The mechanisms by which T cells contribute to the hepatic inflammation during antigen-independent ischemia/reperfusion (I/R) are not fully understood. We analyzed the recruitment of T cells in the postischemic hepatic microcirculation in vivo and tested the hypothesis that T cells interact with platelets and activate sinusoidal endothelial cells, resulting in microvascular dysfunction followed by tissue injury. Using intravital videofluorescence microscopy, we show in mice that warm hepatic I/R (90/30-140 min) induces accumulation and transendothelial migration of CD4+, but not CD8+ T cells in sinusoids during early reperfusion. Simultaneous visualization of fluorescence-labeled CD4+ T cells and platelets showed that approximately 30% of all accumulated CD4+ T cells were colocalized with platelets, suggesting an interaction between both cell types. Although interactions of CD4+/CD40L-/- T cells with CD40L-/- platelets in wild-type mice were slightly reduced, they were almost absent if CD4+ T cells and platelets were from CD62P-/- mice. CD4 deficiency as well as CD40-CD40L and CD28-B7 disruption attenuated postischemic platelet adherence in the same manner as platelet inactivation with a glycoprotein IIb/IIIa antagonist and reduced neutrophil transmigration, sinusoidal perfusion failure, and transaminase activities. Treatment with an MHC class II antibody, however, did not affect I/R injury. In conclusion, we describe the type, kinetic, and microvascular localization of T cell recruitment in the postischemic liver. CD4+ T cells interact with platelets in postischemic sinusoids, and this interaction is mediated by platelet CD62P. CD4+ T cells activate endothelium, increase I/R-induced platelet adherence and neutrophil migration via CD40-CD40L and CD28-B7-dependent pathways, and aggravate microvascular/hepatocellular injury.
"It has been previously demonstrated that use of MHC-II-blocking antibodies has no effect on serum alanine transaminase following hepatic IR, which suggested that T cells play a role not involving the αβ TCR and that lymphocyte actions occur through a non-antigenic mechanism . Furthermore, non-naïve as well as unconventional T cells can be functionally activated by cytokines in a manner independent of TCR engagement , . "
[Show abstract][Hide abstract] ABSTRACT: BackgroundCD4+ T cell is acknowledged as a key factor in the initiation phase of liver ischemia reperfusion injury. The purpose of current study is to demonstrate the effect of antecedent near-term anti-CD25 monoclonal antibody treatment on IR-induced liver injury by modulation of CD4+ T cells.Methods70% liver warm IR was induced in male C57BL/6 mice after anti-CD25 mAb or non-specific IgG administration. Liver function, histological damage, in
vitro Proliferation, FACS, cytokine production, and immunofluorescence were assessed to evaluate the impact of antecedent near-term PC61 treatment on IR-induced liver injury.ResultsAfter 70% liver ischemia, mice preconditioned with PC61 displayed significantly preserved liver function as characterized by less histological damage and reduced serum enzymes level. Mechanistic studies revealed that the protection effect of anti-CD25 mAb was associated with ameliorated intrahepatic inflammatory milieu and reduced CD4+ T lymphocytes as manifested by the decrease of proinflammatory cytokine production (less expression of TNF-α, IFN-γ, IL-2, and IL-6) and the lower CD4/CD8 proportion.ConclusionsOur results provide first line of evidence indicating that near-term treatment with anti-CD25 monoclonal antibody might provide protection for livers against IR-induced injury by reducing CD4+ T cells, but not influencing functional Treg population. Therefore, our results demonstrate a potential function of anti-CD25 monoclonal antibody which was neglected in the past, and may be helpful in various clinical conditions, particularly in liver and kidney transplantations.
PLoS ONE 09/2014; 9(9):e106892. DOI:10.1371/journal.pone.0106892 · 3.23 Impact Factor
"In this respect, T cells have been shown to be critically involved in the induction of IRI of the liver
[29-32]. A rapid recruitment of CD4+ T cells in hepatic sinusoids as early as 30 minutes after reperfusion is followed by their migration through the endothelial barrier to injured hepatic tissue
. Although CD4+ T cells themselves are not cytotoxic, they release a panel of cytokines, chemokines and adhesion molecules which are potentially harmful to the organ. "
[Show abstract][Hide abstract] ABSTRACT: Background:
Critical organ shortage results in the utilization of extended donor criteria (EDC) liver grafts. These marginal liver grafts are prone to increased ischemia reperfusion injury (IRI) which may contribute to deteriorated graft function and survival. Experimental data have shown that the calcineurin inhibitor tacrolimus exerts protective effects on hepatic IRI when applied intravenously or directly as a hepatic rinse. Therefore, the aim of the present study is to examine the effects of an ex vivo tacrolimus perfusion on IRI in transplantation of EDC liver grafts.
The TOP-Study (tacrolimus organ perfusion) is a randomized multicenter trial comparing the ex vivo tacrolimus perfusion of marginal liver grafts with placebo. We hypothesize that a tacrolimus rinse reduces IRI, potentially improving organ survival following transplantation of EDC livers. The study includes livers with two or more EDC, according to Eurotransplant International Foundation's definition of EDC livers. Prior to implantation, livers randomized to the treatment group are rinsed with tacrolimus at a concentration of 20 ng/ml in 1000 ml Custodiol solution and in the placebo group with Custodiol alone. The primary endpoint is the maximum serum alanine transamninase (ALT) level within the first 48 hours after surgery; however, the study design also includes a 1-year observation period following transplantation. The TOP-Study is an investigator-initiated trial sponsored by the University of Munich Hospital. Seven other German transplant centers are participating (Berlin, Frankfurt, Heidelberg, Mainz, Münster, Regensburg, Tübingen) and aim to include a total of 86 patients.
Tacrolimus organ perfusion represents a promising strategy to reduce hepatic IRI following the transplantation of marginal liver grafts. This treatment may help to improve the function of EDC grafts and therefore safely expand the donor pool in light of critical organ shortage.
EudraCT number: 2010-021333-31, ClinicalTrials.gov identifier: NCT01564095.
"Activated NKT cells directly damage liver tissue and also produce IFN-γ with further activation of KC and hepatocytes [69, 70]. The net result of this circular activation and stimulation of different cell sub types is destruction of hepatocytes and SEC [71, 72]. "
[Show abstract][Hide abstract] ABSTRACT: Liver ischemia/reperfusion (IR) injury is caused by a heavily toothed network of interactions of cells of the immune system, cytokine production, and reduced microcirculatory blood flow in the liver. These complex networks are further elaborated by multiple intracellular pathways activated by cytokines, chemokines, and danger-associated molecular patterns. Furthermore, intracellular ionic disturbances and especially mitochondrial disorders play an important role leading to apoptosis and necrosis of hepatocytes in IR injury. Overall, enhanced production of reactive oxygen species, found very early in IR injury, plays an important role in liver tissue damage at several points within these complex networks. Many contributors to IR injury are only incompletely understood so far. This paper tempts to give an overview of the different mechanisms involved in the formation of IR injury. Only by further elucidation of these complex mechanisms IR injury can be understood and possible therapeutic strategies can be improved or be developed.
HPB Surgery 05/2012; 2012(3):176723. DOI:10.1155/2012/176723
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