Mycobacterial inositol phosphoglycans and their effects on macrophages

Ligand binding of a number of growth factors and cytokines can result in the release of mediators known as inositol phosphoglycans (IPG) catalyzed by a glycosyl phosphatidylinositol specific phospholipase D. Two distinct subtractions of IPG derived from M. vaccae were able to mimic metabolic effects of mammalian IPG such as activating pyruvate dehydrogenase phosphatase and stimulating lipogenesis in adipocytes. In contrast, the IPG isolated from M. tuberculosis H37Rv were inhibitory in the mammalian assay systems, leading to the speculation that they might exert pathogenic roles in infected cells. Therefore, the effects of the IPG from M. vaccae and M. tuberculosis were evaluated on the functions of a murine macrophage cell line, J774A.1. Mycobacterial IPG of both fractions were not able to stimulate nitrite production in J774A.1 cells. However, they can synergise with IFN-[gamma] to produce high levels of nitrite. Western blotting analysis of the J774A.1 cell lysates treated with mycobacterial IPG plus IFN-[gamma] showed that the nitrite produced was attributed to the induction of inducible nitric oxide synthase protein. Unlike lipopolysaccharides (LPS), mycobacterial IPG-induced nitrite production was not inhibited by polymyxin B. However, LPS and mycobacterial IPG-induced nitrite production were inhibited by the L-arginine analogue, NG-monomethyl-L-arginine (L-NMMA) but not by its inert enantiomer, NG-monomethyl-D-arginine (D-NMMA). As IPG are released by GPI-PLD, an enzyme assay system using [3H] myristate-labelled membrane-form variant surface glycoprotein (mfVSG) was set up to monitor the purification of GPI-PLD. It was found mannosylated lipoarabinomannan (ManLAM) inhibits GPI-PLD, raising the possibility that in mammalian cells the mycobacterial LAM inhibits release of endogenous IPG, while the mycobacterium substitutes its own IPG, resulting in subtly disordered regulation of macrophage function

Establishing criteria for human mesenchymal stem cell potency

This study sought to identify critical determinants of mesenchymal stem cell (MSC) potency using in vitro and in vivo attributes of cells isolated from the bone marrow of age‐ and sex‐matched donors. Adherence to plastic was not indicative of potency, yet capacity for long‐term expansion in vitro varied considerably between donors, allowing the grouping of MSCs from the donors into either those with high‐growth capacity or low‐growth capacity. Using this grouping strategy, high‐growth capacity MSCs were smaller in size, had greater colony‐forming efficiency, and had longer telomeres. Cell‐surface biomarker analysis revealed that the International Society for Cellular Therapy (ISCT) criteria did not distinguish between high‐growth capacity and low‐growth capacity MSCs, whereas STRO‐1 and platelet‐derived growth factor receptor alpha were preferentially expressed on high‐growth capacity MSCs. These cells also had the highest mean expression of the mRNA transcripts TWIST‐1 and DERMO‐1. Irrespective of these differences, both groups of donor MSCs produced similar levels of key growth factors and cytokines involved in tissue regeneration and were capable of multilineage differentiation. However, high‐growth capacity MSCs produced approximately double the volume of mineralized tissue compared to low‐growth capacity MSCs when assessed for ectopic bone‐forming ability. The additional phenotypic criteria presented in this study when combined with the existing ISCT minimum criteria and working proposal will permit an improved assessment of MSC potency and provide a basis for establishing the quality of MSCs prior to their therapeutic application

A Co-culture Model of PBMC and Stem Cell Derived Human Nasal Epithelium Reveals Rapid Activation of NK and Innate T Cells Upon Influenza A Virus Infection of the Nasal Epithelium

Background: We established an in vitro co-culture model involving H3N2-infection of human nasal epithelium with peripheral blood mononuclear cells (PBMC) to investigate their cross-talk during early H3N2 infection. Methods: Nasal epithelium was differentiated from human nasal epithelial stem/progenitor cells and cultured wtih fresh human PBMC. PBMC and supernatants were harvested after 24 and 48 h of co-culture with H3N2-infected nasal epithelium. We used flow cytometry and Luminex to characterize PBMC subpopulations, their activation and secretion of cytokine and chemokines. Results: H3N2 infection of the nasal epithelium associated with significant increase in interferons (IFN-alpha, IFN-gamma, IL-29), pro-inflammatory cytokines (TNF-alpha, BDNF, IL-3) and viral-associated chemokines (IP-10, MCP-3, I-TAC, MIG), detectable already after 24 h. This translates into rapid activation of monocytes, NK-cells and innate T-cells (MAIT and gamma delta T cells), evident with CD38+ and/or CD69+ upregulation. Conclusions: This system may contribute to in vitro mechanistic immunological studies bridging systemic models and possibly enable the development of targeted immunomodulatory therapies.Peer reviewe

FUT6 deficiency compromises basophil function by selectively abrogating their sialyl-Lewis x expression.

Sialyl-Lewis x (sLex, CD15s) is a tetra-saccharide on the surface of leukocytes required for E-selectin-mediated rolling, a prerequisite for leukocytes to migrate out of the blood vessels. Here we show using flow cytometry that sLex expression on basophils and mast cell progenitors depends on fucosyltransferase 6 (FUT6). Using genetic association data analysis and qPCR, the cell type-specific defect was associated with single nucleotide polymorphisms (SNPs) in the FUT6 gene region (tagged by rs17855739 and rs778798), affecting coding sequence and/or expression level of the mRNA. Heterozygous individuals with one functional FUT6 gene harbor a mixed population of sLex+ and sLex- basophils, a phenomenon caused by random monoallelic expression (RME). Microfluidic assay demonstrated FUT6-deficient basophils rolling on E-selectin is severely impaired. FUT6 null alleles carriers exhibit elevated blood basophil counts and a reduced itch sensitivity against insect bites. FUT6-deficiency thus dampens the basophil-mediated allergic response in the periphery, evident also in lower IgE titers and reduced eosinophil counts

Whole blood immunophenotyping uncovers immature neutrophil-to-VD2 T-cell ratio as an early marker for severe COVID-19

COVID-19 severity is associated with cytokine levels and lymphopenia, but the role of immune cell subsets is not well understood. Here the authors immunophenotype whole blood samples from 54 COVID-19 patients and find that the immature neutrophil-to-VD2 T-cell ratio is associated with severe COVID-19

Data-Driven Analysis of COVID-19 Reveals Persistent Immune Abnormalities in Convalescent Severe Individuals

Severe SARS-CoV-2 infection can trigger uncontrolled innate and adaptive immune responses, which are commonly associated with lymphopenia and increased neutrophil counts. However, whether the immune abnormalities observed in mild to severely infected patients persist into convalescence remains unclear. Herein, comparisons were drawn between the immune responses of COVID-19 infected and convalescent adults. Strikingly, survivors of severe COVID-19 had decreased proportions of NKT and Vδ2 T cells, and increased proportions of low-density neutrophils, IgA+/CD86+/CD123+ non-classical monocytes and hyperactivated HLADR+CD38+ CD8+ T cells, and elevated levels of pro-inflammatory cytokines such as hepatocyte growth factor and vascular endothelial growth factor A, long after virus clearance. Our study suggests potential immune correlates of “long COVID-19”, and defines key cells and cytokines that delineate true and quasi-convalescent states

Functional CTLA-4 variants associate to both allergic asthma and rhinitis potentially by modulating naïve regulatory T cells.

10.1111/all.15386Allerg

Resistin expression in human monocytes is controlled by two linked promoter SNPs mediating NFKB p50/p50 binding and C-methylation

International audienceResistin is a key cytokine associated with metabolic and inflammatory diseases. Especially in East Asian populations, the expression levels are strongly influenced by genetic polymorphisms. Mechanisms and functional implications of this genetic control are still unknown. By employing reporter assays, EMSA, inhibition studies, bisulphite sequencing, ChIP-Seq and gene-editing we show that the p50/p50 homodimer known to act as repressor for a number of pro-inflammatory genes plays a central role in the genetic regulation of resistin in monocytes along with promoter methylation. In the common RETN haplotype p50/p50 constitutively dampens the expression by binding to the promoter. In an Asian haplotype variant however this interaction is disrupted by the A allele of rs3219175. The SNP is in very close linkage to rs34861192, a CpG SNP, located 280 bp upstream which provides an allele-specific C-methylation site. rs34861192 is located in a 100 bp region found to be methylated in the common but not in the Asian haplotype, resulting in the latter having a higher basal expression, which also associates with elevated histone acetylation (H3K27ac). Genotype associations within cohort data of 200 East Asian individuals revealed significant associations between this haplotype and the plasma levels of factors such as TGF-b, S100B, sRAGE and IL-8 as well as with myeloid DC counts. Thus, the common RETN haplotype is tightly regulated by the epigenetic mechanism linked to p50/p50-binding. This control is lost in the Asian haplotype, which may have evolved to balance the antagonistic Retn effects on pathogen protection vs. metabolic and inflammatory disease induction