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Post-transplant cytomegalovirus (CMV) infections and increased viral replication are associated with CMV-specific T-cell anergy. In the ATHENA-study, de-novo everolimus (EVR) with reduced-exposure tacrolimus (TAC) or cyclosporine (CyA) showed significant benefit in preventing CMV infections in renal transplant recipients as compared to standard TAC + mycophenolic acid (MPA). However, immunomodulatory mechanisms for this effect remain largely unknown. Ninety patients from the ATHENA-study completing the 12-month visit on-treatment (EVR + TAC n = 28; EVR + CyA n = 19; MPA + TAC n = 43) were included in a posthoc analysis. Total lymphocyte subpopulations were quantified. CMV-specific CD4 T cells were determined after stimulation with CMV-antigen, and cytokine-profiles and various T-cell anergy markers were analyzed using flow cytometry. While 25.6% of MPA + TAC-treated patients had CMV-infections, no such events were reported in EVR-treated patients. Absolute numbers of lymphocyte subpopulations were comparable between arms, whereas the percentage of regulatory T cells was significantly higher with EVR + CyA versus MPA + TAC (p = 0.019). Despite similar percentages of CMV-specific T cells, their median expression of CTLA-4 and PD-1 was lower with EVR + TAC (p < 0.05 for both) or EVR + CyA (p = 0.045 for CTLA-4) compared with MPA + TAC. Moreover, mean percentages of multifunctional CMV-specific T cells were higher with EVR + TAC (27.2%) and EVR + CyA (29.4%) than with MPA + TAC (19.0%). In conclusion, EVR-treated patients retained CMV-specific T-cell functionality, which may contribute to enhanced protection against CMV infections., (© 2020 The Authors. European Journal of Immunology published by Wiley-VCH GmbH.)

Background: After kidney transplantation, uncontrolled BK polyomavirus (BKPyV) replication causes kidney graft failure through BKPyV-associated nephropathy (BKPyVAN), but markers predicting outcome are missing. BKPyV-specific T cells may serve as a predictive marker to identify patients at risk of persistent DNAemia and BKPyVAN., Methods: Out of a total of 114 pediatric kidney recipients transplanted between 2008 and 2018, 36 children with posttransplant BKPyV-DNAemia were identified. In a prospective noninterventional study, BKPyV-specific CD4 and CD8 T cells were measured in 32 of 36 viremic pediatric kidney recipients using intracellular cytokine staining and flow cytometry. The course of the BKPyV replication was monitored with regard to duration of BKPyV-DNAemia and need of therapeutic intervention and diagnosis of proven BKPyVAN., Results: Levels of BKPyV-specific T cells negatively correlated with subsequent duration of BKPyV-DNAemia. Patients with BKPyV-specific CD4 T cells ≥0.5 cells/µL and/or BKPyV-specific CD8 T cells ≥0.1 cells/µL had transient, self-limiting DNAemia (PPV 1.0, NPV 0.86). BKPyV-specific CD4 and CD8 T cells below these thresholds were found in children with persistent BKPyV-DNAemia and biopsy-proven BKPyVAN with need for therapeutic intervention. After reducing immunosuppressive therapy, levels of BKPyV-specific CD4 T cells increased while plasma BKPyV-DNAemia declined., Conclusions: This study found that BKPyV-specific T cell levels may help to distinguish patients with transient, self-limiting BKPyV-DNAemia from those with persisting BKPyV-DNAemia and biopsy-proven BKPyVAN, who would benefit from individualized therapeutic interventions such as reduced immunosuppression. Thereby the risk for rejection because of unnecessary reduction of immunosuppression in case of self-limiting BKPyV-DNAemia can be minimized.

BACKGROUNDPatients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) differ in the severity of disease. We hypothesized that characteristics of SARS-CoV-2-specific immunity correlate with disease severity.METHODSIn this study, SARS-CoV-2-specific T cells and antibodies were characterized in uninfected controls and patients with different coronavirus disease 2019 (COVID-19) disease severity. SARS-CoV-2-specific T cells were flow cytometrically quantified after stimulation with SARS-CoV-2 peptide pools and analyzed for expression of cytokines (IFN-γ, IL-2, and TNF-α) and markers for activation, proliferation, and functional anergy. SARS-CoV-2-specific IgG and IgA antibodies were quantified using ELISA. Moreover, global characteristics of lymphocyte subpopulations were compared between patient groups and uninfected controls.RESULTSDespite severe lymphopenia affecting all major lymphocyte subpopulations, patients with severe disease mounted significantly higher levels of SARS-CoV-2-specific T cells as compared with convalescent individuals. SARS-CoV-2-specific CD4+ T cells dominated over CD8+ T cells and closely correlated with the number of plasmablasts and SARS-CoV-2-specific IgA and IgG levels. Unlike in convalescent patients, SARS-CoV-2-specific T cells in patients with severe disease showed marked alterations in phenotypical and functional properties, which also extended to CD4+ and CD8+ T cells in general.CONCLUSIONGiven the strong induction of specific immunity to control viral replication in patients with severe disease, the functionally altered characteristics may result from the need for contraction of specific and general immunity to counteract excessive immunopathology in the lung.FUNDINGThe study was supported by institutional funds to MS and in part by grants of Saarland University, the State of Saarland, and the Rolf M. Schwiete Stiftung.

Compliance of elite athletes with vaccination recommendations is low mainly based on concerns about side-effects and perceived poor vaccine efficacy due to continued physical training. We therefore employed seasonal influenza vaccination to investigate the effect of regular physical training on vaccine-induced cellular and humoral immunity in elite athletes and controls. Lymphocyte subpopulations and vaccine-specific T-cells were quantified and functionally characterized from 45 athletes and 25 controls before, and 1, 2 and 26 weeks after vaccination. Moreover, influenza-specific antibodies and their neutralizing function were quantified. Both groups showed a significant increase in vaccine-reactive CD4 T-cell levels which peaked one week after vaccination (p < 0.0001). The increase was significantly more pronounced in athletes (4.1-fold) compared to controls (2.3-fold; p = 0.0007). The cytokine profile changed from multifunctional T-cells co-producing IFNγ, IL-2 and TNFα to cells with restricted cytokine expression. This change in functionality was associated with a significant increase in CTLA-4 expression (p < 0.0001), which again was more pronounced in athletes. Likewise, the increase in neutralizing antibodies was stronger in athletes (p = 0.004 for H1N1; p = 0.032 for H3N2). In conclusion, both groups mounted a strong vaccine-specific cellular and humoral immunity after standard vaccination. The more pronounced increase in specific T-cells and neutralizing antibodies indicates that high frequency and intensity of training enhance vaccine-responses in elite athletes., (Copyright © 2019 Elsevier Inc. All rights reserved.)

NF-κB functions as modulator of T cell receptor-mediated signaling and transcriptional regulator of miR-34a. Our in silico analysis revealed that miR-34a impacts the NF-κB signalosome with miR-34a binding sites in 14 key members of the NF-κB signaling pathway. Functional analysis identified five target genes of miR-34a including PLCG1, CD3E, PIK3CB, TAB2, and NFΚBIA. Overexpression of miR-34a in CD4 + and CD8 + T cells led to a significant decrease of NFΚBIA as the most downstream cytoplasmic NF-κB member, a reduced cell surface abundance of TCRA and CD3E, and to a reduction of T cell killing capacity. Inhibition of miR-34a caused an increase of NFΚBIA, TCRA, and CD3E. Notably, activation of CD4 + and CD8 + T cells entrails a gradual increase of miR-34a. Our results lend further support to a model with miR-34a as a central NF-κB regulator in T cells.

In this approach, pre-stained cells from extrasanguinous fluids (ESFs) are stimulated in the presence of blood from the same individual. Thus, blood-derived antigen-presenting cells enable stimulation of both ESF- and blood T cells. Pre-staining allows distinction of T cells from ESF and blood, and simultaneous analysis of antigen-specific T cells in both compartments., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Background: Graft survival in transplant recipients depends on pharmacokinetics and on individual susceptibility towards immunosuppressive drugs. Nevertheless, pharmacodynamic changes in T-cell functionality in response to drugs and in relation to pharmacokinetics are poorly characterized. We therefore investigated the immunosuppressive effect of calcineurin inhibitors and steroids on general T-cell functionality after polyclonal stimulation of whole blood samples., Methods: General T-cell functionality in the absence or presence of immunosuppressive drugs was determined in vitro directly from whole blood based on cytokine induction after stimulation with the polyclonal stimulus Staphylococcus aureus enterotoxin B. In addition, diurnal changes in leukocyte and lymphocyte subsets, and on T-cell function after intake of immunosuppressive drugs were analyzed in 19 patients during one day and compared to respective kinetics in six immunocompetent controls. Statistical analysis was performed using non-parametric and parametric tests., Results: Susceptibility towards calcineurin inhibitors showed interindividual differences. When combined with steroids, tacrolimus led to more pronounced increase in the inhibitory activity as compared to cyclosporine A. While circadian alterations in leukocyte subpopulations and T-cell function in controls were related to endogenous cortisol levels, T-cell functionality in transplant recipients decreased after intake of the morning medication, which was more pronounced in patients with higher drug-dosages. Interestingly, calcineurin inhibitors differentially affected circadian rhythm of T-cell function, as patients on cyclosporine A showed a biphasic decrease in T-cell reactivity after drug-intake in the morning and evening, whereas T-cell reactivity in patients on tacrolimus remained rather stable., Conclusions: The whole blood assay allows assessment of the inhibitory activity of immunosuppressive drugs in clinically relevant concentrations. Circadian alterations in T-cell function are determined by dose and type of immunosuppressive drugs and show distinct differences between cyclosporine A and tacrolimus. In future these findings may have practical implications to estimate the net immunosuppressive effect of a given drug-regimen that daily acts in an individual patient, and may contribute to individualize immunosuppression.

Background: After kidney transplantation, immunosuppressive therapy causes impaired cellular immune defense leading to an increased risk of viral complications. Trough level monitoring of immunosuppressants is insufficient to estimate the individual intensity of immunosuppression. We have already shown that virus-specific T cells (Tvis) correlate with control of virus replication as well as with the intensity of immunosuppression. The multicentre IVIST01-trial should prove that additional steering of immunosuppressive and antiviral therapy by Tvis levels leads to better graft function by avoidance of over-immunosuppression (for example, viral infections) and drug toxicity (for example, nephrotoxicity)., Methods/design: The IVIST-trial starts 4 weeks after transplantation. Sixty-four pediatric kidney recipients are randomized either to a non-intervention group that is only treated conservatively or to an intervention group with additional monitoring by Tvis. The randomization is stratified by centre and cytomegalovirus (CMV) prophylaxis. In both groups the immunosuppressive medication (cyclosporine A and everolimus) is adopted in the same target range of trough levels. In the non-intervention group the immunosuppressive therapy (cyclosporine A and everolimus) is only steered by classical trough level monitoring and the antiviral therapy of a CMV infection is performed according to a standard protocol. In contrast, in the intervention group the dose of immunosuppressants is individually adopted according to Tvis levels as a direct measure of the intensity of immunosuppression in addition to classical trough level monitoring. In case of CMV infection or reactivation the antiviral management is based on the individual CMV-specific immune defense assessed by the CMV-Tvis level. Primary endpoint of the study is the glomerular filtration rate 2 years after transplantation; secondary endpoints are the number and severity of viral infections and the incidence of side effects of immunosuppressive and antiviral drugs., Discussion: This IVIST01-trial will answer the question whether the new concept of steering immunosuppressive and antiviral therapy by Tvis levels leads to better future graft function. In terms of an effect-related drug monitoring, the study design aims to realize a personalization of immunosuppressive and antiviral management after transplantation. Based on the IVIST01-trial, immunomonitoring by Tvis might be incorporated into routine care after kidney transplantation., Trial Registration: EudraCT No: 2009-012436-32, ISRCTN89806912 (17 June 2009).

To investigate correlates for the well-known impaired response of haemodialysis-patients to a variety of recommended vaccinations, the induction of antigen-specific cellular and humoral immunity was characterised after influenza-vaccination in two following seasons where the identical vaccine-composition was used. Influenza-specific T-cells were flow-cytometrically characterised from whole blood of 24 healthy controls and 26 haemodialysis-patients by proliferation-assays, induction of IFN-γ and TNF-α, and maturation markers. Antibody-titres were quantified using ELISA and hemagglutination-inhibition test. Influenza-specific CD4 T-cells were recently activated CD45RO+/CD27+ Th1-cells. Specific T-cell frequencies significantly increased 1-2 weeks after the first vaccination in both controls (mean increase by 0.50±0.64%, max: 3.01%) and haemodialysis-patients (by 0.55±0.71%, max: 3.44%). Thereafter, T-cell levels continuously decreased to pre-vaccination levels within approximately 7 weeks, whereas antibody-titres were more stable over time. By 6 months, haemodialysis-patients had significantly lower precursor-frequencies of proliferating influenza-specific memory T-cells (p=0.006). In the following season, memory-maintenance in immunocompetent individuals led to a significantly less pronounced increase in cellular immunity after re-vaccination (by only 0.12±0.09%, p=0.003), whereas the vaccine induced a strong increase in a second group of vaccination-naïve controls. Of note, haemodialysis-patients responded like vaccination-naïve individuals, as they showed a strong increase in cellular immunity after re-vaccination that was as pronounced as in the year before. In conclusion, the less pronounced T-cell increase after re-vaccination in controls may indicate maintenance of sufficient immunological memory. In contrast, the more rapid loss of proliferating cells in haemodialysis-patients may represent a sign of relative immunodeficiency and contribute to an increased incidence of recurrent infectious complications., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

CMV-specific T cells may be detected and quantified after antigen-specific stimulation based on the induction of cytokines as a readout system. Secreted cytokines may be detected from the supernatant of stimulated cells using ELISA. Alternatively, antigen-specific cytokine-secreting cells may be enumerated using an ELISPOT assay. These assays generally rely on the detection of IFNγ and do not allow for a simultaneous assessment of several cytokines on a single cell basis. Here we describe a flow-cytometry based method to analyze CMV-specific CD4 T cells after specific stimulation with a whole antigen lysate. In this assay, cytokine secretion from stimulated cells is blocked by the addition of brefeldin A. Using a panel of fluorescently labeled antibodies, not only intracellularly accumulated cytokines but also phenotypical characteristics of specifically activated T cells may be quantified in a multiparameter staining approach.

Purpose: Circadian rhythms play an important role in modulating cellular immune responses. The present study was performed to characterise circadian variations in lymphocyte numbers and antigen-specific T-cell functionality in healthy individuals under physiological conditions., Methods: Blood leukocyte populations of six healthy volunteers were quantified over 24 h. In addition, antigen-specific T-cell functionality was analysed directly ex vivo from whole blood using flow cytometry based on intracellular cytokine induction after a 6-hour stimulation with adenovirus antigen and Staphylococcus aureus enterotoxin B (SEB), respectively., Results: T-cell numbers and reactivity were stable during daytime, whereas a significant increase was observed during late evening and early morning hours. The percentage of T cells reacting towards adenovirus antigen and SEB showed a 1.76 ± 0.55-fold (p = 0.0002) and a 1.42 ± 0.33-fold (p = 0.0002) increase, respectively. Dynamics in T-cell reactivity were independent of the mode of antigen stimulation and inversely correlated with plasma levels of endogenous cortisol. Interestingly, peak frequencies of reactive T cells occurred late in the evening and did not directly coincide with peak numbers of bulk T cells that were observed in the early morning hours., Conclusions: Taken together, our data reveal a circadian regulation of T-cell immune responses in the peripheral blood of humans under physiological conditions. This knowledge may be of practical consequence for the timing of blood sampling for functional T-cell assays as well as for immunosuppressive drug intake after organ transplantation, where T-cell function may be influenced not only by drug-mediated inhibition but also by circadian fluctuations in T-cell reactivity.

Genetically modified lymphoblastoid cell lines (LCL) have been shown to be an attractive alternative source of antigen-presenting cells for cancer vaccination in vitro. We tested their application in patients with pancreatic cancer in a phase I clinical trial. As a model tumor antigen, we selected the point-mutated (codon 12) Ki-Ras p21 oncogene (muRas) frequently (∼85%) present in pancreatic adenocarcinoma. Autologous LCLs were established in vitro by spontaneous outgrowth from peripheral blood lymphocytes of seven pancreatic carcinoma patients and were genetically modified with an episomal Epstein-Barr virus (EBV)-based expression vector to express muRas (muRas-LCL). Weekly vaccinations with subcutaneous injection of 5×10(6) muRas-LCL were done. In six of seven patients, therapeutic vaccination elicited a T-cell response with an increase in the frequency of muRas-specific precursor cytotoxic T lymphocytes in the peripheral blood and positive delayed-type hypersensitivity reactions at the injection site. Besides local reactions and flu-like symptoms, there were no signs of toxicity and no acute EBV infection, onset of EBV-associated lymphoma, or other severe complications. A clinical response (stable disease) was observed for a short time period (2-4 months) in four of seven patients (57%), mostly in earlier tumor stages. Our results indicate that LCL presenting genetically modified antigen represent a valuable and easily available tool for in vivo autologous tumor vaccination. LCL can be transfected with any known tumor antigen and therefore should be further clinically investigated.

Background: Serological analysis of the infection status with the human cytomegalovirus (CMV) may be inaccurate after transfusion of blood products due to the variable content of CMV-specific antibodies., Objectives: In this situation, analysis of cellular immunity may represent a more accurate parameter to assign the individual CMV-infection status. This hypothesis was assessed in a sequence of clinically defined events where a CMV-seronegative patient received human immunoglobulins before AB0 incompatible transplantation of a graft from his CMV-seropositive mother and developed CMV-primary infection thereafter., Study Design: Humoral immunity was analyzed using ELISA, and CMV-specific CD4 T-cells were flow-cytometrically quantified using intracellular cytokine staining after a 6 h-stimulation with a CMV-antigen lysate., Results: Prior to transplantation, both CMV-specific antibody-titers and T-cell frequencies were below detection limit. After plasma infusion, the patient was temporarily seropositive but remained T-cell negative indicating passive immunity. CMV-specific T-cells became stably detectable after graft-related primary infection, thereby confirming a truly positive infection status., Conclusion: This case provides an instructive proof of principle to show that CMV-specific CD4 T-cells may serve as an accurate marker to define the true CMV-infection status in situations where serological testing is limited by the presence of passively administered antibodies., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Background: Cytomegalovirus (CMV) seronegative recipients (R-) of kidney transplants (KT) from seropositive donors (D+) are at higher risk for CMV replication and ganciclovir(GCV)-resistance than CMV R(+). We hypothesized that low CMV-specific T-cell responses are associated with increased risk of CMV replication in R(+)-patients with D(+) or D(-) donors., Methods: We prospectively evaluated 73 consecutive KT-patients [48 R(+), 25 D(+)R(-)] undergoing routine testing for CMV replication as part of a preemptive strategy. We compared CMV-specific interferon-gamma (IFN-gamma) responses of CD4+CD3+ lymphocytes in peripheral blood mononuclear cells (PBMC) using three different antigen preparation (CMV-lysate, pp72- and pp65-overlapping peptide pools) using intracellular cytokine staining and flow cytometry., Results: Median CD4+ and CD8+T-cell responses to CMV-lysate, pp72- and pp65-overlapping peptide pools were lower in D(+)R(-) than in R(+)patients or in non-immunosuppressed donors. Comparing subpopulations we found that CMV-lysate favored CD4+- over CD8+-responses, whereas the reverse was observed for pp72, while pp65-CD4+- and -CD8+-responses were similar. Concurrent CMV replication in R(+)-patients was associated with significantly lower T-cell responses (pp65 median CD4+ 0.00% vs. 0.03%, p = 0.001; CD8+ 0.01% vs. 0.03%; p = 0.033). Receiver operated curve analysis associated CMV-pp65 CD4+ responses of > 0.03% in R(+)-patients with absence of concurrent (p = 0.003) and future CMV replication in the following 8 weeks (p = 0.036). GCV-resistant CMV replication occurred in 3 R(+)-patients (6.3%) with pp65- CD4+ frequencies < 0.03% (p = 0.041)., Conclusion: The data suggest that pp65-specific CD4+ T-cells might be useful to identify R(+)-patients at increased risk of CMV replication. Provided further corroborating evidence, CMV-pp65 CD4+ responses above 0.03% in PBMCs of KT patients under stable immunosuppression are associated with lower risk of concurrent and future CMV replication during the following 8 weeks.

Mutated p21 ras proteins (muRas) are present in approximately 90% of pancreatic adenocarcinomas and express mutants which can function as cancer-specific antigens. To evaluate the frequency and magnitude of the natural T-cell response against muRas in 19 HLA-A2-positive patients with muRas-positive pancreatic carcinomas, antigen-experienced T lymphocytes in fresh peripheral blood mononuclear cells were shown by IFN-gamma enzyme-linked immunospot using muRas peptides (5-21) that encompass both HLA class I (HLA-A2)- and class II-restricted (HLA-DRB1) epitopes. Six of 19 patients (32%) were found to have a specific T-cell response against individual mutation-specific ras(5-21) but not against other ras mutations or wild-type ras. In contrast, none of 19 healthy subjects had T cells specifically secreting IFN-gamma (P = 0.004). The T-cell response consisted of both CD8(+) and CD4(+) T cells but was dominated by CD8 T cells in three of four patients. MuRas(5-14) and muRas(6-14) were shown to specifically induce CD8(+) T-cell mediated cytotoxicity against HLA-A2-positive, muRas-bearing pancreatic carcinoma cells. The T-cell response was not correlated with prognostic or clinical variables such as tumor-node-metastasis status, stage, or survival. In conclusion, a natural T-cell response against muRas proteins that could be exploited for immunostimulatory therapeutic approaches has been shown in a significant proportion of patients with pancreatic cancer.

Several prevalent and life-threatening agents enter the organism via the mucosa. In this case, a mucosal cellular immune response is essential for protection and is therefore considered the main objective of vaccination. The frequency of antigen-specific CD4+ and CD8+ T cells can be determined directly in human whole blood by a combination of surface marker and intracellular cytokine staining. Immune cells primed in the mucosal compartment also migrate through the blood and can be identified by expression of the gut-specific homing receptor alpha4beta7. Simultaneously, these lymphocytes can be functionally characterized regarding their differentiation status by analysis of CD45RO and CD27 expression and effector functions by measuring intracellular perforin or granzyme B content. Thus, the technique described in the paper is a powerful tool for clinical monitoring of the total cellular immune response to complex antigens during infection or vaccination.

Background: In clinical practice, HLA matching is generally applied to minimize the incidence of graft rejection after transplantation. Recently, graft rejection has been directly associated with the presence of preformed alloreactive T cells before transplantation. Despite this knowledge, assays to rapidly quantify preformed alloreactivity are not available for use in a clinical setting. In this study, such an assay was developed and evaluated in a large cohort to correlate alloreactive T-cell reactivity with HLA matching., Methods: Stimulator peripheral blood mononuclear cells were prestained with CD45-fluorescein isothiocyanate antibody and mixed with responder peripheral blood mononuclear cells. Activation-induced cytokine secretion was blocked using brefeldin A. After 6 hr, functionally active alloreactive responder CD4 and CD8 T cells were quantified among fluorescein isothiocyanate-negative cells by their expression of interferon-gamma on flow cytometry., Results: Directly alloreactive CD4 and CD8 T cells among both stimulators and responders were easily distinguished after 6 hr of stimulation without being affected by bystander activation. Among 128 paired combinations, 23.4% of individuals had alloreactive CD8 T cells, 15.7% had alloreactive CD4 T cells, and 12.5% had alloreactivity in both T-cell subpopulations. Alloreactive T cells decreased from circulation within a few days after transplantation. In line with well-known clinical observations that associate HLA matching with graft outcome, the number of HLA-A and -B mismatches correlated with alloreactive CD8 T-cell frequencies in the whole study population, whereas it did not predict alloreactivity on an individual basis., Conclusion: Alloreactive T cells may rapidly be quantified after 6 hr of stimulation. Thus, the flow cytometric approach may be applied in a clinical setting to facilitate the individualization of immunosuppressive therapy and studies on the identification of patients who are at increased risk to develop graft rejection.

Infections with persistent viruses, such as cytomegalovirus (CMV) or adenovirus, are not, in general, clinically apparent but may cause serious complications in the immunocompromised host. As has been shown for CMV, the cellular arm of the immune response is essential in controlling viral replication. However, cellular immunity toward adenoviruses has not been well characterized in humans. The aim of the present study was the quantitative and functional analysis of adenovirus-specific T cell responses from 171 healthy individuals and 59 long-term renal transplant recipients by use of flow-cytometric, as well as standard proliferation and enzyme-linked immunosorbant, assays. Adenovirus-specific immunity is dominated by CD4 T cells with memory/effector phenotype. Of interest, the frequency of adenovirus-specific T cells decreases significantly with age. This age-related decline indicates the eventual elimination of adenoviruses within a lifetime that may explain the well-known clinical observation of a predominant incidence of adenoviral complications in children and young adults, compared with older adults, after transplantation.

Defective expression of B7-2 (CD86) on monocytes of dialysis patients correlates to the uremia-associated immune defect. Background. Specific cellular immune reactions in patients with chronic renal failure (CRF) are impaired by a defect of the antigen-presenting cells. To elucidate the molecular background for this defect, we determined the expression of human lymphocyte antigen (HLA)-DR and costimulatory molecules on monocytes of hemodialysis patients. Methods. The expression of HLA-DR, B7-1 (CD80), and B7-2 (CD86) molecules was determined on CD14+ monocytes of chronic hemodialysis patients prior to a dialysis session. Mononuclear cells of these patients were cultured, and expression of the respective antigens was determined after in vitro activation by various stimuli. Results were correlated with in vitro proliferation of T cells in a phytohemagglutinin (PHA) assay and the clinical response to a hepatitis B vaccination. All data were compared with healthy controls and patients with CRF who were not on dialysis. Results. Monocytes of chronic hemodialysis patients but not CRF patients expressed low levels of costimulatory B7-2, while HLA-DR expression was normal. B7-1 was only expressed on activated monocytes, and the expression reached normal levels in hemodialysis patients. Baseline expression of B7-2 highly correlated with the results of T-cell proliferation assays in hemodialysis patients and also with the clinical immune response. Conclusions. Impaired expression and up-regulation of B7-2 is an important feature of the cellular immune defect in chronic hemodialysis patients. It leads to reduced costimulation and effector activation of T cells and contributes to a molecular explanation for the impaired response of hemodialysis patients to the hepatitis B vaccination. [ABSTRACT FROM AUTHOR]