The Ratio of Circulating Regulatory T Cells (Tregs)/Th17 Cells Is Associated with Acute Allograft Rejection in Liver Transplantation

CD4⁺CD25⁺FoxP3⁺ regulatory T cells (Tregs) and Th17 cells are known to be involved in the alloreactive responses in organ transplantation, but little is known about the relationship between Tregs and Th17 cells in the context of liver alloresponse. Here, we investigated whether the circulating Tregs/Th17 ratio is associated with acute allograft rejection in liver transplantation. In present study, thirty-eight patients who received liver transplant were enrolled. The patients were divided into two groups: acute allograft rejection group (Gr-AR) (n = 16) and stable allograft liver function group (Gr-SF) (n = 22). The frequencies of circulating Tregs and circulating Th17 cells, as well as Tregs/Th17 ratio were determined using flow cytometry. The association between Tregs/Th17 ratio and acute allograft rejection was then analyzed. Our results showed that the frequency of circulating Tregs was significantly decreased, whereas the frequency of circulating Th17 cells was significantly increased in liver allograft recipients who developed acute rejection. Tregs/Th17 ratio had a negative correlation with liver damage indices and the score of rejection activity index (RAI) after liver transplantation. In addition, the percentages of CTLA-4⁺, HLA-DR⁺, Ki67⁺, and IL-10⁺ Tregs were higher in Gr-SF group than in Gr-AR group. Our results suggested that the ratio of circulating Tregs/Th17 cells is associated with acute allograft rejection, thus the ratio may serve as an alternative marker for the diagnosis of acute rejection.     

ICOS-Expressing Lymphocytes Promote Resolution of CD8-Mediated Lung Injury in a Mouse Model of Lung Rejection

Acute rejection, a common complication of lung transplantation, may promote obliterative bronchiolitis leading to graft failure in lung transplant recipients. During acute rejection episodes, CD8⁺ T cells can contribute to lung epithelial injury but the mechanisms promoting and controlling CD8-mediated injury in the lung are not well understood. To study the mechanisms regulating CD8⁺ T cell–mediated lung rejection, we used a transgenic model in which adoptively transferred ovalbumin (OVA)-specific cytotoxic T lymphocytes (CTL) induce lung injury in mice expressing an ovalbumin transgene in the small airway epithelium of the lungs (CC10-OVA mice). The lung pathology is similar to findings in humans with acute lung transplant. In the presence of an intact immune response the inflammation resolves by day 30. Using CC10-OVA.RAG^-/- mice, we found that CD4⁺ T cells and ICOS^+/+ T cells were required for protection against lethal lung injury, while neutrophil depletion was not protective. In addition, CD4⁺Foxp3 ⁺ ICOS⁺ T cells were enriched in the lungs of animals surviving lung injury and ICOS^+/+ Tregs promoted survival in animals that received ICOS^-/- T cells. Direct comparison of ICOS^-/- Tregs to ICOS^+/+ Tregs found defects in vitro but no differences in the ability of ICOS^-/- Tregs to protect from lethal lung injury. These data suggest that ICOS affects Treg development but is not necessarily required for Treg effector function.     

Thioredoxin Priming Prolongs Lung Allograft Survival by Promoting Immune Tolerance

Tolerance to allograft antigen is the major challenge and final goal of transplant medicine. Our previous study demonstrated that thioredoxin-1 (Trx) priming of donor lung significantly protected allogeneic lung graft. To determine whether Trx priming of donor lung inhibits allograft rejection, extends allograft survival and induces immune tolerance, orthotopic left lung transplantation was performed from Lewis to Sprague-Dawley rats without immunosuppression. Donor lungs were primed with Trx at 4°C for 4 hr prior to transplantation. After up to 37 days post-transplantation, allograft lung morphology, recipient T cell and humoral alloantigen-specific immune responses were examined. We found that Trx-primed lungs exhibited much reduced acute rejection and associated lung injuries resulting in loss of graft functional area at 5-37 days post-transplant in contrast to the control groups. CD4⁺ T cells from the recipients with Trx-primed grafts responded to the stimulation of dendritic cells (DCs) of donor origin, in contrast to DCs from the third party, with significantly reduced proliferation. Consistent with above findings, we observed that CD4⁺Foxp3⁺ regulatory T cells in spleen cells from the recipients with Trx-primed grafts were significantly increased compared to controls, and CD4⁺ T cells from the recipients with Trx-primed grafts produced much higher levels of immunosuppressive cytokine, IL-10 when stimulated with allogeneic donor DCs. In addition, humoral immune tolerance was also induced as there was no significant increase levels of serum antibodies against donor antigens in Trx-lung recipients when re-challenged with allogeneic donor antigens. Our results demonstrate that one-time Trx-priming of donor lung grafts prior to transplantation significantly prolongs the survival of the grafts through inducing or promoting cellular and humoral alloantigen-specific immune tolerance, which might be associated with the induction of immunosuppressive regulatory T cells.     

Total body irradiation of donors can alter the course of tolerance and induce acute rejection in a spontaneous tolerance rat liver transplantation model

Liver transplantation is an established therapy for end-stage liver diseases. Graft rejection occurs unless the recipient receives immunosuppression after transplantation. This study aimed to explore the mechanism of acute rejection of liver allografts in rats pre-treated with total body irradiation to eliminate passenger lymphocytes and to define the role of CD4⁺CD25⁺ regulatory T cells in the induction of immunotolerance in the recipient. Male Lewis rats were used as donors and male DA rats were recipients. Rats were randomly assigned to the following four groups: control group, homogeneity liver transplantation group, idio-immunotolerance group and acute rejection group. After transplantation, the survival time of each group, serum alanine aminotransferase, total bilirubin levels, number of Foxp3⁺CD4⁺CD25⁺ regulatory T cells, expression of glucocorticoid-induced tumor necrosis factor receptor on T cell subgroups, histopathology of the hepatic graft and spleen cytotoxic T lymphocyte lytic activity were measured. In the acute rejection group, where donors were preconditioned with total body irradiation before liver transplantation, all recipients died between day 17 and day 21. On day 14, serum alanine aminotransferase increased significantly to (459.2±76.9) U L^?1, total bilirubin increased to (124.1±33.7) ??mol L^?1 (P<0.05) and the ratio of Foxp3⁺CD4⁺CD25⁺ regulatory T cells decreased significantly to 1.50%±0.50% (P<0.05) compared with the other groups. Analysis of the T cell subpopulations in the acute rejection group varied from the other groups. Histological analysis showed typical changes of acute rejection in the acute rejection group only. Preconditioning of the donors with total body irradiation eliminated passenger lymphocytes of the liver graft, and thus affected the course of tolerance and induced acute rejection after liver transplantation.     

Increased expression of Tim-3 and its ligand Galectin-9 in rat allografts during acute rejection episodes

The aim of the study is to elucidate the profiles of T-cell immunoglobulin and mucin domain-3 (Tim-3) and its ligand Galecin-9 in acute pulmonary rejection by using a rat model of lung transplantation. Left lung grafts retrieved from Lewis or Fisher 344 rats were orthotopically transplanted into Lewis recipients without any immunosuppressions; the grafts were harvested at day 3, 7 or 10 after transplantation. The grade of acute rejection was histopathologically evaluated. Tim-3, Galectin-9, immune antigen and related cytokines expression were assessed with immunological techniques and real-time polymerase chain reaction (RT-PCR), respectively. Then, our results showed that Tim-3 and its ligand Galectin-9 were markedly up-regulated at protein and mRNA levels in allografts compared with syngrafts. Meanwhile, the decreased CD4/CD8 ratio was associated with acute rejection occurring and Tim-3 expression on CD4⁺ and CD8⁺ T cells in allografts was increased. Therefore, our study firstly described that enhanced Tim-3 and its ligand Galectin-9 in allografts might play an important role in the pathogenesis of rat lung transplant rejection, implying new valuable markers for detecting acute allograft rejection.     

Balance of Th1 and Th17 effector and peripheral regulatory T cells

Transfer of antigen-specific T cells into antigen-expressing lymphopenic recipients leads to the sequential generation of Th1 and Th17 effector and protective CD25⁺FoxP3⁺ regulatory cells in the periphery with surprisingly different kinetics. Such an experimental model is potentially valuable for defining the stimuli that regulate lineage decision and plasticity of various T cell effectors and peripheral regulatory T cells. Our studies have shown that IL-17 production occurs rapidly and declines within the first week with the appearance of IFN-γ producing T cells. Regulatory T cells appear during the recovery phase of the disease. The factors that mediate this complex differentiation originating from a starting naïve T cell population remain to be defined.     

Th1 to Th2 immune deviation facilitates,but does not cause,islet allograft tolerance in mice

It has been reported that Th1 to Th2 immune deviation effectively promotes peripheral tolerance in situations involving a limited T cell clone size, such as T cell-dependent autoimmunity and transplantation across minor, but not major, histocompatibility barriers. In this study, we tested the hypothesis that while Th1 to Th2 immune deviation fails to induce tolerance in the MHC-mismatched islet allograft model, it may promote a state that is permissive for tolerance induction. Here, we report that anti-IL-12 did not prevent acute rejection of islet allografts when administered alone. In conjunction with CTLA4/Fc, however, anti-IL-12 greatly facilitated long-term engraftment in three MHC-mismatched strain combinations. Similarly, while non-cytolytic IL-4/Fc, a long-lasting form of IL-4, did not prevent acute graft rejection when administered alone, a low, but not a high, dose of IL-4/Fc synergized with CTLA4/Fc in inducing significant levels of islet allograft tolerance. Moreover, by using a skin allograft adoptive transfer model, we show that these effects induced by anti-IL-12 and IL-4/Fc treatment were associated with an enhancement of the suppressive properties of CD4⁺CD25⁺ regulatory T cells. Thus, anti-IL-12 and low-dose IL-4/Fc facilitate, but do not cause, islet allograft tolerance in mice by increasing the immunosuppressive potency of CD4⁺CD25⁺ regulatory T cells.     

TIM-3: a novel regulatory molecule of alloimmune activation

T cell Ig domain and mucin domain (TIM)-3 has previously been established as a central regulator of Th1 responses and immune tolerance. In this study, we examined its functions in allograft rejection in a murine model of vascularized cardiac transplantation. TIM-3 was constitutively expressed on dendritic cells and natural regulatory T cells (Tregs) but only detected on CD4(+)FoxP3(-) and CD8(+) T cells in acutely rejecting graft recipients. A blocking anti-TIM-3 mAb accelerated allograft rejection only in the presence of host CD4(+) T cells. Accelerated rejection was accompanied by increased frequencies of alloreactive IFN-γ-, IL-6-, and IL-17-producing splenocytes, enhanced CD8(+) cytotoxicity against alloantigen, increased alloantibody production, and a decline in peripheral and intragraft Treg/effector T cell ratio. Enhanced IL-6 production by CD4(+) T cells after TIM-3 blockade plays a central role in acceleration of rejection. Using an established alloreactivity TCR transgenic model, blockade of TIM-3 increased allospecific effector T cells, enhanced Th1 and Th17 polarization, and resulted in a decreased frequency of overall number of allospecific Tregs. The latter is due to inhibition in induction of adaptive Tregs rather than prevention of expansion of allospecific natural Tregs. In vitro, targeting TIM-3 did not inhibit nTreg-mediated suppression of Th1 alloreactive cells but increased IL-17 production by effector T cells. In summary, TIM-3 is a key regulatory molecule of alloimmunity through its ability to broadly modulate CD4(+) T cell differentiation, thus recalibrating the effector and regulatory arms of the alloimmune response.     

The Presence of HLA-E-Restricted,CMV-Specific CD8+ T Cells in the Blood of Lung Transplant Recipients Correlates with Chronic Allograft Rejection

The human cytomegalovirus (CMV) immune evasion protein, UL40, shares an identical peptide sequence with that found in the leader sequence of many human leukocyte antigen (HLA)-C alleles and when complexed with HLA-E, can modulate NK cell functions via interactions with the CD94-NKG2 receptors. However the UL40-derived sequence can also be immunogenic, eliciting robust CD8+ T cell responses. In the setting of solid organ transplantation these T cells may not only be involved in antiviral immunity but also can potentially contribute to allograft rejection when the UL40 epitope is also present in allograft-encoded HLA. Here we assessed 15 bilateral lung transplant recipients for the presence of HLA-E-restricted UL40 specific T cells by tetramer staining of peripheral blood mononuclear cells (PBMC). UL40-specific T cells were observed in 7 patients post-transplant however the magnitude of the response varied significantly between patients. Moreover, unlike healthy CMV seropositive individuals, longitudinal analyses revealed that proportions of such T cells fluctuated markedly. Nine patients experienced low-grade acute cellular rejection, of which 6 also demonstrated UL40-specific T cells. Furthermore, the presence of UL40-specific CD8⁺ T cells in the blood was significantly associated with allograft dysfunction, which manifested as Bronchiolitis Obliterans Syndrome (BOS). Therefore, this study suggests that minor histocompatibility antigens presented by HLA-E can represent an additional risk factor following lung transplantation.     

Longitudinal Analysis of T and B Cell Phenotype and Function in Renal Transplant Recipients with or without Rituximab Induction Therapy

Background

Prevention of rejection after renal transplantation requires treatment with immunosuppressive drugs. Data on their in vivo effects on T- and B-cell phenotype and function are limited.

Methods

In a randomized double-blind placebo-controlled study to prevent renal allograft rejection, patients were treated with tacrolimus, mycophenolate mofetil (MMF), steroids, and a single dose of rituximab or placebo during transplant surgery. In a subset of patients, we analyzed the number and phenotype of peripheral T and B cells by multiparameter flow cytometry before transplantation, and at 3, 6, 12, and 24 months after transplantation.

Results

In patients treated with tacrolimus/MMF/steroids the proportion of central memory CD4⁺ and CD8⁺ T cells was higher at 3 months post-transplant compared to pre-transplant levels. In addition, the ratio between the percentage of central memory CD4⁺ and CD4⁺ regulatory T cells was significantly higher up to 24 months post-transplant compared to pre-transplant levels. Interestingly, treatment with tacrolimus/MMF/steroids resulted in a shift toward a more memory-like B-cell phenotype post-transplant. Addition of a single dose of rituximab resulted in a long-lasting B-cell depletion. At 12 months post-transplant, the small fraction of repopulated B cells consisted of a high percentage of transitional B cells. Rituximab treatment had no effect on the T-cell phenotype and function post-transplant.

Conclusions

Renal transplant recipients treated with tacrolimus/MMF/steroids show an altered memory T and B-cell compartment post-transplant. Additional B-cell depletion by rituximab leads to a relative increase of transitional and memory-like B cells, without affecting T-cell phenotype and function.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00565331","term_id":"NCT00565331"}}NCT00565331     

Loss of CD28 on Peripheral T Cells Decreases the Risk for Early Acute Rejection after Kidney Transplantation

Background

End-stage renal disease patients have a dysfunctional, prematurely aged peripheral T-cell system. Here we hypothesized that the degree of premature T-cell ageing before kidney transplantation predicts the risk for early acute allograft rejection (EAR).

Methods

222 living donor kidney transplant recipients were prospectively analyzed. EAR was defined as biopsy proven acute allograft rejection within 3 months after kidney transplantation. The differentiation status of circulating T cells, the relative telomere length and the number of CD31⁺ naive T cells were determined as T-cell ageing parameters.

Results

Of the 222 patients analyzed, 30 (14%) developed an EAR. The donor age and the historical panel reactive antibody score were significantly higher (p = 0.024 and p = 0.039 respectively) and the number of related donor kidney transplantation was significantly lower (p = 0.018) in the EAR group. EAR-patients showed lower CD4⁺CD28null T-cell numbers (p<0.01) and the same trend was observed for CD8⁺CD28null T-cell numbers (p = 0.08). No differences regarding the other ageing parameters were found. A multivariate Cox regression analysis showed that higher CD4⁺CD28null T-cell numbers was associated with a lower risk for EAR (HR: 0.65, p = 0.028). In vitro, a significant lower percentage of alloreactive T cells was observed within CD28null T cells (p<0.001).

Conclusion

Immunological ageing-related expansion of highly differentiated CD28null T cells is associated with a lower risk for EAR.     

Age related changes in T cell mediated immune response and effector memory to Respiratory Syncytial Virus (RSV) in healthy subjects

Respiratory syncytial virus (RSV) is the major pathogen causing respiratory disease in young infants and it is an important cause of serious illness in the elderly since the infection provides limited immune protection against reinfection. In order to explain this phenomenon, we investigated whether healthy adults of different age (20-40; 41-60 and > 60 years), have differences in central and effector memory, RSV-specific CD8+ T cell memory immune response and regulatory T cell expression status. In the peripheral blood of these donors, we were unable to detect any age related difference in term of central (CD45RA^-CCR7⁺) and effector (CD45RA^-CCR7^-) memory T cell frequency. On the contrary, we found a significant increase in immunosuppressive regulatory (CD4⁺25⁺FoxP3⁺) T cells (T_reg) in the elderly. An immunocytofluorimetric RSV pentamer analysis performed on these donors' peripheral blood mononuclear cells (PBMCs), in vitro sensitized against RSV antigen, revealed a marked decline in long-lasting RSV specific CD8+ memory T cell precursors expressing interleukin 7 receptor α (IL-7Rα), in the elderly. This effect was paralleled by a progressive switch from a Th1 (IFN-γ and TNF-α) to a Th2 (IL-10) functional phenotype. On the contrary, an increase in T_reg was observed with aging. The finding of T_reg over-expression status, a prominent Th2 response and an inefficient RSV-specific effector memory CD8+ T cell expansion in older donors could explain the poor protection against RSV reinfection and the increased risk to develop an RSV-related severe illness in this population. Our finding also lays the basis for new therapeutic perspectives that could limit or prevent severe RSV infection in elderly.     

CD160Ig Fusion Protein Targets a Novel Costimulatory Pathway and Prolongs Allograft Survival

CD160 is a cell surface molecule expressed by most NK cells and approximately 50% of CD8⁺ cytotoxic T lymphocytes. Engagement of CD160 by MHC class-I directly triggers a costimulatory signal to TCR-induced proliferation, cytokine production and cytotoxic effector functions. The role of CD160 in alloimmunity is unknown. Using a newly generated CD160 fusion protein (CD160Ig) we examined the role of the novel costimulatory molecule CD160 in mediating CD4⁺ or CD8⁺ T cell driven allograft rejection. CD160Ig inhibits alloreactive CD8⁺ T cell proliferation and IFN-γ production in vitro, in particular in the absence of CD28 costimulation. Consequently CD160Ig prolongs fully mismatched cardiac allograft survival in CD4^−/−, CD28^−/− knockout and CTLA4Ig treated WT recipients, but not in WT or CD8^−/− knockout recipients. The prolonged cardiac allograft survival is associated with reduced alloreactive CD8⁺ T cell proliferation, effector/memory responses and alloreactive IFN-γ production. Thus, CD160 signaling is particularly important in CD28-independent effector/memory CD8⁺ alloreactive T cell activation in vivo and therefore may serve as a novel target for prevention of allograft rejection.     

CXCR3 in T cell function

CXCR3 is a chemokine receptor that is highly expressed on effector T cells and plays an important role in T cell trafficking and function. CXCR3 is rapidly induced on naïve cells following activation and preferentially remains highly expressed on Th1-type CD4⁺ T cells and effector CD8⁺ T cells. CXCR3 is activated by three interferon-inducible ligands CXCL9 (MIG), CXCL10 (IP-10) and CXCL11 (I-TAC). Early studies demonstrated a role for CXCR3 in the trafficking of Th1 and CD8 T cells to peripheral sites of Th1-type inflammation and the establishment of a Th1 amplification loop mediated by IFNγ and the IFNγ-inducible CXCR3 ligands. More recent studies have also suggested that CXCR3 plays a role in the migration of T cells in the microenvironment of the peripheral tissue and lymphoid compartment, facilitating the interaction of T cells with antigen presenting cells leading to the generation of effector and memory cells.     

A tolerogenic semimature dendritic cells induce effector T-cell hyporesponsiveness by activation of antigen-specific CD4+CD25+ T regulatory cells that promotes skin allograft survival in mice

Semimature dendritic cells (smDCs) can induce autoimmune tolerance by activation of host antigen-specific CD4⁺CD25⁺ regulatory T (Treg) cells. We hypothesized that donor smDCs injected into recipients would induce effector T-cell hyporesponsiveness by activating CD4⁺CD25⁺Treg cells, and promote skin allograft survival. Myeloid smDCs were derived from C57BL/6J mice (donors) in vitro. BALB/c mice (recipients) were injected with smDCs to generate antigen-specific CD4⁺CD25⁺Treg cells in vivo. Allograft survival was prolonged when BALB/c recipients received either C57BL/6J smDCs prior to grafting or C57BL/6J smDC-derived CD4⁺CD25⁺Treg cells post-grafting, and skin flaps from these grafts showed the highest IL-10 production regardless of rapamycin treatments. Our findings confirm that smDCs constitute an independent subgroup of DCs that play a key role for inducing CD4⁺CD25⁺Treg cells to express high IL-10 levels, which induce hyporesponsiveness of effector T cells. Pre-treating recipients with donor smDCs may have potential for transplant tolerance induction.     

Peripheral CD4CD8 cells are the activated T cells expressed granzyme B (GrB), Foxp3, interleukin 17 (IL-17), at higher levels in Th1/Th2 cytokines

Peripheral CD4⁺CD8⁺ T cells have been identified as a T cell subset existing in animals and humans. However, the characterization of CD4⁺CD8⁺ T cells, their relationship with T memory (T_M), T effector (T_E), Th1/Th2, Treg and Th-17, remain unclear. This study was to characterize the CD4⁺CD8⁺ T cells. The results from human subjects showed that activated T cells were CD4⁺CD8⁺ T cells, comprised CD4^hiCD8^lo, CD4^hiCD8^hi and CD4^loCD8^hi subsets. They expressed CD62L^hi/lo, granzyme B (GrB), CD25, Foxp3, interleukin 17 (IL-17) and the cytokines of both Th1 and Th2, and had cytolytic function. These findings suggested that CD4⁺CD8⁺ T cells had over-lap function while they kept diversity, and that T cells could be divided into two major populations: activated and inactivated. Hence, the hypotheses of Th1/Th2, Treg and Th-17 might reflect the positive/negative feedback regulation of immune system. When compared to GrB⁺CD62L^lo T effector (T_E) cells, GrB⁺CD62L^hi T central memory effector (T_CME) cells had a quicker response to virus without CD62L loss.     

Vaccination with Embryonic Stem Cells Protects against Lung Cancer: Is a Broad-Spectrum Prophylactic Vaccine against Cancer Possible?

The antigenic similarity between tumors and embryos has been appreciated for many years and reflects the expression of embryonic gene products by cancer cells and/or cancer-initiating stem cells. Taking advantage of this similarity, we have tested a prophylactic lung cancer vaccine composed of allogeneic murine embryonic stem cells (ESC). Naïve C57BL/6 mice were vaccinated with ESC along with a source of granulocyte macrophage-colony stimulating factor (GM-CSF) in order to provide immunostimulatory adjuvant activity. Vaccinated mice were protected against subsequent challenge with implantable Lewis lung carcinoma (LLC). ESC-induced anti-tumor immunity was not due to a non-specific “allo-response” as vaccination with allogeneic murine embryonic fibroblasts did not protect against tumor outgrowth. Vaccine efficacy was associated with robust tumor-reactive primary and memory CD8⁺ T effector responses, Th1 cytokine response, higher intratumoral CD8⁺ T effector/CD4⁺CD25⁺Foxp3⁺ T regulatory cell ratio, and reduced myeloid derived suppressor cells in the spleen. Prevention of tumorigenesis was found to require a CD8-mediated cytotoxic T lymphocyte (CTL) response because in vivo depletion of CD8⁺ T lymphocytes completely abrogated the protective effect of vaccination. Importantly, this vaccination strategy also suppressed the development of lung cancer induced by the combination of carcinogen administration and chronic pulmonary inflammation. Further refinement of this novel vaccine strategy and identification of shared ESC/tumor antigens may lead to immunotherapeutic options for lung cancer patients and, perhaps more importantly, could represent a first step toward the development of prophylactic cancer vaccines.     

Association of Soluble HLA-G with Acute Rejection Episodes and Early Development of Bronchiolitis Obliterans in Lung Transplantation

Lung transplantation has evolved into a life-saving therapy for select patients with end-stage lung diseases. However, long-term survival remains limited because of bronchiolitis obliterans syndrome (BOS). Soluble HLA-G, a mediator of adaptive immunity that modulates regulatory T cells and certain classes of effector T cells, may be a useful marker of survival free of BOS. We conducted a retrospective, single-center, pilot review of 38 lung transplant recipients who underwent collection of serum and bronchoalveolar lavage fluid 3, 6 and 12 months after transplantation, and compared soluble HLA-G concentrations in each to the presence of type A rejection and lymphocytic bronchiolitis in the first 12 months and to the presence of BOS at 24 months after transplantation. Lung soluble HLA-G concentrations were directly related to the presence of type A rejection but not to lymphocytic bronchiolitis. Our data demonstrate that soluble HLA-G concentrations in bronchoalveolar lavage but not in serum correlates with the number of acute rejection episodes in the first 12 months after lung transplantation, and thus may be a reactive marker of rejection.     

Immunological monitoring of renal transplant recipients to predict acute allograft rejection following the discontinuation of tacrolimus

Background

Transplant patients would benefit from reduction of immunosuppression providing that graft rejection is prevented. We have evaluated a number of immunological markers in blood of patients in whom tacrolimus was withdrawn after renal transplantation. The alloreactive precursor frequency of CD4+ and CD8+ T cells, the frequency of T cell subsets and the functional capacity of CD4+CD25+FoxP3+ regulatory T cells (Treg) were analyzed before transplantation and before tacrolimus reduction. In a case-control design, the results were compared between patients with (n = 15) and without (n = 28) acute rejection after tacrolimus withdrawal.

Principal Findings

Prior to tacrolimus reduction, the ratio between memory CD8+ T cells and Treg was higher in rejectors compared to non-rejectors. Rejectors also had a higher ratio between memory CD4+ T cells and Treg, and ratios <20 were only observed in non-rejectors. Between the time of transplantation and the start of tacrolimus withdrawal, an increase in naive T cell frequencies and a reciprocal decrease of effector T cell percentages was observed in rejectors. The proportion of Treg within the CD4+ T cells decreased after transplantation, but anti-donor regulatory capacity of Treg remained unaltered in rejectors and non-rejectors.

Conclusions

Immunological monitoring revealed an association between acute rejection following the withdrawal of tacrolimus and 1) the ratio of memory T cells and Treg prior to the start of tacrolimus reduction, and 2) changes in the distribution of naive, effector and memory T cells over time. Combination of these two biomarkers allowed highly specific identification of patients in whom immunosuppression could be safely reduced.     

Polymorphisms in the cytotoxic T-lymphocyte antigen 4 gene and acute rejection risk in transplant recipients

Cytotoxic T-lymphocyte antigen 4 (CTLA-4) gene polymorphisms have been reported to influence the risk for acute rejection (AR) in transplant recipients. However, the results still remain controversial and ambiguous. The objective of the current study was to conduct a meta-analysis investigating the association between polymorphisms in the CTLA-4 gene and the risk of AR in transplant recipients. Electronic searches for all publications were conducted on associations between this variant and acute rejection in Medline and Embase databases through November 2011. Crude odds ratios (ORs) with 95 % confidence intervals (CIs) were calculated to estimate the strength of the association. Three polymorphisms (+49 adenine/guanine [+49A/G], -318 cytosine/thymine [-318C/T], and the +6230G/A polymorphism [CT60]) in 18 case-control studies from ten articles were analyzed. This meta-analysis included 2,081 cases of transplant recipients in which 813 cases developed AR and 1,268 cases did not develop AR. The results indicated that there was no statistically significant association between the risk of AR and the +49A/G polymorphism or the -318C/T polymorphism (+49A/G: OR = 0.876, 95 % CI = 0.650-1.180 for GG vs. AA; OR = 1.121, 95 % CI = 0.911-1.379 for AG + GG vs. AA; -318C/T: OR = 0.397, 95 % CI = 0.138-1.143 for TT vs. CC; OR = 0.987, 95 %CI = 0.553-1.760 for CT + TT vs. CC). However, individuals who carried CT60 A allele might have a decreased risk of AR (AA vs. GG OR = 0.535, 95 % CI = 0.340-0.841, A vs. G OR = 0.759, 95 % CI = 0.612-0.914) in liver transplant recipients among Europeans, but because only two studies were included, so the result should be caution. In further stratified analyses for the +49A/G and the -318C/T polymorphisms, no obvious significant associations were found in subgroups of renal transplant recipients and Europeans, a reduced incidence of acute rejection was observed in liver transplant recipients that are homogenous for +49G (OR = 0.638, 95 % CI = 0.427-0.954 for GG vs. AA/AG), while this has not been observed in renal transplant recipients. Overall this meta-analysis suggests that +49A/G and the -318C/T polymorphisms in CTLA-4 may be not associated with the risk of rejection after organ transplantation, but CTLA +49A/G and +6230G/A polymorphisms may be associated with acute rejection after liver transplantation, not after renal transplantation. In future, more studies should be included to evaluate the association between +6230G/A polymorphism and AR risk.