sTNF-RII: is it useful for the early diagnosis of rejection and for prognosis after renal transplantation?

Characterization of putative regulatory isoforms of porcine tumor necrosis factor receptor 2 in endothelial cells

Tumor necrosis factor α (TNFα) and its receptors contribute to rejection of transplanted cells and organs. To elucidate how TNFα affects xenograft rejection, we previously cloned the cDNA of pig TNF-receptor 2 (pTNFR2) and found four isoforms: one comprising the full receptor with four cysteine-rich domains (CRD), a shorter variant (pTNFR2ΔE7-10) encoding for a soluble isoform, another lacking exon 4 (pTNFR2ΔE4) displaying only 3 CRD and poor ligand binding, and the smallest one generated by the two alternative splicings. All isoforms contained the pre-ligand assembly domain (PLAD) responsible for receptor trimerization. We now investigated their roles by structural, expression, and subcellular localization studies. Structural in silico analyses identified four amino acids potentially involved in TNFα binding and lacking in pTNFR2ΔE4. Quantitative RT-PCR determined regulated expression affecting the two pTNFR2 alternative splicings in cytokine-stimulated porcine aortic endothelial cells (PAEC). Particularly, human IL-1α and TNFα produced a strong mRNA upregulation of all isoforms, being the full receptor the predominant one. However, expression of pTNFR2 on PAEC did not correlate with mRNA and decreased after 24-hour exposure to IL-1α or TNFα. Notably, confocal microscopy confirmed the presence of pTNFR2 inside and on the plasma membrane, whereas pTNFR2ΔE4 located only intracellularly. Most interestingly, FRET analyses showed that membrane-bound isoforms pTNFR2 and pTNFR2ΔE4 colocalized intracellularly and associated through the PLAD. Our data show that pTNFR2ΔE4 bind and may retain the full receptor intracellularly. This mechanism has not been described in other species and represents a particularity that may affect the pathophysiology of pig xenografts.

Evidence-based diagnosis and treatment of macrophage activation syndrome in systemic juvenile idiopathic arthritis

BACKGROUND

Macrophage activation syndrome (MAS) is a severe and potentially lethal complication of several inflammatory diseases but seems particularly linked to systemic juvenile idiopathic arthritis (sJIA). Standardized diagnostic and treatment guidelines for MAS in sJIA are currently lacking. The aim of this systematic literature review was to evaluate currently available literature on diagnostic criteria for MAS in sJIA and provide an overview of possible biomarkers for diagnosis, disease activity and treatment response and recent advances in treatment.

METHODS

A systematic literature search was performed in MEDLINE, EMBASE and Cochrane. 495 papers were identified. Potentially relevant papers were selected by 3 authors after which full text screening was performed. All selected papers were evaluated by at least two independent experts for validity and level of evidence according to EULAR guidelines.

RESULTS

27 papers were included: 7 on diagnosis, 9 on biomarkers and 11 on treatment. Systematic review of the literature confirmed that there are no validated diagnostic criteria for MAS in sJIA. The preliminary Ravelli criteria, with the addition of ferritin, performed well in a large retrospective case-control study. Recently, an international consortium lead by PRINTO proposed a new set of diagnostic criteria able to distinguish MAS from active sJIA and/or infection with superior performance. Other promising diagnostic biomarkers potentially distinguish MAS complicating sJIA from primary and virus-associated hemophagocytic lymphohistiocytosis. The highest level of evidence for treatment comes from case-series. High dose corticosteroids with or without cyclosporine A were frequently reported as first-line therapy. From the newer treatment modalities, promising responses have been reported with anakinra.

CONCLUSION

MAS in sJIA seems to be diagnosed best by the recently proposed PRINTO criteria, although prospective validation is needed. Novel promising biomarkers for sJIA related MAS are in need of prospective validation as well, and are not widely available yet. Currently, treatment of MAS in sJIA relies more on experience than evidence based medicine. Taking into account the severity of MAS and the scarcity of evidence, early expert consultation is recommended as soon as MAS is suspected.

TNF receptors: signaling pathways and contribution to renal dysfunction

Tumor necrosis factor (TNF), initially reported to induce tumor cell apoptosis and cachexia, is now considered a central mediator of a broad range of biological activities from cell proliferation, cell death and differentiation to induction of inflammation and immune modulation. TNF exerts its biological responses via interaction with two cell surface receptors: TNFR1 and TNFR2. (TNFRs). These receptors trigger shared and distinct signaling pathways upon TNF binding, which in turn result in cellular outputs that may promote tissue injury on one hand but may also induce protective, beneficial responses. Yet the role of TNF and its receptors specifically in renal disease is still not well understood. This review describes the expression of the TNFRs, the signaling pathways induced by them and the biological responses of TNF and its receptors in various animal models of renal diseases, and discusses the current outcomes from use of TNF biologics and TNF biomarkers in renal disorders.

Tumor necrosis factor receptor 2: its contribution to acute cellular rejection and clear cell renal carcinoma

Tumor necrosis factor receptor 2 (TNFR2) is a type I transmembrane glycoprotein and one of the two receptors that orchestrate the complex biological functions of tumor necrosis factor (TNF, also designed TNF-α). Accumulating experimental evidence suggests that TNFR2 plays an important role in renal disorders associated with acute cellular rejection and clear cell renal carcinoma but its exact role in these settings is still not completely understood. This papers reviews the factors that may mediate TNFR2 induction in acute cellular rejection and clear cell renal carcinoma and its contribution to these conditions and discusses its therapeutic implications. A greater understanding of the function of TNFR2 may lead to the development of new anti-TNF drugs.

HLA class I (ABC) upregulation on peripheral blood CD3+/CD8+ T lymphocyte surface is a potential predictor of acute rejection in renal transplantation

BACKGROUND

Renal transplantation is currently the prevalent therapy for most patients with end-stage renal disease. No clinical markers for such rejection have been universally accepted. We aimed to investigate the possibility of use of human leukocyte antigen (HLA) class I (ABC) on peripheral blood CD3+/CD8+ T lymphocytes as a marker of acute rejection.

METHODS

For recipients undergoing renal transplantation from September 2007 to November 2008, peripheral blood samples were obtained pretransplantation and at days 3 and 7 posttransplantation when the patients were still hospitalized and at weeks 2 and 3 and months 1, 2, 3, and 6 posttransplantation. For patients with fever, lumbodynia, gross hematuria, or oliguria after transplantation, blood samples were collected immediately before and at days 3 and 7 after the administration of anti-inflammatory regents. The level of HLA class I (ABC) on peripheral-blood CD3+/CD8+ T lymphocytes was measured on flow cytometry.

RESULTS

For the 79 transplant recipients, the level of HLA class I (ABC) on peripheral-blood CD3+/CD8+ T lymphocytes was consistently elevated during the first 3 weeks after transplantation, declined gradually to pretransplantation levels, then tapered off and remained stable. Patients experiencing acute rejection (AR) or not after transplantation did not differ in level of HLA class I (ABC) up to 6-month follow-up, except at days 14 and 21 after transplantation, when the level was higher for patients experiencing AR (P<0.01).

CONCLUSIONS

Upregulation of HLA class I (ABC) on peripheral-blood CD3+/CD8+ T lymphocytes could be used as an accurate and reliable predictor of AR after renal transplantation.

Lymphocytic HLA-A mRNA is a reliable indicator of acute rejection in renal transplantation

BACKGROUND

Rejection in renal transplantation is the most frequent event causing transplant failure. It is important to identify parameters to predict rejection, which are helpful in a timely fashion.

METHODS

Fifty-nine renal transplant recipients were divided into two groups: group 1 (stable renal function) and group 2 (acute rejection episodes). The levels of HLA-A mRNA in peripheral blood lymphocytes (both pre- and posttransplantation) were measured by reverse transcriptase-polymerase chain reaction (RT-PCR) with glucose-6-phosphate dehydrogenase (G6PDH) as an internal reference. The TEST software was used to analyze the relative expressions of HLA-A mRNA.

RESULTS

There was no statistical significance between features of the two groups pretransplant versus normal controls. Posttransplant, the HLA-A mRNA levels decreased significantly compared to those of pretransplant and normal control individuals. The levels of HLA-A mRNA among the 10 patients with acute rejection episodes were significantly increased. There was no significant change in the lymphocyte populations in the early stage of an acute rejection episode compared with the prerejection value.

CONCLUSION

HLA-A mRNA expression was strongly correlated with immune status. The HLA-A mRNA levels may provide an effective and reliable indicator to predict acute rejection episodes in renal transplantation.