These findings imply that PD-1/PD-Ligand pathways are interesting targets to prevent human anti-pig T-cell responses after xenotransplantation, and also suggests that PD-1/PD-Ligand interactions may play a role in the control of the activity and/or homeostasis of regulatory T cells.
The 77C→G mutation in exon A of the human CD45 gene occurs with low frequency in healthy individuals. An enhanced frequency of 77C→G individuals has been reported in cohorts of patients suffering from multiple sclerosis, systemic sclerosis, autoimmune hepatitis, and HIV-1. To investigate the mechanisms by which the variant allele may contribute to disease susceptibility, we compared T cell reactivity in heterozygous carriers of the mutation (healthy individuals and multiple sclerosis patients) and wild-type controls. In vitro-generated T cell lines and freshly isolated CD4+CD45R0+ primed/memory T cells from 77C→G individuals aberrantly expressed CD45RA isoforms and showed enhanced proliferation and IL-2 production when stimulated with anti-TCR/CD3 mAb or Ag. Mutant T cell lines contained a more active pool of p56lck tyrosine kinase and responded with increased phosphorylation of Zap70 and TCR-ζ and an enhanced Ca2+ flux to TCR/CD3 stimulation. These data suggest that 77C→G may act as a risk factor for certain diseases by increasing the intensity of TCR signaling.
Endothelial colony‐forming cells (ECFCs), a proliferative subpopulation of endothelial progenitor cells, are involved in angiogenesis and endothelial repair. In this study, we investigated endothelial barrier characteristics of ECFCs, whether vitamin D supports cell‐cell adhesion and barrier integrity, and how it affects ECFC mobilization and actin dynamics. Although ECFC barrier was disrupted under inflammatory conditions, this effect was rescued by vitamin D treatment, leading to higher stability of an ECFC monolayer. Furthermore, vitamin D enhanced ECFC mobilization toward directional migration. In addition, immunocytochemistry, quantitative real‐time PCR, and immunoblotting analysis showed that vitamin D increased endothelial interconnections through vascular endothelial Cadherin (VE‐cadherin) junctions and by impacting cell dynamics through cofilin and VE‐cadherin phosphorylation. Our results suggest that vitamin D treatment efficiently counteracts inflammation in an ECFC monolayer, resulting in higher ECFC barrier integrity. This study provides evidence of a new beneficial effect of vitamin D for ECFC homeostasis. —Schröder‐Heurich, B., von Hardenberg, S., Brodowski, L., Kipke, B., Meyer, N., Borns, K., von Kaisenberg, C. S., Brinkmann, H., Claus, P., von Versen‐Höynck, F. Vitamin D improves endothelial barrier integrity and counteracts inflammatory effects on endothelial progenitor cells. FASEB J. 33, 9142–9153 (2019). http://www.fasebj.org
Summary Cellular rejection is a relevant hurdle for successful pig‐to‐primate xenotransplantion. We have shown previously that the induction of a human anti‐pig T cell response (in vitro activation of CD4+ T cells) can be suppressed by the overexpression of human negative costimulatory ligands (e.g. programmed death receptor ligand, PD‐L1) on pig antigen presenting cells. Here, we asked whether PD‐L1 mediated enhancement of negative signaling might also be efficient during the effector phase of human anti‐pig cellular immune responses. The porcine B‐cell line L23 was transfected with human PD‐L1, and clones were selected stably expressing PD‐L1 with low, medium, or high density. Mock‐transfected L23 cells were effectively lysed by human cytotoxic effector cells (IL‐2 activated CD8+ T cells and CD56+ cells). The lytic potential of the effectors decreased with increasing levels of PD‐L1 and was reduced by about 50% in L23‐PD‐Lhigh targets. A proportion of activated CD8+ effector cells underwent apoptosis when exposed to PD‐L1 expressing L23 cells. These data suggest that the overexpression of PD‐L1 on target cells may (a) trigger negative signals in effector cells that prevent the release of cytolytic molecules and/or (b) induce apoptosis in the attacking effector cells thereby protecting targets from destruction.
Studying genetic diversity of immunologically relevant molecules can improve our knowledge on their functional spectrum in normal immune responses and may also uncover a possible role of different variants in diseases. We characterized the c.503T>C polymorphism in the human KLRB1 gene (Killer cell lectin-like receptor, subfamily B, member 1) coding for the cell surface receptor CD161. CD161 is expressed by subsets of CD4+ and CD8+ T cells and the great majority of CD56+ natural killer (NK) cells, acting as inhibitory receptor in the latter population. Genotyping a cohort of 118 healthy individuals revealed 40% TT homozygotes, 46% TC heterozygotes, and 14% carriers of CC. There was no difference in the frequency of CD161 expressing CD4+ and CD8+ T cells between the different genotypes. However, the frequency of CD161+ NK cells was significantly decreased in CC carriers as compared to TT homozygotes. c.503T>C causes an amino acid exchange (p.Ile168Thr) in an extracellular loop of the CD161 receptor, which is regarded to be involved in binding of its ligand Lectin-like transcript 1 (LLT1). Binding studies using soluble LLT1-Fc on 293 transfectants over-expressing CD161 receptors from TT or CC carriers suggested diminished binding to the CC variant. Furthermore, triggering of CD161 either by LLT1 or anti-CD161 antibodies inhibited NK cell activation less effectively in cells from CC individuals than cells from TT carriers. These data suggest that the c.503T>C polymorphism is associated with structural alterations of the CD161 receptor. The regulation of NK cell homeostasis and activation apparently differs between carriers of the CC and TT variant of CD161.
Background: Gestational diabetes (GDM) has long-term consequences for the offspring. Sirtuins (SIRTs) are associated with vascular and metabolic functions. We studied the impact of GDM on SIRT activity and expression in fetal endothelial colony-forming cells (ECFCs) and human umbilical vein endothelial cells (HUVECs) from pregnancies complicated by GDM. Methods: ECFCs and HUVECs were isolated from cord and cord blood of 10 uncomplicated pregnancies (NPs) and 10 GDM pregnancies. Nicotinamidadenindinukleotid (NAD + ) concentration, SIRT1 and SIRT3 activity, transcription levels of SIRT1, SIRT3, and SIRT4, and protein levels of SIRT1, SIRT3, and SIRT4 were determined in vitro with or without SIRT activators resveratrol (RSV) and paeonol. results: Fetal ECFCs from GDM pregnancies showed a decreased NAD + concentration, reduced SIRT1 and SIRT3 activity, and lower transcription levels of SIRT1, SIRT3, and SIRT4. HUVECs from GDM pregnancies had decreased NAD + concentrations and transcription levels of SIRT1 and SIRT4. RSV markedly enhanced the expression and activity of SIRTs in ECFCs and HUVECs, while paeonol was active only in ECFCs. conclusion: A reduction of SIRT activity and expression in fetal endothelial cells provides potential mechanistic insights into the pathophysiology of long-term cardiovascular complications observed in the offspring of GDM pregnancies. SIRT activators can increase SIRT activity in ECFCs, which opens perspectives for new therapeutic targets. a dverse events during fetal life have been implicated to induce fetal programming, which can result in chronic diseases (1). Especially gestational diabetes (GDM) of the mother has been associated with cardiovascular disease, metabolic syndrome, and obesity during later life in the offspring (2,3). The pathophysiological processes responsible for these late complications are largely unknown.Sirtuins (SIRTs) are important regulators of aging and metabolic diseases (4,5). Mammalian SIRTs belong to the histone deacetylase class III family comprising seven members (SIRT1-7), which require Nicotinamidadenindinukleotid (NAD + ) for their enzymatic activity (6). SIRT1 downregulation has been observed in peripheral blood mononuclear cells of individuals with impaired glucose tolerance (7,8). SIRT1 is known to regulate vascular endothelial cell functions (9). Furthermore, in vitro and in vivo studies demonstrated that a reduction in the number of endothelial progenitor cells (EPCs) under hyperglycemia is associated with reduced SIRT1 levels and activity (8,10). Endothelial cells regulate vascular tone and are the first fetal cells exposed to maternal hyperglycemia.In recent years, it has become evident that SIRT1 is a key player of EPC dysfunction in insulin resistance and metabolic syndrome (7,10,11). Overexpression of endothelium-specific SIRT1 protects against endothelial dysfunction induced by a high-fat diet and hyperglycemia (12,13). Recently, resveratrol (RSV) and paeonol (2′-Hydroxy-4′-methoxyacetophenone) have been shown to activate SIRTs and thus c...
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