CD4 T Cells but Not Th17 Cells Are Required for Mouse Lung Transplant Obliterative Bronchiolitis

Lung transplant survival is limited by obliterative bronchiolitis (OB), but the mechanisms of OB development are unknown. Previous studies in a mouse model of orthotopic lung transplantation suggested a requirement for IL‐17. We have used this orthotopic mouse model to investigate the source of IL‐17A and the requirement for T cells producing IL‐17A. The major sources of IL‐17A were CD4⁺ T cells and γδ T cells. Depletion of CD4⁺ T cells led to a significantly decreased frequency and number of IL‐17A⁺ lymphocytes and was sufficient to prevent acute rejection and OB. However, mice with STAT3‐deficient T cells, which are unable to differentiate into Th17 cells, rejected lung allografts and developed OB similar to control mice. The frequency of IL‐17A⁺ cells was not decreased in mice with STAT3‐deficient T cells due mainly to the presence of IL‐17A⁺ γδ T cells. Deficiency of γδ T cells also did not affect the development of airway fibrosis. Our data suggest that CD4⁺ T cells are required for OB development and expansion of IL‐17A responses in the lung, while Th17 and γδ T cells are not absolutely required and may compensate for each other.     

Assessing Antibody Strength: Comparison of MFI,C1q,and Titer Information

The presence of donor‐specific HLA antibodies before or after transplantation may have different implications based on the antibody strength. Yet, current approaches do not provide information regarding the true antibody strength as defined by antigen–antibody dissociation rate. To assess currently available methods, we compared between neat mean fluorescence intensity (MFI) values, C1q MFI values, ethylenediaminetetraacetic acid (EDTA)‐treated samples, as well as titration studies and peak MFI values of over 7000 Luminex‐based single‐antigen HLA antibody data points. Our results indicate that neat MFI values do not always accurately depict antibody strength. We further showed that EDTA treatment (6%) does not always remove all inhibitory factors compared with C1q or titration studies. In this study of patients presenting with multiple antibody specificities, a prozone effect was observed in 71% of the cohort (usually not affecting all antibody specificities within a single serum sample, though). Similar to titration studies, the C1q assay was able to address the issue of potential inhibition; however, its limitation is its low sensitivity and inability to detect the presence of weak antibodies. Titration studies are the only method among the approaches used in this study to provide information suggesting antigen–antibody dissociation rates and are, therefore, likely to provide better indication of true antibody strength.     

Th‐17 Alloimmune Responses in Renal Allograft Biopsies From Recipients of Kidney Transplants Using Extended Criteria Donors During Acute T Cell–Mediated Rejection

Although renal transplantation using expanded criteria donors has become a common practice, immune responses related to immunosenescence in those kidney allografts have not been studied yet in humans. We performed a retrospective molecular analysis of the T cell immune response in 43 kidney biopsies from patients with acute T cell–mediated rejection including 25 from recipients engrafted with a kidney from expanded criteria donor and 18 from recipients grafted with optimal kidney allograft. The clinical, transplant and acute T cell–mediated rejection characteristics of both groups were similar at baseline. The expression of RORγt, Il‐17 and T‐bet mRNA was significantly higher in the elderly than in the optimal group (p = 0.02, p = 0.036, and p = 0.01, respectively). Foxp3 mRNA levels were significantly higher in elderly patients experiencing successful acute T cell–mediated rejection reversal (p = 0.03). The presence of IL‐17 mRNA was strongly associated with nonsuccessful reversal in elderly patients (p = 0.008). Patients with mRNA IL17 expression detection and low mRNA Foxp3 expression experienced significantly more treatment failure (87.5%) than patients with no mRNA IL17 expression and/or high mRNA Foxp3 expression (26.7%; p = 0.017). Our study suggests that the Th17 pathway is involved in pathogenesis and prognosis of acute T cell–mediated rejection in recipients of expanded criteria allograft.     

Transplanting Kidneys from Deceased Donors With Severe Acute Kidney Injury

Our aim was to determine outcomes with transplanting kidneys from deceased donors with acute kidney injury, defined as a donor with terminal serum creatinine ≥2.0 mg/dL, or a donor requiring acute renal replacement therapy. We included all patients who received deceased donor kidney transplant from June 2004 to October 2013. There were 162 AKI donor transplant recipients (21% of deceased donor transplants): 139 in the standard criteria donor (SCD) and 23 in the expanded criteria donor (ECD) cohort. 71% of the AKI donors had stage 3 (severe AKI), based on acute kidney injury network (AKIN) staging. Protocol biopsies were done at 1, 4, and 12 months posttransplant. One and four month formalin‐fixed paraffin embedded (FFPE) biopsies from 48 patients (24 AKI donors, 24 non‐AKI) underwent global gene expression profiling using DNA microarrays (96 arrays). DGF was more common in the AKI group but eGFR, graft survival at 1 year and proportion with IF/TA>2 at 1 year were similar for the two groups. At 1 month, there were 898 differentially expressed genes in the AKI group (p‐value <0.005; FDR <10%), but by 4 months there were no differences. Transplanting selected kidneys from deceased donors with AKI is safe and has excellent outcomes.     

Comparing Humoral and Cellular Immune Response Against HBV Vaccine in Kidney Transplant Patients

Host protection upon vaccination usually results from the complex interplay of humoral and cellular components of the immune system. Exploring hepatitis B surface antigen (HBsAg)‐specific T cell responses and their correlation with humoral responses under immunosuppression, we analyzed 51 renal transplant recipients, differing in HBV vaccine–specific antibody titers (non [NRs]‐, low [LRs]‐, and high responders [HRs]) and in 22 healthy controls (HCs) in a cross‐sectional study. HBsAg‐specific T cells were analyzed by flow cytometry according to expression of activation markers CD40L and/or CD69, and the cytokines IFNγ, IL‐2, TNFα, and IL‐17. No significant differences in responder rate and magnitude of HBsAg‐specific T cell responses were found between HCs and HRs. Interestingly, HBsAg‐specific Th‐cells were also observed in 50% of humoral NRs. Frequencies of HBsAg‐specific CD40L+ Th‐cells were significantly higher in HRs compared to LRs (p = 0.009) and in LRs in comparison to NRs (p = 0.043). All but NRs showed a predominance of multi‐potent HBsAg‐specific TNFα+IL‐2+ Th‐cells. As expected, HBsAg‐specific CD8⁺ T cells were rarely found. In conclusion, mounting of hepatitis B vaccine‐specific T cell responses is possible in kidney transplant recipients despite immunosuppression. Detection of HBV‐specific Th‐cells in a significant proportion of humoral NRs contributes to the current discussion on conferring immune protection by cellular memory in such patients.     

MicroRNA‐494 Promotes Cyclosporine‐Induced Nephrotoxicity and Epithelial to Mesenchymal Transition by Inhibiting PTEN

A major complication associated with cyclosporine (CsA) treatment is nephrotoxicity. In this study, we examined whether microRNAs play a role in cyclosporine‐induced nephrotoxicity. Treatment of mice with CsA resulted in nephrotoxicity that was associated with an early increase in expression of microRNA mmu‐miR‐494 (miR‐494). Similarly, tubular epithelial cell epithelial‐mesenchymal transition (EMT) induced by CsA toxicity resulted in the upregulation of microRNA‐494 and a decrease in PTEN levels in vitro. miR‐494 directly targeted Pten and negatively regulated its expression. Preventing Pten targeting by miR‐494 was sufficient to prevent CsA induced EMT. Knockdown of miR‐494 prevented the downregulation of PTEN in tubular epithelial cells following CsA treatment and also prevented CsA induced EMT. Thus, miR‐494 plays a major role in promoting CsA induced nephrotoxicity through its ability to target Pten thereby contributing to EMT. We suggest that manipulating miR‐494 expression may represent a novel approach to preventing EMT associated with CsA induced nephrotoxicity.     

Immunophenotypic Profile and Increased Risk of Hospital Admission for Infection in Infants Born to Female Kidney Transplant Recipients

Children born to female kidney recipients are exposed to immunosuppressive drugs during gestation. Little is known about their immune system at birth or in the long term. Twenty‐eight children born to female kidney recipients and 40 full‐term children born to healthy mothers were evaluated. T, B, NK, NKT, γδT cells were assessed by flow cytometry and functional evaluation of T and dendritic cells after in vitro activation was performed at birth and at 8 months of age. At birth, infants born to female kidney recipients showed lower numbers of CD4+ T, NKT and intense reduction of B cells (median cells/mm³, transplant: 153.7 X control: 512.4; p < 0.001). There was also a reduced percentage of activated CD8+ T and of CD4+ regulatory T cells. Activated memory and exhausted memory B cells showed higher percentages among children exposed to immunosuppressors when compared to control group. At 8 months, most immune alterations were no longer observed, but four children still had low numbers of some lymphocyte subsets at this age. Children born to female kidney recipients had 4.351 (95% CI: 1.026–15.225; p = 0.046) higher risk of hospital admission in the first months of life—some, with severe clinical manifestations—than those born to healthy women.     

Pathogen Stimulation History Impacts Donor‐Specific CD8+ T Cell Susceptibility to Costimulation/Integrin Blockade–Based Therapy

Recent studies have shown that the quantity of donor‐reactive memory T cells is an important factor in determining the relative heterologous immunity barrier posed during transplantation. Here, we hypothesized that the quality of T cell memory also potently influences the response to costimulation blockade‐based immunosuppression. Using a murine skin graft model of CD8⁺ memory T cell–mediated costimulation blockade resistance, we elicited donor‐reactive memory T cells using three distinct types of pathogen infections. Strikingly, we observed differential efficacy of a costimulation and integrin blockade regimen based on the type of pathogen used to elicit the donor‐reactive memory T cell response. Intriguingly, the most immunosuppression‐sensitive memory T cell populations were composed primarily of central memory cells that possessed greater recall potential, exhibited a less differentiated phenotype, and contained more multi‐cytokine producers. These data, therefore, demonstrate that the memory T cell barrier is dependent on the specific type of pathogen infection via which the donor‐reactive memory T cells are elicited, and suggest that the immune stimulation history of a given transplant patient may profoundly influence the relative barrier posed by heterologous immunity during transplantation.