High urine sIL-6R as a predictor of late graft failure in renal transplant recipients

Impact of interleukin-6 on T cells in kidney transplant recipients

Interleukin-6 (IL-6), a multifunctional proinflammatory cytokine, plays a key role in T cell activation, survival, and differentiation. Acting as a switch that induces the differentiation of naïve T cells into Th17 cells and inhibits their development into regulatory T cells, IL-6 promotes rejection and abrogates tolerance. Therapies that target IL-6 signaling include antibodies to IL-6 and the IL-6 receptor and inhibitors of janus kinases; several of these therapeutics have demonstrated robust clinical efficacy in autoimmune and inflammatory diseases. Clinical trials of IL-6 inhibition in kidney transplantation have focused primarily on its effects on B cells, plasma cells, and HLA antibodies. In this review, we summarize the impact of IL-6 on T cells in experimental models of transplant and describe the effects of IL-6 inhibition on the T cell compartment in kidney transplant recipients.

Interleukin-6 blockade with tocilizumab increases Tregs and reduces T effector cytokines in renal graft inflammation: A randomized controlled trial

Interleukin-6 (IL-6) is a proinflammatory cytokine and key regulator of Treg: T effector cell (Teff) balance. We hypothesized that IL-6 blockade with tocilizumab, a monoclonal antibody to IL-6R, would increase Tregs, dampen Teff function, and control graft inflammation. We conducted a randomized controlled clinical trial (2014-2018) of clinically stable kidney transplant recipients on calcineurin inhibitor, mycophenolate mofetil, and prednisone, with subclinical graft inflammation noted on surveillance biopsies during the first year posttransplant. Subjects received tocilizumab (8 mg/kg IV every 4 weeks; 6 doses; n = 16) or no treatment (controls; n = 14) on top of usual maintenance immunosuppression. Kidney biopsies pre- and post-treatment were analyzed using Banff criteria. Blood was analyzed for serum cytokines, Treg frequencies, and T cell effector molecule expression (IFN-γ, IL-17, granzyme B) post-stimulation ex vivo. Tocilizumab-treated subjects were more likely to show improved Banff ti-score (62.5% vs. 21.4%, p = .03), increased Treg frequency (7.1% ± 5.55% vs. 3.6% ± 1.7%, p = .0168), and a blunted Teff cytokine response compared to controls. Changes in Banff i- and t-scores were not significantly different. The treatment was relatively well tolerated with no patient deaths or graft loss. Blockade of IL-6 is a novel and promising treatment option to regulate the T cell alloimmune response in kidney transplant recipients. NCT02108600.

Peri- and Postoperative Treatment with the Interleukin-1 Receptor Antagonist Anakinra Is Safe in Patients Undergoing Renal Transplantation: Case Series and Review of the Literature

In patients undergoing solid organ transplantation, the presence of an interleukin-1 (IL-1) driven disease may require the addition of IL-1 inhibiting drugs to the standard immunosuppressive regimen to protect against inflammation and negative graft outcome. Three patients undergoing renal transplantation were treated perioperatively with the interleukin-1 receptor antagonist anakinra. Kidney function increased rapidly in all three and the only complications seen were minor infections. In vitro studies report associations between serum and urinary levels of IL-1β and IL-1 receptor antagonist and negative graft outcome, and studies in animals and two small human trials illustrate a possible protective effect of anti-IL-1 therapy after solid organ transplantation. Peri- and postoperative use of anakinra is safe and effective in patients undergoing renal transplantation.

Inflammation-associated graft loss in renal transplant recipients

BACKGROUND

Although short-term graft survival has improved substantially in renal transplant recipients, long-term graft survival has not improved over the last decades. The lack of knowledge of specific causes and risk factors has hampered improvements in long-term allograft survival. There is an uncertainty if inflammation is associated with late graft loss.

METHODS

We examined, in a large prospective trial, the inflammation markers high-sensitivity C-reactive protein (hsCRP) and interleukin-6 (IL-6) and their association with chronic graft dysfunction. We collected data from the Assessment of Lescol in Renal Transplant trial, which recruited 2102 maintenance renal transplant recipients.

RESULTS

Baseline values were hsCRP 3.8 ± 6.7 mg/L and IL-6 2.9 ± 1.9 pg/mL. Adjusted for traditional risk factors, hsCRP and IL-6 were independently associated with death-censored graft loss, the composite end points graft loss or death and doubling of serum creatinine, graft loss or death.

CONCLUSION

The inflammation markers hsCRP and IL-6 are associated with long-term graft outcomes in renal transplant recipients.

Urinary proinflammatory cytokine response in renal transplant recipients with polyomavirus BK viruria

BACKGROUND

Polyomavirus BK (BKV) has emerged as an important complication after kidney transplantation. BKV-associated nephropathy develops in approximately 5% to 8% of renal transplant recipients, and its prognosis is poor. The relationship between urine cytokines and BK viruria in kidney recipients has not been defined.

PATIENTS AND METHODS

We compared posttransplant urine cytokine levels of 65 renal transplant outpatients with (BK-positive) or without BK viruria (BK-negative, n=33), low- (n=16) or high-level (n=16) BK viral load (VL), and 24 healthy controls (HCs). Soluble interleukin-1 receptor antagonist (sIL-1RA), interleukin (IL)-2, sIL-2R, IL-3, IL-4, IL-6, sIL-6R, IL-10, IL-17, transforming growth factor-beta2, interferon-gamma, and tumor necrosis factor-alpha levels were determined using commercially available ELISA kits.

RESULTS

BK-positive patients showed higher urine IL-3 (P=0.006), sIL-6R (P=0.010), IL-6 (P=0.020), and sIL-1RA (P=0.050) than BK-negative patients. Compared with HCs, BK-negative patients had lower urine sIL-1RA (P=0.003), sIL-6R (P=0.001), and IL-17 (P<0.001), whereas BK-positive patients had higher urine IL-3 (P=0.004) and IL-6 (P=0.001) and lower IL-17 (P<0.001), suggesting cytokine suppression by immunosuppression and upregulation by BK-infection. Urine sIL-6R (P=0.003) and IL-6 (P=0.010) were higher in patients with high VL than in patients with low VL. Additionally, patients with high VL showed higher urine IL-6 (P=0.001), sIL-6R (P=0.001), sIL-1RA (P=0.016), and IL-3 (P=0.047) than BK-negative patients, and higher urine IL-6 (P<0.001) and lower IL-17 (P<0.001) than HCs.

CONCLUSION

BK-positive renal transplant recipients, especially those with high VL, showed strong inflammatory cytokine responses with increases of urine sIL-1RA, IL-3, IL-6, and sIL-6R. Our data suggest that monocyte- and Th-2-induced cytokines are involved in the pathogenesis of BKV-associated nephropathy.

Elevated serum interleukin-6 (IL-6) in solid-organ transplant recipients is positively associated with tissue destruction and IL-6 gene expression in the periodontium

BACKGROUND

The number of transplanted solid organs and life expectancy after transplantation are steadily rising worldwide. Inflammation is widely recognized as playing a pivotal role in transplant rejection, and several studies have shown that serum interleukin-6 (IL-6) levels can identify individuals who are at greater risk for rejection. Given the known association between IL-6 and chronic periodontitis, the aim of our study was to assess the periodontal status of solid-organ transplant subjects compared to systemically healthy controls, to quantify the IL-6 levels in the serum and periodontal tissues, and to explore their association.

METHODS

Forty-seven heart and kidney transplant and 18 systemically healthy age-matched individuals were recruited. Subjects received a complete periodontal examination, and blood and periodontal tissue samples were collected for quantification of IL-6 protein and mRNA levels, respectively.

RESULTS

Transplant subjects had significantly higher serum IL-6 levels and slightly but statistically significantly increased mean probing depths than healthy controls. Multivariable linear regression analysis adjusting for gender, diabetes, smoking, and immunosuppressant dose showed that the mean probing depth, number of missing teeth, and mean percentage of sites with > or =4 mm attachment loss were independent predictors for elevated serum IL-6 levels. Transplant subjects with chronic periodontitis had higher mean serum IL-6 levels than those without chronic periodontitis, and there was a positive correlation between periodontal IL-6 gene expression levels and serum IL-6 protein levels.

CONCLUSIONS

Periodontal tissue destruction and local IL-6 synthesis are associated with elevated serum IL-6 levels in transplant recipients. This may have serious implications in solid-organ transplant deterioration and chronic rejection.

Developing a tool for noninvasive monitoring of renal allografts

Renal transplantation has emerged as the therapy of choice for many patients with end-stage renal disease. One of the major goals is to tailor immunosuppressive therapy to the individual needs of every patient at every time point post transplant, balancing the risk for rejection and over-immunosuppression. Such individualized treatment will require assays that can detect harmful processes in the allograft early and that can be measured repeatedly. In this review, advantages and disadvantages of current assays to monitor renal allografts noninvasively and how proteomic technology might contribute to the development of novel biomarkers to improve patient management will be discussed.

Association of high pretransplant sIL-6R plasma levels with acute tubular necrosis in kidney graft recipients

BACKGROUND

Delayed graft function is primarily caused by acute tubular necrosis (ATN). We studied in renal transplant recipients with posttransplant graft biopsy whether an up-regulated immune system in the recipient immediately before transplantation affects the risk of developing ATN and might be relevant for the pathogenesis of ATN.

METHODS

In a retrospective study, we analyzed pretransplant and early posttransplant soluble interleukin (sIL)-1RA, interleukin (IL)-2, sIL-2R, IL-3, IL-4, IL-6, sIL-6R, IL-10, tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta2, interferon (IFN)-gamma, and neopterin plasma levels in patients with ATN (n=26). Matched patients with acute rejection (AR) (n=26) or normal posttransplant biopsy (n=26) served as controls.

RESULTS

Pretransplant sIL-6R was higher (P=0.0004) and pretransplant TGF-beta2 lower (P=0.002) in patients with ATN than in patients with normal biopsy. ROC curves showed that high pretransplant sIL-6R has a high sensitivity (77%) and high specificity (64%) for ATN (P=0.002). Posttransplant plasma sIL-6R continued to be higher in ATN patients than in patients with normal biopsy (P=0.001). Patients with acute rejection showed pre- and posttransplant sIL-6R and TGF-beta2 plasma levels similar to those of patients with normal biopsy (P=NS).

CONCLUSION

High pretransplant sIL-6R plasma levels are associated with an increased risk of ATN and might contribute to the development of ATN early posttransplant. Our data suggest that preactivation of the recipient's immune system increases the risk of ATN.

Urinary β2-Microglobulin Is Associated With Acute Renal Allograft Rejection

BACKGROUND

Identifying urinary biomarkers associated with acute rejection (AR) of kidney allografts could improve recipient care by allowing AR to be diagnosed noninvasively and treated earlier. We attempted to identify novel biomarkers associated with AR by analyzing urinary proteins by using matrix-associated laser desorption ionization time-of-flight mass spectroscopy (MALDI-TOF MS).

METHODS

Using MALDI-TOF MS, we analyzed urine samples from 30 renal allograft recipients with biopsy-proven AR, 15 allograft recipients without AR, preoperative samples from 29 kidney donors, and 10 subjects with proteinuric native kidney disease.

RESULTS

In samples obtained at the time of AR, we identified a protein peak at 11.7 kd that correlated strongly with AR. In regard to its predictive power for AR, this protein peak showed sensitivity of 83.3%, specificity of 80%, positive predictive value of 89%, and negative predictive value of 70.6%, suggesting that this protein is highly associated with AR. We identified this peak as being beta2-microglobulin. This was validated by using enzyme-linked immunosorbent assay, which documented the presence of high urinary beta2-microglobulin levels in subjects with AR.

CONCLUSION

Beta2-microglobulin could be a strong biomarker for AR if used in conjunction with other biomarkers, producing an AR-specific urinary protein signature. This possibility must be confirmed in a larger cohort of kidney transplant recipients.