Blood dendritic cell levels and phenotypic characteristics in relation to etiology of end-stage heart failure: implications for dilated cardiomyopathy.

BACKGROUND: Dysregulation of dendritic cell (DC) mediated immune responses towards auto-antigens, is considered an important feature in the maintenance of experimentally induced heart failure (HF). In order to evaluate the role of blood DCs in cardiomyopathies of different origins, we examined myeloid (mDC) and plasmacytoid (pDC) subset levels and maturation characteristics, according to HF severity and etiology in humans. METHODS: Absolute numbers of mDCs and pDCs in 12 New York Heart Association (NYHA) class-II, 28 NYHA class III-IV HF patients and 18 healthy controls, were studied by 4-colour whole blood flow cytometry. RESULTS: End-stage (NYHA III-IV) HF patients had comparable circulating DC subset levels to NYHA-II patients and controls. However, within the NYHA III-IV group total DC levels in patients with non-ischemic dilated cardiomyopathy (DCM) were higher (P<0.001) than in patients with coronary artery disease (CAD), hypertrophic cardiomyopathy (HCM) or other HF etiology. This was due to a significant increase of primarily mDCs (P<0.0001) and to a lesser extent of pDCs (P<0.05) in idiopathic DCM patients, independent of systolic or diastolic cardiac dysfunction. Maturation marker CD83 and lymphoid homing chemokine receptor CCR7 surface expression was enhanced only on mDCs, but not pDCs from DCM patients (P<0.05), compared to patients with CAD, HCM or other underlying cardiac pathophysiology. CONCLUSIONS: Total blood DC levels in end-stage HF are elevated in patients with DCM. Whole blood DC characterisation may lead to new insights into the pathophysiology of idiopathic DCM in humans.

FTY720 treatment of kidney transplant patients: a differential effect on B cells, naïve T cells, memory T cells and NK cells.

FTY720 alters lymphocyte recirculation and homing by interfering with S1P receptors on lymphocytes, possibly in combination with chemokine receptors, and induces a decrease in PBL counts. In fresh, whole blood samples of 14 kidney transplant patients, we analyzed by flow cytometry the effect of FTY on the number of NK cells, monocytes, naïve (CCR7+) T cells, memory (CCR5+) T cells and B cells. Patients treated with 0.5, 2.5 or 5mg FTY/day showed a strong decrease in T and B cell numbers. NK cells and monocytes were not affected. FTY reduced primarily naïve T cells. From the memory T cells (CCR5+), predominantly CD8 cells, 40-60% remained in the circulation. The majority of the CCR7+ cells disappeared from the circulation within 3-6h, while a further reduction was achieved later. The more slowly decrease in naïve CCR7+ T cell numbers was also observed in the group treated with 0.25mg FTY/day. Elispot assays revealed no IL-4 producing cells and a low frequency of IFN-gamma producing cells. We suggest that both CCR7 dependent and independent mechanisms are involved in the depletion of T cells from peripheral blood.

Altered chemokine receptor profile on circulating leukocytes in human heart failure.

Chemokines and their receptors have been implicated in the pathogenesis of different forms of heart failure (HF). We examined CC- and CXC-chemokine receptor expression in fresh peripheral blood leukocyte populations from 24 end-stage HF patients consisting of coronary artery disease (CAD; n = 6) and hypertrophic cardiomyopathy (HCM; n = 7) or idiopathic dilated cardiomyopathy (IDCM; n = 8) or valvular disease (VD; n = 3) and compared the data with 18 healthy controls. Levels of CCR1, 2, 3, 4, 5, and 7, and CXCR1, 2, 3, and 4 were measured by flow cytometry, and the expression profile was assessed as molecules of equivalent soluble fluorochrome units as well as frequency (percentage) of CD3+, CD4+, and CD8+ T cells and monocytes or granulocytes. Frequency of CD3+ CXCR4+, CD3+ CXCR1+, and CD3+ CXCR3+ cells was significantly increased in HF patients, whereas only CCR7 and CXCR4 expression levels were elevated on CD3+ cells. Both CD4+ CXCR4+ and CD8+ CXCR4+ cell frequencies were significantly increased irrespective of cardiac disease etiology. Elevated CCR7 expression was less pronounced on CD4+ than CD8+ cells in patients with CAD and IDCM. Expression of CXCR4 on CD8+ cells was upregulated substantially, regardless of the cause of disease. CD8+ CXCR1+ and CD8+ CXCR3+ but not CD4+ CXCR1+ or CD4+ CXCR3+ cells were increased in the HF patients with IDCM and CAD, respectively. Expression of CXCR1 or CXCR3 on both CD4+ and CD8+ cells did not differ in all the groups. For monocytes, frequency of CD14+ CCR1+ and CD14+ CCR2+ cells was significantly decreased in CAD patients, whereas, increase in CD14+ CXCR4+ cell frequency was accompanied with elevated CXCR4 expression. On granulocytes, CXCR1 and CXCR2 receptors were downregulated in all patients, compared with controls. Our results suggest that the altered expression profile of CC- and CXC-chemokine receptors on circulating leukocyte populations involves enhanced activation of the immune system, perhaps as part of the pathogenic mechanisms in HF. Modulation of the chemokine network could offer interesting novel therapeutic modalities for end-stage HF.

Impaired circulating dendritic cell reconstitution identifies rejecting recipients after clinical heart transplantation independent of rejection therapy.

OBJECTIVE: Dendritic cell (DC) mediated allo-antigen presentation to host antigen specific T-lymphocytes initiates acute allograft rejection. We investigated peripheral blood DC (PBDC) incidence and DC subset reconstitution in relation to histological diagnosis of acute cellular rejection (AR) and administration of rejection therapy after clinical heart transplantation (post-HTx). METHODS: Venous blood from 20 HTx recipients under standard immunosuppression was collected during serial endomyocardial biopsy (EMB) prior to administration of rejection therapy in a 9-month follow-up post-HTx. Echocardiographic assessment of allograft function during EMB was performed to distinguish clinical necessity for rejection therapy within histologically rejecting patients (R). Myeloid (mDC) and plasmacytoid (pDC) subsets identified by flow-cytometry were analysed for different ISHLT rejection grades. Circulating PBDC incidence and mDC/pDC ratio were compared sequentially between non-rejecting (NR) recipients and R patients treated (3A(+)) or not-treated (3A(-)) with rejection therapy during follow-up. RESULTS: Eleven samples from biopsy-proven AR episodes (AR(+): ISHLT>or=3) were compared to 89 samples from non-rejection episodes (AR(-): ISHLT grade 0, n=52; grade 1, n=29; grade 2, n=8). We observed an inverse correlation of mDCs (P<0.05) but not pDCs with increasing rejection grade. PBDC incidence and mDC/pDC ratio were low in blood samples obtained during AR (P<0.05 and P<0.01, respectively). Both PBDCs and mDC/pDC ratio decreased during each AR episode (P<0.05). Comparison of 3A(+) and 3A(-) rejectors with NR patients after 12 weeks post-HTx revealed lower PBDC incidence (P<0.01) and mDC/pDC ratio (P<0.05) for R patients, independent of rejection therapy. CONCLUSIONS: Defective DC subset reconstitution by dendritic cell profiling identifies patients at risk for AR after 3 months post-HTx. This finding may contribute to further optimization of immunosuppressive treatment strategies after clinical heart transplantation.

Preferential depletion of blood myeloid dendritic cells during acute cardiac allograft rejection under controlled immunosuppression.

Allo-Ag presentation to Ag-specific T-lymphocytes by donor or recipient dendritic cells (DCs) induces acute rejection (AR) after solid organ transplantation. It is postulated that myeloid (mDC) and plasmacytoid (pDC) subsets circulate differentially between bone marrow, heart and lymphoid tissues after cardiac transplantation (HTx). We investigated peripheral blood DC subset distribution, maturation and lymphoid homing properties in relation to endomyocardial biopsy (EMB) rejection grade after clinical HTx. Twenty-one HTx recipients under standard immunosuppression were studied in a 9-month follow-up. mDC and pDC numbers were analyzed by flow cytometry in fresh venous whole blood samples collected during the EMB procedures and before histological diagnosis of AR. Subsets were further characterized for maturation marker CD83 and lymphoid homing chemokine receptor CCR7. Although numbers of both DC subsets remained low for the whole post-HTx period, we observed a negative association of mDCs with rejection grade. Repeated measurements analysis revealed that only mDCs decreased during AR episodes. Rejectors had lower mDC numbers after a 3-month follow-up compared to nonrejectors. Furthermore, patients during AR exhibited low proportions of mDCs positive for CD83 or CCR7. These findings suggest peripheral blood mDC depletion in association with selective lymphoid homing of this subset during AR after clinical HTx.

Vitamin E-coated dialyzer membranes downregulate expression of monocyte adhesion and co-stimulatory molecules.

BACKGROUND: In patients on chronic hemodialysis leukocyte activation has been related to the impaired function of the immune system. In this study we investigated if the vitamin E-coated dialyzer membrane could reduce monocyte activation thereby improving cellular immunity. METHODS: This hypothesis was tested in a prospective crossover trial in which 14 stable hemodialysis patients were switched from the baseline hemophane dialyzer to a vitamin E-coated and thereafter a polysulphone dialyzer membrane or vice versa. RESULTS: Monocyte MHC class I, CD54 and ICAM-1 expression was significantly downregulated when a vitamin E-coated or polysulphone dialyzer was used. The use of a vitamin E membrane specifically decreased monocyte CD40 and CD86 expression. Lectin induced T cell proliferation increased with the use of the vitamin E-coated membrane as compared to polysulphone and hemophane dialyzers. CONCLUSION: Vitamin E-coated dialyzers induced a less-activated phenotype of monocytes and may improve cellular immunity.

Peripheral blood dendritic cells and GM-CSF as an adjuvant for hepatitis B vaccination in hemodialysis patients.

BACKGROUND: Dysfunctional antigen presentation may underlie the impaired antibody response to hepatitis B vaccination in hemodialysis patients. Dendritic cells are considered to be the most important antigen presenting cells, but their presence and function in hemodialysis patients is unclear. Granulocyte-monocyte-colony stimulating factor (GM-CSF) has been given successfully to hemodialysis patients to increase the proportion of responders to hepatitis B vaccination. Although GM-CSF acts on both monocytes and dendritic cells, the mechanisms underlying its adjuvant quality are largely unknown. METHODS: In this study we analyzed monocytes and dendritic cells in the peripheral blood of hemodialysis patient that had responded to a standard hepatitis B vaccination procedure (responders), patients who had not responded (nonresponders), and healthy controls. The nonresponders were given two additional booster vaccines, both preceded by administration of GM-CSF the day before. RESULTS: After two booster vaccinations with GM-CSF, six out of seven patients developed a protective antibody response to hepatitis B. The memory T-cell response to tetanus toxoid was significantly lower in nonresponders compared to controls. The monocytes of dialysis patients and healthy controls showed a similar expression of relevant cell surface molecules. However, the numbers of circulating dendritic cells were on average 50% reduced compared to healthy controls, with a further reduction after GM-CSF administration. This was accompanied by a decrease of T-cell proliferation in antigen presentation assays. Monocytes showed increased major histocompatibility complex (MHC) class II, CD54, and CD40 expression, while their antigen-presenting capacity remained unchanged. CONCLUSION: GM-CSF is an effective adjuvant for hepatitis B vaccination in primary nonresponding hemodialysis patients, but paradoxically decreases the antigen presenting capacity of peripheral blood mononuclear cells and the number of circulating dendritic cells.

Peripheral blood dendritic cells in human end-stage heart failure and the early post-transplant period: evidence for systemic Th1 immune responses.

OBJECTIVES: Dendritic cells (DCs) are antigen presenting cells that play a central role in inflammation, allograft rejection and immune tolerance. Myeloid (mDC) and plasmacytoid (pDC) subsets regulate immune reactions by polarising naive T-helper cells into a Th1 or Th2 response, respectively. In this study we examined total peripheral blood DCs, mDC and pDC subsets in chronic heart failure (CHF) and clinical heart transplantation (HTx). METHODS: We compared 16 heart transplant patients before and after HTx to 14 healthy controls. Whole blood was collected pre-HTx and 1-week post-HTx from patients and at corresponding time-points from controls. All patients received induction and maintenance immunosuppression post-HTx. mDCs and pDCs were measured by flow cytometry and were further characterised for maturation and homing potential to the secondary lymphoid organs with CD83 and CCR7, respectively. Data were expressed as absolute numbers/microl whole blood, percentage (%) mDC or pDC of total blood DCs and % positive DCs for CD83 and CCR7. RESULTS: CHF patients had more peripheral blood DCs compared to controls (P<0.01) while only the mDC fraction was increased compared to controls (P=0.01). Percentage CD83(+) and CCR7(+) mDCs was also higher than control levels (P<0.05). One week post-HTx, total DCs, mDCs and pDCs decreased below controls (P<0.001). At the same time % mDCs in peripheral blood increased markedly compared to CHF and control levels (P<0.001). The %CD83(+) mDC, %CD83(+) pDC and %CCR7(+) mDC also returned to control levels and only %CCR7(+) pDC decreased below control levels (P=0.005). CONCLUSIONS: Total peripheral blood DCs are elevated during CHF due to an increase in the mature fraction of the mDC subset suggesting a possible Th1 response in end-stage heart failure. The decrease in total DCs and mature mDCs and pDCs seen post-HTx, probably reflects immunological quiescence through adequate immunosuppression. Peripheral blood DC monitoring may provide a new insight into mechanisms of heart failure and allograft rejection by safe weaning from immunosuppression after clinical HTx.

Frequencies of donor-reactive helper T lymphocytes correlate with rejection of aortic valve allografts in rats.

BACKGROUND AND AIMS OF THE STUDY: Human valve allografts are commonly used in cardiac surgery for congenital and acquired valve diseases. Particularly in the pediatric population, these allografts are prone to fail in the long term, and require replacement. In part, this failure may be due to immunological phenomena. The frequency of helper T lymphocytes (HTLf) measured in peripheral blood and spleen serves as a parameter for acute rejection in organ transplantation. The value of this parameter in valve transplantation was studied using the 'Rotterdam' implantation model in rats. METHODS: HTLf were determined in peripheral blood and spleen at seven and 21 days after allogeneic (WAG-->DA) and syngeneic (DA-->DA) implantation of an aortic valved conduit. Valve competence was tested pre-implantation, at days 7 and 21 after implantation, and after explantation using a retrograde saline injection. Explanted valves were examined histologically. RESULTS: At seven days after allogeneic valve transplantation, HTLf in spleen (median 71/10(6)), but not in peripheral blood (median 26/106) were significantly elevated. At 21 days after allogeneic transplantation, a significant increase in HTLf was seen in both peripheral blood (median 10(9)/10(6)) and spleen (median 92/10(6)). All five (100%) syngeneic grafts and five of seven (71%) allografts were competent at day 7. At day 21, all five syngeneic grafts (100%) and zero allografts (0%) remained competent (p = 0.01). Histologically, mononuclear cell infiltration into the allogeneic valve leaflets and in the vascular wall was observed at day 7. At day 21, valve leaflets appeared to be acellular and deformed. All syngeneic valve grafts retained normal morphology. CONCLUSION: After aortic valve allografting in the rat, HTLf correlate with valve dysfunction and histopathological signs of rejection. Therefore, HTLf-analysis may be a useful tool in monitoring the cellular immune response as an indicator for early graft dysfunction due to rejection in clinical valve transplantation.