Blood dendritic cell levels associated with impaired IL‐12 production and T‐cell deficiency in patients with kidney disease: implications for post‐transplant viral infections

Reduced pretransplant blood myeloid dendritic cell (mDC) levels are associated with post‐transplant BK viremia and cytomegalovirus (CMV) disease after kidney transplantation. To elucidate potential mechanisms by which mDC levels might influence these outcomes, we studied the association of mDC levels with mDC IL‐12 production and T‐cell level/function. Peripheral blood (PB) was studied in three groups: (i) end stage renal disease patients on hemodialysis (HD; n = 81); (ii) chronic kidney disease stage IV‐V patients presenting for kidney transplant evaluation or the day of transplantation (Eval/Tx; n = 323); and (iii) healthy controls (HC; n = 22). Along with a statistically significant reduction in mDC levels, reduced CD8⁺ T‐cell levels were also demonstrated in the kidney disease groups compared with HC. Reduced PB mDC and monocyte‐derived DC (MoDC) IL‐12 production was observed after in vitro LPS stimulation in the HD versus HC groups. Finally, ELISpot assays demonstrated less robust CD3⁺ INF‐γ responses by MoDCs pulsed with CMV pp65 peptide from HD patients compared with HC. PB mDC level deficiency in patients with kidney disease is associated with deficient IL‐12 production and T‐cell level/function, which may explain the known correlation of CD8⁺ T‐cell lymphopenia with deficient post‐transplant antiviral responses.     

High‐Quality CMV‐Specific CD4+ Memory Is Enriched in the Lung Allograft and Is Associated With Mucosal Viral Control

The maintenance of CMV‐specific T cell memory in lung transplant recipients (LTRs) is critical for host defense and allograft durability, particularly in donor⁺/recipient^? (D⁺R^?) individuals who demonstrate increased mortality. We studied CD4⁺ and CD8⁺ CMV‐specific memory responses to phosphoprotein 65 (pp65) in a prospective cohort of 18 D⁺R^? LTRs, from bronchoalveolar lavage (BAL)‐obtained lung mononuclear cells (LMNC) and PBMC. Unexpectedly, pp65‐specific CD4⁺ and CD8⁺ IFN‐γ memory responses from LMNC were similar, in contrast to persistent CD8⁺ predominance in PBMC. Unlike the pulmonary CD8⁺ predominance during acute primary infection, compartmental equalization occurred in the CMV‐specific CD8⁺ memory pool during chronic infection, whereas CMV‐specific CD4⁺ memory was enriched in the bronchoalveolar space. Moreover, CMV‐specific CD4⁺ memory T cells with multifunctional production of IFN‐γ, TNF‐α, IL‐2 and MIP‐1β were significantly increased in LMNCs, in contrast to similar intercompartmental CD8⁺ memory function. Moreover, the absolute number of CMV‐specific CD4⁺IFN‐γ⁺ memory cells in BAL was significantly increased in LTRs exhibiting viral control compared to those with CMV early antigen positivity. Collectively, these data demonstrate both preferential distribution and functional quality of CMV‐specific CD4⁺ memory in the lung allograft during chronic infection, and show an important association with CMV mucosal immunity and viral control.     

Decreasing plasma soluble IL‐1 receptor antagonist and increasing monocyte activation early post‐transplant may be involved in pathogenesis of delayed graft function in renal transplant recipients

Sadeghi M, Daniel V, Naujokat C, Schmidt J, Mehrabi A, Zeier M, Opelz G. Decreasing plasma soluble IL‐1 receptor antagonist and increasing monocyte activation early post‐transplant may be involved in pathogenesis of delayed graft function in renal transplant recipients
Clin Transplant 2010: 24: 415–423. © 2009 John Wiley & Sons A/S. Abstract: Delayed graft function (DGF) increases the risk of acute allograft rejection and may affect long‐term graft survival. We compared pre‐transplant, early post‐transplant, and late post‐transplant serum creatinine (Cr) and plasma levels of neopterin, cytokines, and cytokine receptors/antagonists in patients with DGF (n = 39), slow graft function (SGF) (n = 43), or immediate graft function (IGF) (n = 30). Three and eight days post‐transplant, plasma neopterin (p < 0.001; p < 0.001), Soluble Interleukin‐6 (IL‐6) receptor (R) (p = 0.002; p = 0.001), and IL‐10 (p = 0.003; p = 0.001) were higher in DGF than IGF patients. One month post‐transplant, plasma neopterin (p < 0.001) and IL‐10 (p < 0.001) were higher in DGF than IGF patients. Three days post‐transplant, the results indicated reduced sIL‐1 receptor antognist (RA) production in DGF patients (p = 0.001). Simultaneously, plasma sIL‐6R and IL‐10 increased in DGF (p < 0.001; p = 0.003) and SGF (p = 0.007; p = 0.030) patients, indicating increased production of sIL‐6R and IL‐10. Lower sIL‐1 production in DGF than IGF patients early post‐transplant might promote the increased production of monocyte‐derived neopterin, sIL‐6R, and IL‐10. This monocyte/macrophage activation might induce inflammation in the graft and subsequently cause an impairment of graft function. Blocking of monocyte activity after renal transplantation may be considered a potential approach for improving graft outcome.     

Induction of porcine‐specific regulatory T cells with high specificity and expression of IL‐10 and TGF‐β1 using baboon‐derived tolerogenic dendritic cells

Background

Regulatory T cells (Treg) play an important role in maintenance of homeostasis in vivo. Treg application to alleviate allo‐organ rejection is being studied extensively. However, natural Treg (nTreg) expansion in vitro is laborious and expensive. Antigen‐specific Treg are more effective and require lower cell numbers than use of nTreg for immune control. The baboon, as a non‐human primate experimental animal model, is widely used in xenotransplantation research. An effective method to generate baboon xeno‐specific Treg would benefit research on immune tolerance in xenotransplantation using this model system.

Method

Baboon tolerogenic dendritic cells (tolDC) were generated in 3 days from monocytes isolated from baboon peripheral blood mononuclear cells in medium supplemented with anti‐inflammatory cytokines. After loading with porcine‐specific (PS) in vitro‐transcribed RNA (ivtRNA), tolDC were used to induce CD4⁺ T cells to become porcine‐specific Treg (PSTreg) in cocultures supplemented with IL‐2 and rapamycin for 10 days. Anti‐inflammatory and inflammatory cytokine expression was evaluated at the mRNA and protein levels in both baboon tolDC and PSTreg. Functional assays, suppression of activation markers on porcine‐specific effector T cells (PSTeff) and inhibition of PSTeff proliferation, were used to test PSTreg specificity.

Results

TolDC generated with this method exhibited a tolerogenic phenotype, expressed CCR7 and produced high levels of IL‐10 and TGF‐β1, whereas IL‐12p40 and IFN‐γ were not expressed. PSTreg were successfully generated in cocultures of CD4⁺ T cells and PS ivtRNA‐loaded tolDC. They exhibited a CD3⁺ CD4⁺ CD25⁺ CD127^low/? CD45RA^low Foxp3⁺ phenotype and were characterized by high expression of IL‐10 and TGF‐β1 mRNA and protein. They showed upregulated expression of EBI3 and GARP mRNA. PSTreg exhibited highly suppressive effects toward PSTeff, secreting high amounts of IL‐10 and TGF‐β1 cytokine upon interaction with PSTeff and suppressing IFN‐γ expression on PSTeff.

Conclusion

In this study, a fast 3‐day method to generate baboon‐derived tolDC is provided that allows subsequent induction of PSTreg displaying high porcine‐antigen specificity and expression of IL‐10 and TGF‐β1. Porcine‐specific baboon Treg can be used in porcine solid organ or cell xenotransplantation studies through adoptive cell transfer into host baboons.     

T helper 1, 2 and 17 cell subsets in renal transplant patients with delayed graft function

Ischemia‐reperfusion injury (IRI) in kidney transplantation is the major cause of delayed graft function (DGF), an event associated with an increased risk of acute rejection. The aim of this study was to evaluate T helper (Th) cell phenotype in renal transplants with DGF. T‐bet (Th1), GATA‐3 (Th2) and IL‐17 (Th17) protein expression was investigated in pretransplant biopsies, DGF and acute tubular damage (ATD) caused by calcineurin‐inhibitor toxicity. Intracytofluorimetric analysis of IFN‐γ, IL‐4 and IL‐17 was performed to analyze Th1, Th2 and Th17 responses in peripheral blood mononuclear cells of recipients with early graft function (EGF) and DGF, before (T0) and 24 h after transplantation (T24). In pretransplant biopsies, T‐bet⁺, GATA‐3⁺ and IL‐17⁺ cells were barely detectable. In DGF, T‐bet⁺ and IL‐17⁺ cells were significantly increased compared with pretransplant and ATD. More than 90% of T‐bet⁺ and less then 5% of IL‐17⁺ cells were CD4⁺. GATA‐3⁺ cells were increased to a lower extent. T‐bet⁺/GATA‐3⁺ cell ratio was significantly higher in DGF. Peripheral CD4⁺ IFN‐γ/IL‐4 ratio was significantly decreased in DGF, while CD4⁺/IL‐17⁺ cells did not differ between T0 and T24 in DGF. Our data suggest that DGF is characterized by a prevalent Th1 phenotype within the graft. This event might represent a link between DGF and acute rejection.     

The role of interleukin‐17 in murine cytomegalovirus interstitial pneumonia in mice with skin transplants

We hypothesized that the T helper (Th)17 response plays an important role in murine cytomegalovirus (MCMV) interstitial pneumonia. BALB/c mice with skin grafts from C57/BJ6 mice were intranasally inoculated with 1.0 × 10⁵ PFU MCMV. Lung tissues and skin grafts were histologically evaluated and expression of interleukins (IL)‐17, ‐6 and ‐8, monocyte chemotactic protein (MCP)‐1 and interferon (IFN)‐γ in serum and bronchoalveolar lavage (BAL) fluid, intracellular IL‐4, ‐17, and IFN‐γ, in spleen lymphocytes were analysed. The levels of IL‐17 in the serum and BAL fluid were significantly higher in MCMV‐infected mice versus not‐infected mice (P = 0.0286 and P = 0.007, respectively) and the BAL levels of IL‐17 peaked in 9 days (P = 0.001). The IL‐17 level in the BAL was correlated with the grade of lung interstitial inflammation (r = 0.554, P = 0.0144). Serum IFN‐γ levels were also higher after infection than that in the not‐infected mice (P = 0.0286). IL‐17 production increases locally and systemically during MCMV interstitial pneumonia. Neutralization of IL‐17 significantly suppressed lung inflammation at day14 as assessed by histology. These findings suggest that IL‐17 is important in the pathology of MCMV interstitial pneumonia.     

Functional analysis of CD4+ CD25bright T cells in kidney transplant patients: improving suppression of donor-directed responses after transplantation

Abstract: Background: The role of CD4⁺ CD25^bright regulatory T cells (Treg) in controlling alloreactivity is established, but little is known whether antigen‐specific Treg are induced in fully immunosuppressed kidney transplant patients. Methods: The frequency and function of CD25^bright T cells of nine stable kidney transplant patients before and 0.5–2 yr after transplantation were measured. Patients received triple therapy consisting of cyclosporine, mycophenolate mofetil and prednisone. To investigate the influence of transplantation and immunosuppression on Treg function, we compared their suppressive capacities pre‐ and post‐transplantation using mixed lymphocyte reactions and kept the CD25^?/dim effector T‐cell (Teff) population constant. Results: After transplantation, the percentage of CD4⁺ CD25^bright T cells significantly decreased from 8.5% pre‐transplant to 6.9% post‐transplant (median, p = 0.05). However, the lower percentage of post‐transplant CD4⁺ CD25^bright T cells was not associated with reduced, but rather improved suppressor function of these cells. The proliferative response of pre‐transplant Teff to donor‐antigens was more profoundly suppressed by post‐transplant Treg than by pre‐transplant Treg (pre‐transplant 18% vs. post‐transplant 55% median, p = 0.03) and was comparable against third party antigens at a CD25^bright:CD25^?/dim ratio of 1:20. Conclusions: In immunosuppressed kidney transplant patients, the donor‐directed suppressive capacity of CD4⁺ CD25^bright regulatory T cells improved, which may contribute to the development of donor‐specific hyporesponsiveness against the graft.     

Interferon‐γ plays a role in bone formation in vivo and rescues osteoporosis in ovariectomized mice

Interferon γ (IFN‐γ) is a cytokine produced locally in the bone microenvironment by cells of immune origin as well as mesenchymal stem cells. However, its role in normal bone remodeling is still poorly understood. In this study we first examined the consequences of IFN‐γ ablation in vivo in C57BL/6 mice expressing the IFN‐γ receptor knockout phenotype (IFNγR1^?/?). Compared with their wild‐type littermates (IFNγR1^+/+), IFNγR1^?/? mice exhibit a reduction in bone volume associated with significant changes in cortical and trabecular structural parameters characteristic of an osteoporotic phenotype. Bone histomorphometry of IFNγR1^?/? mice showed a low‐bone‐turnover pattern with a decrease in bone formation, a significant reduction in osteoblast and osteoclast numbers, and a reduction in circulating levels of bone‐formation and bone‐resorption markers. Furthermore, administration of IFN‐γ (2000 and 10,000 units) to wild‐type C57BL/6 sham‐operated (SHAM) and ovariectomized (OVX) female mice significantly improved bone mass and microarchitecture, mechanical properties of bone, and the ratio between bone formation and bone resorption in SHAM mice and rescued osteoporosis in OVX mice. These data therefore support an important physiologic role for IFN‐γ signaling as a potential new anabolic therapeutic target for osteoporosis. © 2011 American Society for Bone and Mineral Research.     

Cell line IDG‐SW3 replicates osteoblast‐to‐late‐osteocyte differentiation in vitro and accelerates bone formation in vivo

Osteocytes are the most abundant cells in bone yet are the most challenging to study because they are embedded in a mineralized matrix. We generated a clonal cell line called IDG‐SW3 (for Immortomouse/Dmp1‐GFP‐SW3) from long‐bone chips from mice carrying a Dmp1 promoter driving GFP crossed with the Immortomouse, which expresses a thermolabile SV40 large T antigen regulated by interferon γ (IFN‐γ). Cells from these mice can be expanded at 33 °C in the presence of IFN‐γ and then allowed to resume their original phenotype at 37 °C in the absence of IFN‐γ. IDG‐SW3 cells are Dmp1‐GFP^? and T antigen⁺ under immortalizing conditions but Dmp1‐GFP⁺ and T antigen^? under osteogenic conditions. Like osteoblasts, they express alkaline phosphatase and produce and mineralize a type 1 collagen matrix containing calcospherulites. Like early osteocytes, they express E11/gp38, Dmp1, MEPE, and Phex. Like late osteocytes, they develop a dendritic morphology and express SOST/sclerostin and fibroblast growth factor 23 (FGF‐23), regulated by parathyroid hormone (PTH) and 1,25‐dihydroxyvitamin D₃. When cultured on 3D matrices, they express Dmp1‐GFP and sclerostin. When the 3D cultures are implanted in calvarial defects in vivo, they accelerate bone healing. This cell line should prove useful for studying osteoblast‐to‐osteocyte transition, mechanisms for biomineralization, osteocyte function, and regulation of SOST/sclerostin and FGF‐23. © 2011 American Society for Bone and Mineral Research     

Role of Lentivirus‐Mediated Overexpression of Programmed Death‐Ligand 1 on Corneal Allograft Survival

To investigate the role of lentivirus‐mediated overexpression of programmed death‐ligand 1 (PD‐L1) on rat corneal allograft survival. A fully allogeneic rat cornea transplant model was used for in vivo studies. Lentiviral (LV) vectors are efficient tools for ex vivo genetic modification of cultured corneas. LV vector encoding for PD‐L1 (LV.PD‐L1) and LV vector encoding for eGFP (LV.eGFP, as control) were constructed and tested. PD‐L1 or eGFP expression was increased on corneal cells upon LV.PD‐L1 and LV.eGFP transduction, respectively. Both allogeneic controls and allogeneic LV.eGFP transduced corneas were uniformly rejected (MST: 13.8 ± 1.7 days and 12.3 ± 1.9 days, respectively). In contrast, allogeneic LV.PD‐L1 transduced corneas showed a high percentage (83%) of graft survival (MST > 30 days, n = 5, 15 days, n = 1). Graft opacity of PD‐L1 transduced corneas was present but was significantly reduced compared to control or eGFP expressing corneas. Flow cytometric analysis revealed that percentages of CD3⁺CD8⁺CD161⁺ and CD3⁺CD8⁺CD161^– lymphocytes were decreased in animals receiving LV.PD‐L1 transduced corneas compared to animals grafted with LV.eGFP transduced corneas. Moreover, reduced expression of proinflammatory cytokines (IFN‐γ and IL‐6) in PD‐L1 transduced corneas compared to allogeneic controls was also observed. Local PD‐L1 gene transfer in cultured corneas is a promising approach for the prolongation of corneal allograft survival and attenuation of graft rejection.     

Rapamycin‐Conditioned Donor Dendritic Cells Differentiate CD4+CD25+Foxp3+ T Cells In Vitro with TGF‐β1 for Islet Transplantation

Dendritic cells (DCs) conditioned with the mammalian target of rapamycin (mTOR) inhibitor rapamycin have been previously shown to expand naturally existing regulatory T cells (nTregs). This work addresses whether rapamycin‐conditioned donor DCs could effectively induce CD4⁺CD25⁺Foxp3⁺ Tregs (iTregs) in cell cultures with alloantigen specificities, and whether such in vitro‐differentiated CD4⁺CD25⁺Foxp3⁺ iTregs could effectively control acute rejection in allogeneic islet transplantation. We found that donor BALB/c bone marrow‐derived DCs (BMDCs) pharmacologically modified by the mTOR inhibitor rapamycin had significantly enhanced ability to induce CD4⁺CD25⁺Foxp3⁺ iTregs of recipient origin (C57BL/6 (B6)) in vitro under Treg driving conditions compared to unmodified BMDCs. These in vitro‐induced CD4⁺CD25⁺Foxp3⁺ iTregs exerted donor‐specific suppression in vitro, and prolonged allogeneic islet graft survival in vivo in RAG^?/‐ hosts upon coadoptive transfer with T‐effector cells. The CD4⁺CD25⁺Foxp3⁺ iTregs expanded and preferentially maintained Foxp3 expression in the graft draining lymph nodes. Finally, the CD4⁺CD25⁺Foxp3⁺ iTregs were further able to induce endogenous naïve T cells to convert to CD4⁺CD25⁺Foxp3⁺ T cells. We conclude that rapamycin‐conditioned donor BMDCs can be exploited for efficient in vitro differentiation of donor antigen‐specific CD4⁺CD25⁺Foxp3⁺ iTregs. Such in vitro‐generated donor‐specific CD4⁺CD25⁺Foxp3⁺ iTregs are able to effectively control allogeneic islet graft rejection.     

Foxp3+ T cells in peripheral blood of renal transplant recipients and clinical correlations

Aim: Immunophenotype peripheral blood T cells from renal transplant recipients (RTR) using cellular markers of regulatory T cells (Tregs) and flow cytometry, including Foxp3, and correlate these findings with clinical parameters. Methods: Expression of phenotypic markers of Tregs was assessed by flow cytometric analysis of peripheral blood lymphocytes (PBL) from (i) RTR (n = 95); (ii) patients with end‐stage renal failure (ESRF) awaiting transplantation (n = 17); and (iii) normal healthy controls (n = 18). Results: The percentage of CD4⁺CD25⁺Foxp3⁺ cells within the CD4⁺ cell population did not significantly alter at different time points post‐transplant. However, the percentage of CD4⁺CD25⁺Foxp3⁺ cells within the CD4⁺ population was significantly lower in RTR compared with patients with ESRF. In contrast, RTR and ESRF had a similar percentage of CD4⁺CD25⁺ cells expressing Foxp3. Multivariate analysis of PBL and clinical parameters demonstrated (i) a positive linear relationship between the percentage CD4⁺CD25⁺ cells expressing Foxp3 and estimated glomerular filtration rate and (ii) a higher percentage of CD4⁺CD25⁺ cells in the CD4⁺ cell population in patients with malignancy (the majority were skin cancers). Malignancy also correlated strongly with time post‐transplant and age of the RTR. Conclusion: Immune monitoring of the PBL phenotype in RTR using CD4, CD25 and Foxp3 may stratify RTR and predict graft outcome and function, and risk of complications from immunosuppression. Longitudinal and functional studies of Tregs are essential to extend the findings of the present study.     

De novo donor‐specific anti‐HLA antibodies after kidney transplantation are associated with impaired graft outcome independently of their C1q‐binding ability

Many aspects of post‐transplant monitoring of donor‐specific (DSA) and non‐donor‐specific (nDSA) anti‐HLA antibodies on renal allograft survival are still unclear. Differentiating them by their ability to bind C1q may offer a better risk assessment. We retrospectively investigated the clinical relevance of de novo C1q‐binding anti‐HLA antibodies on graft outcome in 611 renal transplant recipients. Acute rejection (AR), renal function, and graft survival were assessed within a mean follow‐up of 6.66 years. Post‐transplant 6.5% patients developed de novo DSA and 11.5% de novo nDSA. DSA (60.0%; P < 0.0001) but not nDSA (34.1%, P = 0.4788) increased rate of AR as compared with controls (27.4%). C1q‐binding anti‐HLA antibodies did not alter rate of AR in both groups. Renal function was only significantly diminished in patients with DSAC1q⁺. However, DSA significantly impaired 5‐year graft survival (65.2%; P < 0.0001) in comparison with nDSA (86.7%; P = 0.0054) and controls (90.7%). While graft survival did not differ between DSAC1q⁻ and DSAC1q⁺ recipients, 5‐year allograft survival was reduced in nDSAC1q⁺ (80.9%) versus nDSAC1q⁻ (90.7%, P = 0.0251). De novo DSA independently of their ability to bind C1q are associated with diminished graft survival.     

Adoptive transfer of FTY720‐treated immature BMDCs significantly prolonged cardiac allograft survival

A sphingosine 1 phosphate receptor modulator, FTY720, has been used to alleviate symptoms in allotransplantation and autoimmune disease models with impressive efficacy, while it only achieved moderate success in clinical trials. Infusion of immature bone marrow‐derived dendritic cell (BMDC) progenitors before transplantation could induce donor specific tolerance. In this study, we investigated the possibility of using FTY720‐DCs (FTY720‐treated immature BMDCs) to prevent severe alloimmune response. Our results indicate that FTY720‐DCs could markedly prolong graft survival compared with Ctrl‐DCs (nonconditioned immature BMDCs) as manifested by reduced inflammatory infiltration into the graft. IFN‐γ production by CD4⁺ and CD8⁺ T cells were significantly reduced, while FoxP3⁺ regulatory T cells among CD4⁺ T cells were upregulated. Although FTY720 seldom altered the phenotype or the phagocytosis of BMDCs in vitro, it severely hampered their capability to trigger antigen‐specific and allogeneic T‐cell response. When splenic T cells were co‐cultured with FTY720‐DCs, the proportion of regulatory T cells increased, accompanied by elevated IL‐10 production. Consistently, infusion of FTY720‐DCs could preferentially promote Treg proliferation and upregulate PD‐1 expression on conventional T cells in allogeneic mature BMDC priming experiment. These results suggest that infusion of FTY720‐DCs before cardiac transplantation could significantly prolong functional graft survival by acting as a balancer of alloimmune response.     

LFA‐1 Antagonism Inhibits Early Infiltration of Endogenous Memory CD8 T Cells into Cardiac Allografts and Donor‐Reactive T Cell Priming

Alloreactive memory T cells are present in virtually all transplant recipients due to prior sensitization or heterologous immunity and mediate injury undermining graft outcome. In mouse models, endogenous memory CD8 T cells infiltrate MHC‐mismatched cardiac allografts and produce IFN‐γ in response to donor class I MHC within 24 h posttransplant. The current studies analyzed the efficacy of anti‐LFA‐1 mAb to inhibit early CD8 T cell cardiac allograft infiltration and activation. Anti‐LFA‐1 mAb given to C57BL/6 6 (H‐2^b) recipients of A/J (H‐2^a) heart grafts on days –1 and 0 completely inhibited CD8 T cell allograft infiltration, markedly decreased neutrophil infiltration and significantly reduced intragraft expression levels of IFN‐γ‐induced genes. Donor‐specific T cells producing IFN‐γ were at low/undetectable numbers in spleens of anti‐LFA‐1 mAb treated recipients until day 21. These effects combined to promote substantial prolongation (from day 8 to 27) in allograft survival. Delaying anti‐LFA‐1 mAb treatment until days 3 and 4 posttransplant did not inhibit early memory CD8 T cell infiltration and proliferation within the allograft. These data indicate that peritransplant anti‐LFA‐1 mAb inhibits early donor‐reactive memory CD8 T cell allograft infiltration and inflammation suggesting an effective strategy to attenuate the negative effects of heterologous immunity in transplant recipients.     

Cyclosporine A Drives a Th17‐ and Th2‐Mediated Posttransplant Obliterative Airway Disease

Calcineurin‐inhibitor refractory bronchiolitis obliterans (BO) represents the leading cause of late graft failure after lung transplantation. T helper (Th)2 and Th17 lymphocytes have been associated with BO development. Taking advantage of a fully allogeneic trachea transplantation model in mice, we addressed the pathogenicity of Th cells in obliterative airway disease (OAD) occurring in cyclosporine A (CsA)‐treated recipients. We found that CsA prevented CD8⁺ T cell infiltration into the graft and downregulated the Th1 response but affected neither Th2 nor Th17 responses in vivo. In secondary mixed lymphocyte cultures, CsA dramatically decreased donor‐specific IFN‐γ production, enhanced IL‐17 production and did not affect IL‐13. As CD4⁺ depletion efficiently prevented OAD in CsA‐treated recipients, we further explored the role of Th2 and Th17 immunity in vivo. Although IL‐4 and IL‐17 deficient untreated mice developed an OAD comparable to wild‐type recipients, a single cytokine deficiency afforded significant protection in CsA‐treated recipients. In conclusion, CsA treatment unbalances T helper alloreactivity and favors Th2 and Th17 as coexisting pathways mediating chronic rejection of heterotopic tracheal allografts.     

Exogenous Interferon‐γ Immunotherapy for Invasive Fungal Infections in Kidney Transplant Patients

The incidence of invasive fungal infections (IFIs) in nonneutropenic solid organ transplant patients is increasing. We report our clinical experience with the use of interferon‐γ (IFN‐γ) immunotherapy in seven renal transplant patients who developed life threatening, disseminated IFIs refractory to conventional antifungal drug therapy. The infections were all microbiologically and histologically proven. The rapid cure of these disseminated infections with exogenous IFN‐γ injections was not associated with impaired kidney allograft function despite the use of liposomal amphotericin B in all cases. No clinical toxicity from the IFN‐γ immunotherapy was seen and no IFI relapsed during long‐term follow‐up. Our experience is both uncontrolled and in patients with unpredictable fungal infection‐related outcomes. However, compared to standard approaches, the accelerated cure of life threatening, disseminated IFIs with 6 weeks of combination antifungal drug therapy and IFN‐γ immunotherapy saved lives, retained allograft function and led to substantial cost savings in this small patient group.     

CMV‐specific T‐cell immunity,viral load,and clinical outcome in seropositive renal transplant recipients: a pilot study

Sund F, Lidehäll A‐K, Claesson K, Foss A, Tötterman TH, Korsgren O, Eriksson B‐M. CMV‐specific T‐cell immunity, viral load, and clinical outcome in seropositive renal transplant recipients: a pilot study.
Clin Transplant 2010: 24: 401–409. © 2009 Wiley Periodicals, Inc. Abstract: Background: Cytomegalovirus (CMV) infection is still the leading opportunistic infection following solid organ transplantation. The aim of this prospective study of renal transplant recipients was to evaluate the dynamics of CMV‐specific T‐cells, viral load, and clinical symptoms of CMV infection. Methods: Levels of tetramer‐selected CD8⁺ T‐cells (TetraCD8), CMV‐specific interferon‐γ producing CD8⁺ T‐cells (IFNγCD8), and CD4⁺ T‐cells (IFNγCD4), measured using major histocompatibility complex‐tetramer and cytokine flow cytometry techniques, and CMV DNA were monitored monthly in 17 CMV‐seropositive patients up to one yr (median 12 months, range 3–12) after transplantation and correlated to clinical outcome. Results: CMV DNAemia was detected in 94% of the patients, but only one patient developed CMV disease. CMV DNAemia >1 million copies/mL was seen in asymptomatic patients. CMV‐specific T‐cells decreased rapidly after transplantation. TetraCD8 and IFNγCD8 regenerated within three months, whereas IFNγCD4 recovery was impaired up to one yr after transplantation. The proportion of IFNγCD4 at two months post‐transplantation as compared with baseline, correlated strongly with the magnitude of the CMV DNAemia. Conclusions: Monitoring the reduction of IFNγCD4 compared with baseline during the first months after transplantation could be considered in predicting risk for high‐grade CMV DNAemia and in deciding strategic approaches for pre‐emptive and prophylactic therapy.     

Dynamic changes of B‐cell compartments in kidney transplantation: lack of transitional B cells is associated with allograft rejection

B cells play an important role in the immune responses which affect the outcomes of kidney allografts. Dynamic changes of B‐cell compartments in clinical kidney transplantation are still poorly understood. B‐cell subsets were prospectively monitored using flow cytometry for 1 year in 98 kidney transplant recipients. Data were correlated with immunosuppression and clinical outcomes. An increase in the total population of B lymphocytes was observed during the first week after transplantation. The level of IgM^highCD38^highCD24^high transitional B cells reduced significantly up until the third month, with partial repopulation in the first year. Lower numbers of transitional B cells in the third month were associated with higher risk of graft rejection. IgM⁺IgD⁺CD27^? naive B cells did not change within follow‐up. IgM⁺CD27⁺ nonswitched memory B cells and IgM^?CD27⁺ switched memory B cells increased on post‐operative day 7. IgM^?CD38^highCD27^high plasmablasts showed similar kinetics during the first post‐transplant year, similar to transitional B cells. In conclusion, sensitized kidney transplant recipients as well as those with either acute or chronic rejection within the first post‐transplant year exhibited lower levels of transitional B cells. Therefore, these data further support the hypothesis that transitional B cells have a protective role in kidney transplantation.