Search

Cardiac allograft vasculopathy (CAV) is a transplant pathology, limiting graft survival after heart transplantation. CAV arteries are surrounded by ectopic lymphoid structures (ELS) containing B cells and plasma cells. The aim of this study was to characterize the antigenic targets of antibodies produced in ELS. Coronary arteries and surrounding epicardial tissue from 56 transplant recipients were collected during autopsy. Immunofluorescence was used to identify antibody-producing plasma cells. Immunoglobulin levels in tissue lysates were measured by enzyme-linked immunosorbent assay and analyzed for donor-specific HLA antibodies by Luminex assay. Cytokine and receptor expression levels were quantified using quantitative polymerase chain reaction. Plasma cells in ELS were polyclonal and produced IgG and/or IgM antibodies. In epicardial tissue, IgG (p < 0.05) and IgM levels were higher in transplant patients with larger ELS than smaller ELS. In 4 of 21 (19%) patients with ELS, donor-specific HLA type II antibodies were detected locally. Cytokine and receptor expression (CXCR3, interferon γ and TGF-β) was higher in large ELS in the epicardial tissue than in other vessel wall layers, suggesting active recruitment and proliferation of T and B lymphocytes. ELS exhibited active plasma cells producing locally manufactured antibodies that, in some cases, were directed against the donor HLA, potentially mediating rejection with major consequences for the graft., (© Copyright 2016 The American Society of Transplantation and the American Society of Transplant Surgeons.)

The interest in the use of humanized mouse models for research topics like Graft versus Host Disease (GvHD), allograft studies and other studies to the human immune system is growing. The design of these models is still improving and enables even more complicated studies to these topics. For researchers it can be difficult to choose the best option from the current pool of available models. The decision will depend on which hypothesis needs to be tested, in which field of interest, and therefore 'the best model' will differ from one to another. In this review, we provide a guide to the most common available humanized mouse models, with regards to different mouse strains, transplantation material, transplantation techniques, pre- and post-conditioning and references to advantages and disadvantages. Also, an evaluation of experiences with humanized mouse models in studies on GvHD and allograft rejection is provided., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Background: In the heart elevated levels of TNFalpha can cause lethal heart failure, like Dilated Cardiomyopathy (DCM). The level of TNFalpha production is in part determined by promoter gene polymorphisms. We investigated whether the TNFalpha promoter gene polymorphism is in this way involved in the outcome of end-stage heart failure and predicts whether patients require left ventricular assist device (LVAD) support or can be kept on medical therapy (MT)while awaiting heart transplantation (HTx). As most patients in this study received a heart transplant, the role of the TNFalpha polymorphisms in transplant rejection was studied as well., Methods and Results: In twenty nine patients with DCM, 35 patients with Ischemic Heart Disease (IHD; both on MT), 26 patients on LVAD support and 61 cardiac transplant donors TNFalpha plasma level was detected by EASIA. In both patients groups high levels of TNFalpha plasma levels was observed however, in patients supported by LVAD this increase was much higher compared to patients on MT. Furthermore, this increase seems to be associated with the TNF 1 allele ('G' at position -308) instead of the TNF2 allele (A at position -308). The promoter polymorphisms at positions -238, -244 and -308 were observed by polymerase chain reaction and sequencing. Polymorphism at positions -238, -244 and -308 did not show any relevant differences between the groups. However, at position -308, a trend of a higher incidence of the TNF2 allele (an "A" at position -308) in DCM patients compared to donors was shown. The distribution of the TNF1 and TNF2 alleles was not different in patients on medical therapy compared to the patients supported by a LVAD. No association was found between patients' TNFalpha promoter gene polymorphism and rejection. However, patients that received a donor heart with the TNF2 allele developed more rejection episodes, compared to patients that received a donor heart with the TNF1 allele., Conclusion: TNFalpha levels are high in patients with end-stage heart failure on MT, but even higher in patients on LVAD support. These high TNFalpha plasma levels however, are not correlated with the TNF2 allele but seems to be associated with the TNF1 allele. Furthermore, in HTx the donor TNFalpha gene seem to play a more important role in severity of acute rejection than that of the patient.

Expression of interleukin (IL)-10 influences the frequency of rejection events after organ transplantation. Therefore, 70 heart transplant patients were genotyped for three single nucleotide polymorphisms and a microsatellite polymorphism in the promotor region of the IL-10 gene. The promoter region was amplified by polymerase chain reaction and genotyped by a colorometric oligo ligation assay and gene scan analysis, respectively. Patient groups consisted of patients suffering from dilated cardiomyopathy or ischaemic heart disease. Cardiac donors served as control group. No correlation was found between genotypes and heart failure or rejection after heart transplantation. This may indicate that in heart transplantation, the total balance of cytokine production is more important for post-transplant rejection activities than the levels of IL-10 as such.

The reduction in the frequency of rejection episodes several months after heart transplantation (HTX) correlates with the development of donor-specific nonresponsiveness. This is reflected in a reduced frequency of donor-specific cytotoxic T cells (CTL) in the peripheral blood. We investigated whether the reduced CTL frequency and the incidence of rejection episodes coincided with a change in the frequency of either IL-2- or IL-4-producing helper T lymphocytes (HTL). We measured the frequency of HTL before and at several time points after HTX in the blood of ten recipients, using limiting dilution analysis for IL-2 and IL-4. In most patients, HTL frequencies dropped immediately after transplantation, but returned to pre-HTX values later after transplantation. No consistent decrease or increase in frequencies was observed long after HTX. In contrast to IL-2, the HTL frequencies for IL-4 before transplantation were significantly higher in patients without post-HTX rejection episodes requiring treatment than in patients with such episodes. This phenomenon was observed for the in vitro responses towards both donor and third-party cells. In conclusion, relatively high frequencies of IL-4-producing T cells may have a beneficial effect on the outcome of human heart transplantation, because they are associated with a reduced incidence of rejection episodes after transplantation.

It is unclear whether the intracardial immune reactivity after heart transplantation influences the peripheral immunological status (activation or nonresponsiveness) of the patient. Co-stimulation and activation-induced cell death (AICD) or apoptosis play an important role in determining the balance between lymphocyte reactivity and nonreactivity. Therefore, we studied the expression of co-stimulatory molecules and the process of apoptosis in biopsies of human heart allografts, using immunohistochemistry. Although a normal expression of co-stimulatory molecules on antigen-presenting cells was observed, the expression of their counter-structures on T cells was absent. This may be due to chronic T cell activation, which can lead to the induction of apoptosis via the Fas/Fas ligand pathway. In the infiltrates, a considerable percentage of the lymphocytes, but not the macrophages, were apoptotic. Apoptosis was confirmed by DNA fragmentation analysis. Increased numbers of Bax-expressing versus decreased numbers of Bcl2-expressing lymphocytes in comparison with normal lymphoid tissue confirmed a imbalance in favor of apoptosis. Apoptosis was biased towards CD4+ T cells (65.7% versus 26.6% in CD8+ T cells). Fas was expressed on most of the infiltrating cells. Fas ligand expression was also observed, not only on most of the T cells but also on all macrophages. Because macrophages were often detected in close contact with T cells, they may play a role in T cell regulation via the Fas/Fas ligand pathway. This study indicates that, during rejection, not only is tissue damage induced by infiltrating T cells, but also the infiltrating lymphocytes themselves are actively down-regulated (eg, AICD) by one another and by macrophages in the infiltrate. This regulatory process may affect the immunological status of the patient after heart transplantation.