Eileen W. Tsai

CD20+ lymphocytes in renal allografts are associated with poor graft survival in pediatric patients.

Background. The presence of CD20+ lymphocyte renal allograft infiltrates has been associated with steroid-resistant rejection and poor graft survival. We quantified the number of CD20+ lymphocytes in renal allograft biopsies and correlated the results with graft survival. We also determined the relationships between CD20+ lymphocytes and acute cellular rejection versus antibody-mediated rejection. Methods. We examined 45 biopsy samples from 31 pediatric patients biopsied for suspicion of rejection from November 2001 to November 2004. Immunohistochemical staining for CD20 and C4d was performed on all biopsies; CD20+ cell density per high-power field (hpf) was determined for each core. Patient graft status was followed postbiopsy and documented for graft survival or failure using the cutoff date of December 31, 2005. Results. Patients with 2–10 and 11–100 CD20+ cells/hpf had worse graft survival in Kaplan-Meier analysis with a hazard ratio 4.56 (CI 1.07–19.35) two years postbiopsy compared to those with 0–1 cells/hpf (P=0.02). The presence of CD20+ lymphocytes was significantly associated with acute cellular rejection (P=0.0001) and not associated with antibody-mediated rejection (P=0.16). Receiver-operating curve analysis confirmed ≥3 cells/hpf correlating with acute cellular rejection, yielding sensitivity 90% and specificity 76%. Conclusions. This study shows a significant 4.5-fold risk of graft failure at two years postbiopsy with presence of ≥2 CD20+ cells/hpf. Moreover, ≥3 CD20+ lymphocytes were highly associated with acute cellular rejection. They may be functioning as professional antigen-presenting cells in the graft. In steroid-refractory cellular rejections, therapies that target B cells may prolong graft survival.

Monitoring nonadherence and acute rejection with variation in blood immunosuppressant levels in pediatric renal transplantation.

Background. Acute rejection associated with medication nonadherence is a major cause of allograft loss in pediatric kidney transplant patients. There is currently no reliable method to detect medication nonadherence and prevent allograft rejection. Methods. In 46 pediatric patients who underwent renal transplantation between 2002 and 2003, the variation of serum drug levels was studied as a potential objective tool to monitor medication nonadherence. Tacrolimus (TAC) and mycophenolic acid (MPA) trough levels were measured from 1 to 12 months posttransplant, and standard deviation (SD) and percent coefficient of variation (CV%) were calculated. Because SD increased as mean trough levels rose, CV% (CV%=SD/mean multiplied by 100%) was used to eliminate this confounding effect. Results. Ten of 46 patients had biopsy-proven rejection. The median TAC CV% was 53.4% in patients with biopsy-proven rejection, which was significantly higher than 30% in those without rejection (P=0.005). Median MPA CV% was 51.9% in patients without rejection and 45.1% in patients with rejection (P=NS). High TAC CV% correlated with increased risk for rejection, whereas MPA CV% did not. Conclusion. The TAC CV% seems to be a useful and superior marker, compared with SD alone, for assessing medication nonadherence and the possibility of allograft rejection in pediatric renal transplantation.

Mineral abnormalities and long-term graft function in pediatric renal transplant recipients: a role for FGF-23?

BACKGROUND Although current guidelines recommend the evaluation of mineral and bone metabolism in patients with all stages of chronic kidney disease (CKD), the prevalence of altered mineral ion homeostasis in the pediatric posttransplant population is unknown. Moreover, the contribution of abnormal mineral ion metabolism to graft outcomes in this population has not been evaluated. METHODS Serum calcium, phosphorus, 25(OH)vitamin D, 1,25(OH)(2)vitamin D, parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF-23) levels were evaluated 4.9 ± 0.5 years after transplantation in 68 stable pediatric renal allograft recipients. Patients were subsequently followed for 2 years. RESULTS At baseline, mean estimated glomerular filtration rate (GFR) was 60 ± 2 mL/min/1.73 m(2). Serum calcium and phosphorus values were within the reference interval. PTH values were elevated but did not differ by CKD stage. 25(OH)vitamin D levels were low in nearly half of all subjects. Tubular reabsorption of phosphate and 1,25(OH)(2)vitamin D values were lower, while FGF-23 and PTH values were higher in more advanced stages of CKD. Thirty percent of patients with FGF-23 values >110 RU/mL had a decrease in GFR of >50% (P < 0.05) and FGF-23 values predicted future episodes of rejection. CONCLUSIONS Despite normal serum calcium and phosphorus levels in the majority of prevalent pediatric renal transplant recipients, abnormalities in PTH, 25(OH)vitamin D and FGF-23 are common. FGF-23 levels may be associated with increased risk for deterioration of kidney function and episodes of rejection.

Acute Rejection Associated with Donor-Specific Anti-MICA Antibody in a Highly Sensitized Pediatric Renal Transplant Recipient

Narayan S, Tsai EW, Zhang Q, Wallace WD, Reed EF, Ettenger RB. Acute rejection associated with donor‐specific anti‐MICA antibody in a highly sensitized pediatric renal transplant recipient.
Pediatr Transplantation 2011: 15:E1–E7.

A novel treatment regimen for BK viremia.

Background BK viremia, a prerequisite for BK virus nephropathy (BKVN), affects 5% to 16% of pediatric renal transplant recipients (PRTR). We evaluated the safety and efficacy of a novel approach to treating BK viremia using fluoroquinolones and leflunomide in PRTR. Methods We studied 230 PRTR at Mattel Children’s Hospital, UCLA, who underwent renal transplantation between January 2003 and October 2010. Nineteen patients were found to have BK viremia. Ciprofloxacin was started when the BK viral load was greater than 625 copies/mL, and patients were switched to leflunomide if BK viral load did not decrease after 2 months of ciprofloxacin therapy. All patients underwent transplant kidney biopsy, and their estimated glomerular filtration rate (eGFR) and BK PCR was measured serially. The side effects of ciprofloxacin and leflunomide were recorded in each patient. Results There was a significant decrease in BK viral load in patients treated with ciprofloxacin and leflunomide (P<0.001) with only a small reduction in immunosuppression. BK viremia was associated with a significantly decreased eGFR (P<0.001), and treatment with ciprofloxacin and leflunomide was associated with improved eGFR (P<0.001). This approach resulted in a BKVN rate of only 1%. Conclusions This analysis demonstrates for the first time that, used in a stepwise fashion, ciprofloxacin and leflunomide are effective and safe treatments for BK viremia in PRTR.

Accelerated rejection, thrombosis, and graft failure with angiotensin II type 1 receptor antibodies

BackgroundAngiotensin II type 1 receptor antibodies (AT1R-Abs) have been implicated in renal transplant rejection and failure; however, the mechanism of allograft damage, patterns of clinical presentation, and response to desensitization of AT1R-Abs have not been clearly established.Case diagnosis/treatmentWe present the case of a 7-year-old boy with preformed AT1R-Abs who developed accelerated vascular and cellular rejection and renal allograft thrombosis despite desensitization and treatment with angiotensin receptor blockade. Although an association between AT1R-Abs and microvascular occlusion has been previously described, we are the first to describe an association between AT1R-Abs and renal artery thrombosis, leading to devastating early allograft failure.ConclusionsThis case highlights the risk of allograft thrombosis associated with AT1R-Abs and illustrates that previous treatments utilized for AT1R-Abs may not always be effective. Further studies are needed to better characterize the mechanisms of AT1R-Ab pathogenesis and to establish safe levels of AT1R-Abs both pre- and post-transplantation. Given the outcome of this patient and the evidence of pro-coagulatory effects of AT1R-Abs, we suggest that the presence of AT1R-Ab may be a risk factor for thrombosis. The role of treatment with anti-coagulation and novel immunomodulatory agents such as tocilizumab and bortezomib require further investigation.

Significance of intragraft CD138+ lymphocytes and p-S6RP in pediatric kidney transplant biopsies.

Background. We have previously shown that intragraft CD20+ B cells are associated with acute cellular rejection (ACR) and allograft loss. Phosphorylation of S6 ribosomal protein, a downstream target of the PI3K/Akt/mTOR pathway, promotes growth and proliferation of cells and could identify metabolically active cells such as alloantibody secreting plasma cells. Because CD20+ lymphocytes can differentiate into CD138+ plasma cells, we aimed to identify functionally active plasma cells by using intragraft CD138 quantification and p-S6RP staining and correlate these results with allograft rejection, function, and survival. Methods. We examined 46 renal transplant biopsies from 32 pediatric patients who were biopsied for clinical suspicion of rejection. Immunohistochemical staining for C4d, CD20, CD138, and p-S6RP was performed. Patient creatinine clearance and graft status was followed up postbiopsy. Results. Patients with greater than or equal to six CD138+ cells/high power field (hpf) had worse graft survival with a hazard ratio of 3.4 (95% CI 1.3–9.2) 2 years postbiopsy compared with those with 0 to 5 cells/hpf (P=0.016). CD138+ cells were stained for p-S6RP, indicating functionally active plasma cells. They were associated with ACR (P=0.004) and deteriorating graft function (R2=0.22, P=0.001). Intragraft CD20+ and CD138+ cells found together in ACR were associated with poorer graft survival than either marker alone, hazard ratio 1.5 (95% CI 1.1–2.2, P=0.01). Conclusions. A threshold of greater than or equal to six CD138+ metabolically active plasma cells per hpf, coexisting with CD20+ B cells, was associated with poor allograft function and survival. This may represent an additional antibody-mediated process present in the setting of ACR and could play an important role in characterization and treatment of transplant rejection.

New priorities: Analysis of the New Kidney Allocation System on UCLA patients transplanted from the deceased donor waitlist.

UNOS implemented a new Kidney Allocation System (New KAS) on December 4, 2014 with a primary goal of increasing equity to organ transplant for patients that were immunologically or socially disadvantaged by the previous allocation system (Previous KAS) that prioritized long wait times. We examined the effects of the New KAS on patients transplanted from the UCLA deceased donor waitlist during the first year and compared to the last year of the Previous KAS. The total number of deceased donor kidney transplants was increased in the New KAS as compared to the Previous KAS (178 vs 148). Transplant of regraft patients and of highly sensitized patients with cPRA⩾99% was significantly increased in the New KAS (New KAS vs Previous KAS, 29.8% vs 11.5%, p⩽0.0001, and 26.4% vs 2.7%, p⩽0.0001, respectively). In the New KAS, the percentage of patients receiving allografts imported from outside our local area was also significantly increased (34.8% vs 15.5%, p<0.0001). In the New KAS, 59.7% and 48.3% of imported organs were allocated to very highly sensitized (⩾99% cPRA) or re-graft patients, respectively, as compared to 8.7% and 8.7% during the Previous KAS (p<0.001). Recipients and donors with age differences exceeding 15years were decreased in the New KAS as compared to the Previous KAS (36.5 vs 48.7%, p⩽0.032). There was a 40.1% reduction in transplant to patients in the 65+ age group in the New KAS (p⩽0.025). The percentage of patients transplanted with preformed donor specific antibody (DSA) was similar in the New as compared to the Previous KAS (19.7% vs 15.5%) and, patients were transplanted with a range of 1-3 preformed DSA of weak to moderate strength. Cold ischemic time was significantly increased over all organs, and in patients transplanted with preformed DSA during the New as compared to the Previous KAS (17.5 vs 19.1h and 17.2 vs 22.2, p<0.04 and p<0.03, respectively). Episodes of delayed graft function and the number of biopsies for cause were similar between the New and the Previous KAS. However, there were more events of biopsy proven antibody mediated rejection in patients transplanted since the start of the New KAS. The data show that the New KAS is working at the center level as designed to better age match recipients and donors and to increase transplantation of very highly sensitized patients through broader sharing.

A paradigm shift and a few modest suggestions in the care of adolescent transplant recipients.

Well over 50% of pediatric renal transplants are performed in adolescents (1). Numerous studies have demonstrated that, although those transplanted as adolescents have the best 3-month and 1-year graft survival among all age groups (including all adult age groups), the 5-year graft outcome is among the worst of all age groups (2, 3). Although helpful in a general way, studies that classify pediatric patients according to age groupings at the time of transplant have obvious methodologic shortcomings. When, for example, a group of patients 13 to 18 years old are considered, it is impossible to know at what specific age individual patients run into trouble with their graft function. For in pediatrics, it is not the age at which a patient is transplanted that is relevant so much as it is the age at which the patient begins to experience medical complications. In this issue of Transplantation, Foster et al. (4) have written a seminal article which more precisely identifies the ages at which adolescents experience graft loss. This article uses the huge United States Renal Data System database and control for time posttransplant in their analysis. The authors demonstrate that beginning at approximately 9 years of age, adolescent patients experience year to year graft loss at an ever increasing rate until it peaks at an age of 19 to 20 years. They also demonstrate that in children younger than 12 years old, the rate of graft loss increases dramatically over the late posttransplant period. The greatest incidence of graft failure occurs in patients aged 17 to 24 years. Foster et al. found that, in young children at the time of transplant, the highest rate of graft failure occurred some 13 to 17 years posttransplant, whereas higher failure rates were found in the years immediately following transplant among those transplanted during adolescence (4). The reasons underlining these findings are by no means obvious because the process of graft loss in pediatric transplantation is not a straightforward process. The most obvious explanation of the findings of Foster et al. is medication nonadherence. The undeniable characteristic of pediatric transplant medicine is that patients go though a stepwise progression of physical, psychologic, and immunobiologic changes. The developmental tasks that the adolescent must accomplish are well documented. Adolescents are navigating the difficult task of establishing individuality, while still being somewhat dependant on their family. The importance of peer pressure to not appear different, the difficulty of thinking abstractly rather than concretely, and the emerging issues of sexuality, all of these help contribute to the adolescent’s vulnerability when it comes to medication administration. This is certainly not helped by the omnipresent ambivalence of the family when it comes to deciding how much and when to give increased levels of freedom to the adolescent. Unfortunately, the level of research dealing with adolescent medication nonadherence (and truth to tell, all of nonadherence) leaves the clinician wanting as to how to confront it. There is ambiguity as to the definition (how much nonadherence is enough to eventuate in graft damage), the best method(s) to detect nonadherence, and the approach(es) to ameliorate it (5). A discussion of adolescent nonadherence is beyond the scope of this short commentary. But it is important to remember that nonadherent behavior is a pattern established over a long period of time and often doesn’t manifest itself clinically until pathologic processes (acute and chronic rejection) are far along in their evolution. The process of graft loss in the adolescent and the young adult may be accentuated by other immunobiologic processes. Human immune responses vary considerably from individual to individual, and it is increasingly clear that this variability is dynamic and continually influenced by one’s response to environmental pathogens, particularly viruses (6 –10). It is hypothesized that exposure to viruses, particularly herpes viruses, expands an individual’s alloreactivity repertoire. Because most young children are naïve to the herpes viruses, they experience these viruses over time, frequently during adolescence. In short, adolescents may become more immune reactive at different times as they mature and experience vial infection. Thus, while it is tempting to ascribe graft failure in adolescence to nonadherence, it is important to recognize that the results of Foster et al. may relate as much to an unfortuitous intersection of immune maturation with the developmental variability of the adolescent. Thus, there are two potential sides to consider: less consistent This work was supported in part by the Casey Lee Ball Foundation. The authors declare no conflicts of interest. 1 Division of Pediatric Nephrology, Mattel Children’s Hospital, UCLA, Los Angeles, CA. 2 Department of Pediatrics, State University of New York, Stoneybrook, NY. Address correspondence to: Robert B. Ettenger, M.D., Mattel Children’s Hospital, UCLA, UCLA Center for the Health Sciences, A2-383, 10833 Le Conte Ave, Los Angeles, CA 90095. E-mail: REttenger@mednet.ucla.edu Each of the authors contributed to the conception and writing of this manuscript. Received 15 September 2011. Accepted 20 September 2011. Copyright

MHC class I signaling: new functional perspectives for an old molecule

Donor-specific antibodies are associated with refractory rejection episodes and poor allograft outcomes in solid organ transplantation. Our understanding of antibody-mediated allograft injury is expanding beyond complement deposition. In fact, unique mechanisms of alloantibodies are advancing our knowledge about transplant vasculopathy and antibody-mediated rejection. These include direct effects on the endothelium, resulting in the recruitment of leukocytes, chemokine and cytokine production, and stimulation of innate and adaptive alloresponses. These effects will be the focus of the following review.