deficient removal of apoptotic beta cells performed by phagocytes to the initiation of autoimmunity (1). Thus, analogous to plasmin-mediated cleavage of the carboxy-terminus of NR1 , plasmin-mediated cleavage of Annexin A2 appears to be a non-physiological event that occurs following cell lysis. Cells were resuspended at 1x106 cells/mL in serum-free AIM-V media and plated in 24-well plates (500 μL/well). The microbes are engulfed and placed in a phagosome. The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fimmu.2019.02811/full#supplementary-material. Moreover, addition of the Annexin A2-derived cleavage fragment failed to recapitulate the influence of plasmin on MoDCs  and we were unable to demonstrate increased phospho-ERK1/2 or phospho-Akt following plasmin-treatment of MoDCs (not shown). Camera: Hamamatsu ORCA-AG. Dendritic cells (DCs) are outstanding antigen presenting cells (APCs) due to their robust ability to internalize extracellular antigens using endocytic processes such as receptor-mediated endocytosis, phagocytosis, and macropinocytosis. Previous studies have shown that the uptake of microparticles by dendritic cells is an actin-dependent process, whereas the uptake of nanoparticles (40 nm in diameter) uses cholesterol/caveolae and clathrin-mediated endocytic mechanisms [17,21–23]. They bind to pathogens and internalise them in a phagosome, which acidifies and fuses with lysosomes in order to destroy the contents. Type 1 diabetes (T1D) is prompted by defective immunological tolerance, an event in which dendritic cells (DCs) are crucial as immune response orchestrators. doi: 10.1096/fj.04-1853fje, 41. After 3 h of co-incubation, plasmin significantly increased both the number of microparticles per cell (Fig 2A) and the number of MoDCs with internalized microparticles (Fig 2B). (n = 8–11 independent experiments). The activation of the dendritic cells mainly occurs through the inflammatory cytokines secreted by macrophages. In fact, when the clinical diagnosis of T1D takes place, there is already a significant loss of beta cells in the pancreas of the patient. *p<0.05 by 2-tailed Welch’s unequal variances t-test. The relative number of particle-positive MoDCs was assessed by flow cytometry 24 h later. On these considerations, we hypothesise that the pro-phagocytic effect of plasmin involves altered PDGF receptor signalling, but this requires further investigation. Ellis LM, Hicklin DJ. No, Is the Subject Area "Flow cytometry" applicable to this article? This effect was distinct from the ability of plasmin to proteolytically degrade necrotic material, as plasmin also increased the phagocytosis of protease-resistant microparticles. Plasmin cleaves and thereby reduces the expression of numerous cell-surface immunomodulatory receptors, which in turn may help maintain an immature phenotype. (2017) 8:1356. doi: 10.3389/fimmu.2017.01356, 35. Quite unexpectedly, here we found that the phagocytic activity of monocyte-derived DCs from pediatric patients with T1D was impaired, and this defect deteriorated with the progression of the disease but did not affect the induction of a tolerogenic phenotype after phagocytosis. Pujol-Autonell I, Serracant-Prat A, Cano-Sarabia M, Ampudia RM, Rodriguez-Fernandez S, Sanchez A, et al. Significant differences were found when comparing the same culture conditions in the three groups (+p < 0.05, ++p < 0.01, Mann-Whitney test). Independent of direct NCC-proteolysis, an immature dendritic cell comes into physical contact with the plasmin-bearing necrotic cell. This was concluded from in vitro mixed lymphocyte reactions (Fig 4) and in vivo studies as plasmin-induced microparticle uptake after intradermal injection did not result in dendritic cell maturation or increased migration to the draining lymph nodes (Fig 6). ****p<0.0001 by 1-way ANOVA with Newman-Keuls post-hoc analysis. The ubiquitin-editing protein A20 prevents dendritic cell activation, recognition of apoptotic cells, and systemic autoimmunity. doi: 10.2337/dc11-2460, 30. How apoptotic β-cells direct immune response to tolerance or to autoimmune diabetes: a review. Data are displayed as fold-change in double-positive MoDCs (mean ± s.e.m. Dendritic cells, as well as eliminating dead cells, are also a specialised cell type capable of initiating damaging adaptive immune responses to self-antigens. To assess MoDC maturation status, we measured the extracellular levels of an array of cytokines. Abdolmaleki F, Farahani N, Gheibi Hayat SM, Pirro M, Bianconi V, Barreto GE, et al. Several types of cells of the immune system perform phagocytosis, such as neutrophils, macrophages, dendritic cells, and B lymphocytes. All these genes were expressed in iDCs. The percentage of myDCs was increased in patients at first year when compared to control subjects, patients at onset and at second year of progression, although no differences were observed in their numbers. doi: 10.1111/j.1574-695X.1999.tb01397.x, 18. (2017) 8:909. doi: 10.3389/fimmu.2017.00909, 11. (2017) 376:1419–29. Next, 2x106 Jurkat T lymphocytes were labelled with PKH67 using the same protocol as above. Shown is a representative histogram of n = 1 experiment. Silencing LAIR-1 in human THP-1 macrophage increases foam cell formation by modulating PPARγ and M2 polarization. Mol Metab. These misfolded proteins formed within necrotic cells become exposed as a consequence of plasma membrane disruption and acted as a ligand for tissue-type plasminogen activator (t-PA) and plasminogen [7,8]. 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