Specific recruitment of CD4+CD25++ regulatory T cells into the allograft in heart transplant recipients

Human Parvovirus B19 (B19V) Up-regulates CXCR4 Surface Expression of Circulating Angiogenic Cells: Implications for Cardiac Ischemia in B19V Cardiomyopathy

Background

Human parvovirus B19 (B19V) infection and damage of circulating angiogenic cells (CAC) results in dysfunctional endogenous vascular repair (DEVR) with secondary end-organ damage. Trafficking of CAC is regulated by SDF-1α and the respective receptor CXCR4. We thus tested the hypothesis of a deregulated CXCR4/SDF-1α axis in symptomatic B19V-cardiomyopathy.

Methods

CAC were infected in vitro with B19V and transfected with B19V-components. Read-out were: CXCR4-expression and migratory capacity at increasing doses of SDF-1α. In 31 patients with chronic B19V-cardiomyopathy compared to 20 controls read-outs were from blood: migratory capacity, CXCR4 expression on CAC, serum SDF-1α; from cardiac biopsies: SDF-1α mRNA, HIF-1α mRNA, microvascular density, resident cardiac stem cells (CSC), transcardiac gradients of CAC.

Results

In vitro B19V-infected CAC showed up-regulation of surface CXCR4 with increased migratory capacity further enhanced by elevated SDF-1α concentrations. Overexpression of the B19V capsid protein VP2 was associated with this effect. Chronic B19V-cardiomyopathy patients showed increased numbers of ischaemia mobilised CAC but DEVR as well as diminished numbers of CAC after transcardiac passage. Cardiac microvascular density and CSC were significantly reduced in B19V-cardiomyopathy.

Conclusions

We thus conclude that B19V infection has a direct VP2-mediated negative impact on trafficking of CAC in the presence of impaired cardiac regeneration.

Regulatory T-Cell Levels in the Longest Surviving Asian Patient After Heart-Lung Transplant

Heart-lung transplant is the most effective therapy for patients with end-stage cardiopulmonary disease. Here, we report an initial assessment of a 31-year-old man who had survived more than 11 years after heart-lung transplant, which represents the longest survival time in this procedure in Asian studies. At his 11th anniversary after transplant, extensive tests were carried out, especially to detect regulatory T-cell levels for the first time in a surviving heart-lung transplant recipient. Preliminarily data revealed the status of his immunologic function in relation to chronic allograft rejection. All data indicated that the patient was in good condition. This is the first study detecting regulatory T-cell levels in a heart-lung transplant patient.

Cardiac migration of endogenous mesenchymal stromal cells in patients with inflammatory cardiomyopathy

Introduction. Mesenchymal stromal cells (MSC) have immunomodulatory features. The aim of this study was to investigate the migration and homing potential of endogenous circulating MSC in virus negative inflammatory cardiomyopathy (CMi). Methods. In 29 patients with (n = 23) or without (n = 6) CMi undergoing endomyocardial biopsies (EMB), transcardiac gradients (TCGs) of circulating MSC were measured by flow cytometry from blood simultaneously sampled from aorta and coronary sinus. The presence of MSC in EMB, cardiac inflammation, and SDF-1α mRNA expression were detected via immunohistochemistry and real-time PCR. Results. MSC defined as CD45⁻CD34⁻CD11b⁻CD73⁺CD90⁺ cells accounted for 0.010 [0.0025–0.048]%/peripheral mononuclear cell (PMNC) and as CD45⁻CD34⁻CD11b⁻CD73⁺CD105⁺ cells for 0.019 [0.0026–0.067]%/PMNC, both with similar counts in patients with or without cardiac inflammation. There was a 29.9% (P < 0.01) transcardiac reduction of circulating MSC in patients with CMi, correlating with the extent of cardiac inflammation (P < 0.05, multivariate analysis). A strong correlation was found between the TCG of circulating MSC and numbers of MSC (CD45⁻CD34⁻CD90⁺CD105⁺) in EMB (r = −0.73, P < 0.005). SDF-1α was the strongest predictor for increased MSC in EMB (P < 0.005, multivariate analysis). Conclusions. Endogenous MSC continuously migrate to the heart in patients with CMi triggered by cardiac inflammation.

Thoracic organ transplantation: laboratory methods

Although great progress has been achieved in thoracic organ transplantation through the development of effective immunosuppression, there is still significant risk of rejection during the early post-transplant period, creating a need for routine monitoring for both acute antibody and cellular mediated rejection. The currently available multiplexed, microbead assays utilizing solubilized HLA antigens afford the capability of sensitive detection and identification of HLA and non-HLA specific antibodies. These assays are being used to assess the relative strength of donor specific antibodies; to permit performance of virtual crossmatches which can reduce the waiting time to transplantation; to monitor antibody levels during desensitization; and for heart transplants to monitor antibodies post-transplant. For cell mediated immune responses, the recent development of gene expression profiling has allowed noninvasive monitoring of heart transplant recipients yielding predictive values for acute cellular rejection. T cell immune monitoring in heart and lung transplant recipients has allowed individual tailoring of immunosuppression, particularly to minimize risk of infection. While the current antibody and cellular laboratory techniques have enhanced the ability to manage thoracic organ transplant recipients, future developments from improved understanding of microchimerism and graft tolerance may allow more refined allograft monitoring techniques.

Expression of circulatory dendritic cells and regulatory T-cells in patients with different subsets of coronary artery disease

BACKGROUND

Dendritic cells (DCs), regulators of innate and adaptive immunity, may play an important role in atherosclerosis. DC invasion was found in early atherosclerotic lesions. We aimed to characterize circulating DC gene expression in patients with different subsets of coronary artery disease (CAD).

METHODS

Peripheral blood mononuclear cells were quantified using real-time polymerase chain reaction and fluorescence activated cell sorting in patients with acute coronary syndrome (ST-elevation myocardial infarction [STEMI], n = 35; non-ST-elevation myocardial infarction [NSTEMI], n = 30) and stable CAD (6 months after stent implantation without progression, n = 15) compared with control subjects (n = 15). DCs and T-cells (TCs) were characterized using specific primers for CD1a (immature), CD86 (mature), CD123 (plasmacytoid), BDCA1 (myeloid), CD178 (activated TCs), and FOXP3 (regulatory TCs). To evaluate whether serum of patients with STEMI induces DC differentiation, incubation of patient serum was performed.

RESULTS

CD86 was upregulated and CD1a downregulated in all patients with CAD (P < 0.05). Patients with STEMI and NSTEMI showed a downregulation of CD1a compared with patients with stable CAD (P ≤ 0.01). In contrast, stable patients with CAD had elevated CD178 levels compared with patients with STEMI and NSTEMI (P ≤ 0.04). In patients with STEMI, FOXP3 was downregulated compared with control subjects (P < 0.0001). Incubation of STEMI serum induced an upregulation of CD1a and CD86 in a human DC cell line. Coincubation with a blocking antibody for heat shock protein 60 inhibited this upregulation.

CONCLUSIONS

DCs are differentially regulated in patients with different subsets of CAD. Mature DCs are upregulated and immature DCs are downregulated in patients with CAD. Patients with STEMI show a significant downregulation of regulatory TCs. Circulating shock protein 60 induces DC differentiation in patients with STEMI.

Reduced levels of both circulating CD4+ CD25+ CD127(low/neg) and CD4+ CD8(neg) invariant natural killer regulatory T cells in stable heart transplant recipients

A cross-regulation between two regulatory T cell (T(reg) ) subsets [CD4(+) CD25(+) and invariant natural killer (NK) T - iNK T] has been described to be important for allograft tolerance induction. However, few studies have evaluated these cellular subsets in stable recipients as correlates of favourable clinical outcome after heart transplantation. T(reg) and iNK T cell levels were assayed by flow cytometry in peripheral blood samples from 44 heart transplant recipients at a 2-year interval in 38 patients, and related to clinical outcome. Multi-parameter flow cytometry used CD4/CD25/CD127 labelling to best identify T(reg) , and a standard CD3/CD4/CD8/Vα24/Vβ11 labelling strategy to appreciate the proportions of iNK T cells. Both subtypes of potentially tolerogenic cells were found to be decreased in stable heart transplant recipients, with similar or further decreased levels after 2 years. Interestingly, the patient who presented with several rejection-suggesting incidents over this period displayed a greater than twofold increase of both cell subsets. These results suggest that CD4(+) CD25(+) CD127(low/neg) T(reg) and iNK T cells could be involved in the local control of organ rejection, by modulating immune responses in situ, in clinically stable patients. The measurement of these cell subsets in peripheral blood could be useful for non-invasive monitoring of heart transplant recipients, especially in the growing context of tolerance-induction trials.

Peripheral blood T regulatory cell counts may not predict transplant rejection

Background

Recent evidence shows that allograft survival rates show a positive correlation with the number of circulating T regulatory cells (Tregs). This study investigated both the number and the cytokine profiles exhibited by Foxp3⁺ Tregs in blood, spleen and lymph nodes of Lewis rat recipients of BN rat cardiac allografts after a single-dose of Rapamycin (RAPA).

Results

Rats were divided into three groups: control group (containing healthy control and acute rejection group), and recipients treated with a single dose of RAPA on either Day 1 (1D group)or Day 3 (3D group) post-transplant. We analyzed the number of Foxp3+Tregs and the expression of Foxp3 and cytokines in the peripheral blood and the peripheral lymphoid tissues. No difference was found in the numbers of circulating Foxp3+ Tregs between these three groups. RAPA administration significantly increased Foxp3 expression in peripheral lymphoid tissues after a single dose of RAPA on Day 3 post-transplant. Foxp3+Tregs inhibited the activity of effector T cells (T_eff) via the secretion of TGF-β1.

Conclusion

The number of Tregs in the recipient's blood may not be a good predictor of transplant rejection. Foxp3+Tregs inhibit the activity of T_eff cells mainly in the peripheral lymphoid tissues.

Immunosuppression in cardiac graft rejection: a human in vitro model to study the potential use of new immunomodulatory drugs

CXCL10-CXCR3 axis plays a pivotal role in cardiac allograft rejection, so that targeting CXCL10 without inducing generalized immunosuppression may be of therapeutic significance in allotransplantation. Since the role of resident cells in cardiac rejection is still unclear, we aimed to establish reliable human cardiomyocyte cultures to investigate Th1 cytokine-mediated response in allograft rejection. We used human fetal cardiomyocytes (Hfcm) isolated from fetal hearts, obtained after legal abortions. Hfcm expressed specific cardiac lineage markers, specific cardiac structural proteins, typical cardiac currents and generated ventricular action potentials. Thus, Hfcm represent a reliable in vitro tool for allograft rejection research, since they resemble the features of mature cells. Hfcm secreted CXCL10 in response to IFNgamma and TNFalphaalpha; this effect was magnified by cytokine combination. Cytokine synergy was associated to a significant TNFalpha-induced up-regulation of IFNgammaR. The response of Hfcm to some currently used immunosuppressive drugs compared to rosiglitazone, a peroxisome proliferator-activated receptor gamma agonist and Th1-mediated response inhibitor, was also evaluated. Only micophenolic acid and rosiglitazone halved CXCL10 secretion by Hfcm. Given the pivotal role of IFNgamma-induced chemokines in Th1-mediated allograft rejection, these preliminary results suggest that the combined effects of immunosuppressive agents and rosiglitazone could be potentially beneficial to patients receiving heart transplants.

Histone deacetylase inhibitors and transplantation

Simply detecting the presence or absence of Foxp3, a transcription factor characteristic of naturally occurring CD4+ CD25+ regulatory T cells (Tregs), now appears of minimal value in predicting the outcome of immunologic responses, since dividing human CD4+ effector T cells can induce Foxp3 without attaining repressive functions, and additional molecular interactions, as well epigenetic events, affect Foxp3-dependent Treg functions in humans and mice. Experimentally, in vivo and in vitro studies show histone deacetylase inhibitors (HDACi) can enhance the numbers and suppressive function of regulatory T cells (Tregs) by promoting Foxp3+ cell production, enhancing chromatin remodeling within Tregs, and inducing acetylation of Foxp3 protein itself. Human studies consistent with a role for HDACi in controlling Fox3-dependent Treg functions are also available. We review these molecular interactions and how they may be exploited therapeutically to enhance Treg-dependent functions, including post-transplantation.