Official reprint from UpToDate®
www.uptodate.com ©2017 UpToDate, Inc. and/or its affiliates. All Rights Reserved.

Immunosuppression in renal transplantation in children

Ruth A McDonald, MD
Section Editor
Patrick Niaudet, MD
Deputy Editor
Melanie S Kim, MD


The major advance allowing prolonged allograft survival in pediatric renal transplantation has been the use of immunosuppressive drugs that down-regulate the immune response. The goal remains to find the best combination of immunosuppressive agents that optimizes allograft survival by preventing acute rejection while limiting drug toxicities. Although data from adult renal transplantation trials are used to help guide management decisions in pediatric patients, immunosuppression often must be modified because of the unique clinical effects of some of these agents in children, including their impact on growth and development.

An overview of immunosuppression regimens used in children undergoing renal transplantation will be reviewed here. Additional issues concerning transplantation in children as well as detailed discussions of immunosuppressive issues in renal transplantation common to both children and adults are presented separately. (See "General principles of renal transplantation in children" and "Outcomes of renal transplantation in children" and "Maintenance immunosuppressive therapy in renal transplantation in adults" and "Induction immunosuppressive therapy in renal transplantation in adults".)


The goal of immunosuppression is to prevent acute rejection while minimizing drug side effects. In children who undergo renal transplantation, immunosuppression is divided into the three following categories:

Induction therapy – Intensive immunosuppression administered during the perioperative period to prevent acute rejection

Maintenance therapy – Immunosuppressive therapy to prevent acute rejection after the perioperative period

To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information on subscription options, click below on the option that best describes you:

Subscribers log in here

Literature review current through: Nov 2017. | This topic last updated: Jul 14, 2017.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2017 UpToDate, Inc.
  1. Benfield MR, McDonald RA, Bartosh S, et al. Changing trends in pediatric transplantation: 2001 Annual Report of the North American Pediatric Renal Transplant Cooperative Study. Pediatr Transplant 2003; 7:321.
  2. Benfield MR, Tejani A, Harmon WE, et al. A randomized multicenter trial of OKT3 mAbs induction compared with intravenous cyclosporine in pediatric renal transplantation. Pediatr Transplant 2005; 9:282.
  3. Feld LG, Stablein D, Fivush B, et al. Renal transplantation in children from 1987-1996: the 1996 Annual Report of the North American Pediatric Renal Transplant Cooperative Study. Pediatr Transplant 1997; 1:146.
  4. Grenda R, Watson A, Vondrak K, et al. A prospective, randomized, multicenter trial of tacrolimus-based therapy with or without basiliximab in pediatric renal transplantation. Am J Transplant 2006; 6:1666.
  5. Offner G, Toenshoff B, Höcker B, et al. Efficacy and safety of basiliximab in pediatric renal transplant patients receiving cyclosporine, mycophenolate mofetil, and steroids. Transplantation 2008; 86:1241.
  6. NAPRTCS 2008 annual report. https://web.emmes.com/study/ped/index.htm (Accessed on July 20, 2010).
  7. Kreis H. Antilymphocyte globulins in kidney transplantation. Kidney Int Suppl 1992; 38:S188.
  8. Khositseth S, Matas A, Cook ME, et al. Thymoglobulin versus ATGAM induction therapy in pediatric kidney transplant recipients: a single-center report. Transplantation 2005; 79:958.
  9. Chavers BM, Chang YC, Gillingham KJ, Matas A. Pediatric kidney transplantation using a novel protocol of rapid (6-day) discontinuation of prednisone: 2-year results. Transplantation 2009; 88:237.
  10. Li L, Chaudhuri A, Chen A, et al. Efficacy and safety of thymoglobulin induction as an alternative approach for steroid-free maintenance immunosuppression in pediatric renal transplantation. Transplantation 2010; 90:1516.
  11. Warejko JK, Hmiel SP. Single-center experience in pediatric renal transplantation using thymoglobulin induction and steroid minimization. Pediatr Transplant 2014; 18:816.
  12. Norman DJ, Leone MR. The role of OKT3 in clinical transplantation. Pediatr Nephrol 1991; 5:130.
  13. Seikaly M, Ho PL, Emmett L, Tejani A. The 12th Annual Report of the North American Pediatric Renal Transplant Cooperative Study: renal transplantation from 1987 through 1998. Pediatr Transplant 2001; 5:215.
  14. Niaudet P, Jean G, Broyer M, Chatenoud L. Anti-OKT3 response following prophylactic treatment in paediatric kidney transplant recipients. Pediatr Nephrol 1993; 7:263.
  15. Bartosh SM, Knechtle SJ, Sollinger HW. Campath-1H use in pediatric renal transplantation. Am J Transplant 2005; 5:1569.
  16. Shapiro R, Zeevi A, Basu A, et al. Alemtuzumab preconditioning with tacrolimus monotherapy-the impact of serial monitoring for donor-specific antibody. Transplantation 2008; 85:1125.
  17. Tan HP, Kaczorowski D, Basu A, et al. Steroid-free tacrolimus monotherapy after pretransplantation thymoglobulin or Campath and laparoscopy in living donor renal transplantation. Transplant Proc 2005; 37:4235.
  18. Shapiro R, Basu A, Tan H, et al. Kidney transplantation under minimal immunosuppression after pretransplant lymphoid depletion with Thymoglobulin or Campath. J Am Coll Surg 2005; 200:505.
  19. Sung J, Barry JM, Jenkins R, et al. Alemtuzumab induction with tacrolimus monotherapy in 25 pediatric renal transplant recipients. Pediatr Transplant 2013; 17:718.
  20. Kaabak MM, Babenko NN, Samsonov DV, et al. Alemtuzumab induction in pediatric kidney transplantation. Pediatr Transplant 2013; 17:168.
  21. Supe-Markovina K, Melquist JJ, Connolly D, et al. Alemtuzumab with corticosteroid minimization for pediatric deceased donor renal transplantation: a seven-yr experience. Pediatr Transplant 2014; 18:363.
  22. Kim IK, Choi J, Vo AA, et al. Safety and Efficacy of Alemtuzumab Induction in Highly Sensitized Pediatric Renal Transplant Recipients. Transplantation 2017; 101:883.
  23. Ona ET, Danguilan RA, Africa J, et al. Use of alemtuzumab (Campath-1H) as induction therapy in pediatric kidney transplantation. Transplant Proc 2008; 40:2226.
  24. Webb NJ, Prokurat S, Vondrak K, et al. Multicentre prospective randomised trial of tacrolimus, azathioprine and prednisolone with or without basiliximab: two-year follow-up data. Pediatr Nephrol 2009; 24:177.
  25. Grenda R, Watson A, Trompeter R, et al. A randomized trial to assess the impact of early steroid withdrawal on growth in pediatric renal transplantation: the TWIST study. Am J Transplant 2010; 10:828.
  26. Sarwal MM, Vidhun JR, Alexander SR, et al. Continued superior outcomes with modification and lengthened follow-up of a steroid-avoidance pilot with extended daclizumab induction in pediatric renal transplantation. Transplantation 2003; 76:1331.
  27. Opelz G, Naujokat C, Daniel V, et al. Disassociation between risk of graft loss and risk of non-Hodgkin lymphoma with induction agents in renal transplant recipients. Transplantation 2006; 81:1227.
  28. Pape L, Strehlau J, Henne T, et al. Single centre experience with basiliximab in paediatric renal transplantation. Nephrol Dial Transplant 2002; 17:276.
  29. Clark G, Walsh G, Deshpande P, Koffman G. Improved efficacy of basiliximab over antilymphocyte globulin induction therapy in paediatric renal transplantation. Nephrol Dial Transplant 2002; 17:1304.
  30. Offner G, Broyer M, Niaudet P, et al. A multicenter, open-label, pharmacokinetic/pharmacodynamic safety, and tolerability study of basiliximab (Simulect) in pediatric de novo renal transplant recipients. Transplantation 2002; 74:961.
  31. Kovarik JM, Offner G, Broyer M, et al. A rational dosing algorithm for basiliximab (Simulect) in pediatric renal transplantation based on pharmacokinetic-dynamic evaluations. Transplantation 2002; 74:966.
  32. Höcker B, Kovarik JM, Daniel V, et al. Pharmacokinetics and immunodynamics of basiliximab in pediatric renal transplant recipients on mycophenolate mofetil comedication. Transplantation 2008; 86:1234.
  33. Sterkers G, Baudouin V, Ansart-Pirenne H, et al. Duration of action of a chimeric interleukin-2 receptor monoclonal antibody, basiliximab, in pediatric kidney transplant recipients. Transplant Proc 2000; 32:2757.
  34. Nayak AB, Ettenger RB, McGuire S, et al. Optimizing HLA matching in a highly sensitized pediatric patient using ABO-incompatible and paired exchange kidney transplantation. Pediatr Nephrol 2015; 30:855.
  35. Stojanovic J, Adamusiak A, Kessaris N, et al. Immune Desensitization Allows Pediatric Blood Group Incompatible Kidney Transplantation. Transplantation 2016.
  36. Dobbels F, Ruppar T, De Geest S, et al. Adherence to the immunosuppressive regimen in pediatric kidney transplant recipients: a systematic review. Pediatr Transplant 2010; 14:603.
  37. Korsch BM, Fine RN, Negrete VF. Noncompliance in children with renal transplants. Pediatrics 1978; 61:872.
  38. Kirsham RL, Panayi GS. Steroids. In: Immunopharmacology in Autoummune diseases and Transplantation, Rugstad HE, Endressen L, Forre O (Eds), Plenum Press, New York 1992. p.103.
  39. Beato M. Gene regulation by steroid hormones. Cell 1989; 56:335.
  40. Paliogianni F, Raptis A, Ahuja SS, et al. Negative transcriptional regulation of human interleukin 2 (IL-2) gene by glucocorticoids through interference with nuclear transcription factors AP-1 and NF-AT. J Clin Invest 1993; 91:1481.
  41. Broyer M, Guest G, Gagnadoux MF. Growth rate in children receiving alternate-day corticosteroid treatment after kidney transplantation. J Pediatr 1992; 120:721.
  42. Jabs K, Sullivan EK, Avner ED, Harmon WE. Alternate-day steroid dosing improves growth without adversely affecting graft survival or long-term graft function. A report of the North American Pediatric Renal Transplant Cooperative Study. Transplantation 1996; 61:31.
  43. Benfield MR, Bartosh S, Ikle D, et al. A randomized double-blind, placebo controlled trial of steroid withdrawal after pediatric renal transplantation. Am J Transplant 2010; 10:81.
  44. Höcker B, Weber LT, Feneberg R, et al. Prospective, randomized trial on late steroid withdrawal in pediatric renal transplant recipients under cyclosporine microemulsion and mycophenolate mofetil. Transplantation 2009; 87:934.
  45. Tsampalieros A, Knoll GA, Molnar AO, et al. Corticosteroid Use and Growth After Pediatric Solid Organ Transplantation: A Systematic Review and Meta-Analysis. Transplantation 2017; 101:694.
  46. McDonald RA, Smith JM, Ho M, et al. Incidence of PTLD in pediatric renal transplant recipients receiving basiliximab, calcineurin inhibitor, sirolimus and steroids. Am J Transplant 2008; 8:984.
  47. Höcker B, Weber LT, Feneberg R, et al. Improved growth and cardiovascular risk after late steroid withdrawal: 2-year results of a prospective, randomised trial in paediatric renal transplantation. Nephrol Dial Transplant 2010; 25:617.
  48. Webb NJ, Douglas SE, Rajai A, et al. Corticosteroid-free Kidney Transplantation Improves Growth: 2-Year Follow-up of the TWIST Randomized Controlled Trial. Transplantation 2015; 99:1178.
  49. Sarwal MM, Ettenger RB, Dharnidharka V, et al. Complete steroid avoidance is effective and safe in children with renal transplants: a multicenter randomized trial with three-year follow-up. Am J Transplant 2012; 12:2719.
  50. Chavers BM, Rheault MN, Gillingham KJ, Matas AJ. Graft loss due to recurrent disease in pediatric kidney transplant recipients on a rapid prednisone discontinuation protocol. Pediatr Transplant 2012; 16:704.
  51. Bach JF. Mode of action of thiopurines: Azathioprine and 6-mercaptopurine. In: Immunopharmacology in Autoimmune Diseases and Transplantation, Rugstad HE, Endressen L, Forre O (Eds), Plenum Press, New York 1992. p.123.
  52. Buell JF, Gross TG, Woodle ES. Malignancy after transplantation. Transplantation 2005; 80:S254.
  53. Allison AC, Eugui EM, Sollinger HW. Mycophenolate mofetil (RS-61443): Mechanisms of action and effects in transplantation. Transplant Rev 1993; 7:129.
  54. Placebo-controlled study of mycophenolate mofetil combined with cyclosporin and corticosteroids for prevention of acute rejection. European Mycophenolate Mofetil Cooperative Study Group. Lancet 1995; 345:1321.
  55. Sollinger HW. Mycophenolate mofetil for the prevention of acute rejection in primary cadaveric renal allograft recipients. U.S. Renal Transplant Mycophenolate Mofetil Study Group. Transplantation 1995; 60:225.
  56. A blinded, randomized clinical trial of mycophenolate mofetil for the prevention of acute rejection in cadaveric renal transplantation. The Tricontinental Mycophenolate Mofetil Renal Transplantation Study Group. Transplantation 1996; 61:1029.
  57. Jungraithmayr TC, Wiesmayr S, Staskewitz A, et al. Five-year outcome in pediatric patients with mycophenolate mofetil-based renal transplantation. Transplantation 2007; 83:900.
  58. Cransberg K, Marlies Cornelissen EA, Davin JC, et al. Improved outcome of pediatric kidney transplantations in the Netherlands -- effect of the introduction of mycophenolate mofetil? Pediatr Transplant 2005; 9:104.
  59. Höcker B, Weber LT, Bunchman T, et al. Mycophenolate mofetil suspension in pediatric renal transplantation: three-year data from the tricontinental trial. Pediatr Transplant 2005; 9:504.
  60. Ferraris JR, Tambutti ML, Redal MA, et al. Conversion from azathioprine [correction of azathioprina] to mycophenolate mofetil in pediatric renal transplant recipients with chronic rejection. Transplantation 2000; 70:297.
  61. Henne T, Latta K, Strehlau J, et al. Mycophenolate mofetil-induced reversal of glomerular filtration loss in children with chronic allograft nephropathy. Transplantation 2003; 76:1326.
  62. Borrows R, Chusney G, Loucaidou M, et al. Mycophenolic acid 12-h trough level monitoring in renal transplantation: association with acute rejection and toxicity. Am J Transplant 2006; 6:121.
  63. Tredger JM, Brown NW. Mycophenolate: better value through monitoring? Transplantation 2006; 81:507.
  64. Kuypers DR, Le Meur Y, Cantarovich M, et al. Consensus report on therapeutic drug monitoring of mycophenolic acid in solid organ transplantation. Clin J Am Soc Nephrol 2010; 5:341.
  65. Weber LT, Shipkova M, Armstrong VW, et al. The pharmacokinetic-pharmacodynamic relationship for total and free mycophenolic Acid in pediatric renal transplant recipients: a report of the german study group on mycophenolate mofetil therapy. J Am Soc Nephrol 2002; 13:759.
  66. Mourad M, Malaise J, Chaib Eddour D, et al. Correlation of mycophenolic acid pharmacokinetic parameters with side effects in kidney transplant patients treated with mycophenolate mofetil. Clin Chem 2001; 47:88.
  67. Le Meur Y, Büchler M, Thierry A, et al. Individualized mycophenolate mofetil dosing based on drug exposure significantly improves patient outcomes after renal transplantation. Am J Transplant 2007; 7:2496.
  68. Gaston RS, Kaplan B, Shah T, et al. Fixed- or controlled-dose mycophenolate mofetil with standard- or reduced-dose calcineurin inhibitors: the Opticept trial. Am J Transplant 2009; 9:1607.
  69. Van Gelder T, Silva HT, de Fijter H, et al. A prospective, randomized study comparing fixed dose vs concentration controlled MMF regimens for de nova patients following renal transplantation (the FDCC trial). Am J Transplant 2006; 6:343.
  70. Bunchman T, Navarro M, Broyer M, et al. The use of mycophenolate mofetil suspension in pediatric renal allograft recipients. Pediatr Nephrol 2001; 16:978.
  71. Butani L, Palmer J, Baluarte HJ, Polinsky MS. Adverse effects of mycophenolate mofetil in pediatric renal transplant recipients with presumed chronic rejection. Transplantation 1999; 68:83.
  72. Höcker B, van Gelder T, Martin-Govantes J, et al. Comparison of MMF efficacy and safety in paediatric vs. adult renal transplantation: subgroup analysis of the randomised, multicentre FDCC trial. Nephrol Dial Transplant 2011; 26:1073.
  73. Pape L, Ahlenstiel T, Kreuzer M, Ehrich JH. Improved gastrointestinal symptom burden after conversion from mycophenolate mofetil to enteric-coated mycophenolate sodium in kidney transplanted children. Pediatr Transplant 2008; 12:640.
  74. Vilalta Casas R, Vila López A, Nieto Rey JL, et al. Mycophenolic Acid reaches therapeutic levels whereas mycophenolate mofetil does not. Transplant Proc 2006; 38:2400.
  75. Tejani A, Stablein DM, Donaldson L, et al. Steady improvement in short-term graft survival of pediatric renal transplants: the NAPRTCS experience. Clin Transpl 1999; :95.
  76. Colombani PM, Dunn SP, Harmon WE, et al. Pediatric transplantation. Am J Transplant 2003; 3 Suppl 4:53.
  77. Tejani A, Ho PL, Emmett L, et al. Reduction in acute rejections decreases chronic rejection graft failure in children: a report of the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS). Am J Transplant 2002; 2:142.
  78. Kahan BD. Cyclosporine. N Engl J Med 1989; 321:1725.
  79. Harmon WE, Sullivan EK. Cyclosporine dosing and its relationship to outcome in pediatric renal transplantation. Kidney Int Suppl 1993; 43:S50.
  80. Harmon WE, McDonald RA, Reyes JD, et al. Pediatric transplantation, 1994-2003. Am J Transplant 2005; 5:887.
  81. Magee JC, Bucuvalas JC, Farmer DG, et al. Pediatric transplantation. Am J Transplant 2004; 4 Suppl 9:54.
  82. Klintmalm GB. FK 506: an update. Clin Transplant 1994; 8:207.
  83. Shaw LM, Holt DW, Keown P, et al. Current opinions on therapeutic drug monitoring of immunosuppressive drugs. Clin Ther 1999; 21:1632.
  84. Birk PE, Cook ME, Schmidt WJ, Chavers BM. Preliminary experience with FK 506 in pediatric renal transplant recipients: a single-center report. Transplant Proc 1996; 28:993.
  85. Shapiro R. Tacrolimus in pediatric renal transplantation: a review. Pediatr Transplant 1998; 2:270.
  86. Shapiro R, Scantlebury VP, Jordan ML, et al. FK506 in pediatric kidney transplantation--primary and rescue experience. Pediatr Nephrol 1995; 9 Suppl:S43.
  87. McKee M, Segev D, Wise B, et al. Initial experience with FK506 (tacrolimus) in pediatric renal transplant recipients. J Pediatr Surg 1997; 32:688.
  88. Neu AM, Ho PL, Fine RN, et al. Tacrolimus vs. cyclosporine A as primary immunosuppression in pediatric renal transplantation: a NAPRTCS study. Pediatr Transplant 2003; 7:217.
  89. Trompeter R, Filler G, Webb NJ, et al. Randomized trial of tacrolimus versus cyclosporin microemulsion in renal transplantation. Pediatr Nephrol 2002; 17:141.
  90. Filler G, Webb NJ, Milford DV, et al. Four-year data after pediatric renal transplantation: a randomized trial of tacrolimus vs. cyclosporin microemulsion. Pediatr Transplant 2005; 9:498.
  91. Ellis D. Clinical use of tacrolimus (FK-506) in infants and children with renal transplants. Pediatr Nephrol 1995; 9:487.
  92. Ciancio G, Siquijor AP, Burke GW, et al. Post-transplant lymphoproliferative disease in kidney transplant patients in the new immunosuppressive era. Clin Transplant 1997; 11:243.
  93. Dharnidharka VR, Ho PL, Stablein DM, et al. Mycophenolate, tacrolimus and post-transplant lymphoproliferative disorder: a report of the North American Pediatric Renal Transplant Cooperative Study. Pediatr Transplant 2002; 6:396.
  94. Hoyer PF, Ettenger R, Kovarik JM, et al. Everolimus in pediatric de nova renal transplant patients. Transplantation 2003; 75:2082.
  95. Kahan BD, Julian BA, Pescovitz MD, et al. Sirolimus reduces the incidence of acute rejection episodes despite lower cyclosporine doses in caucasian recipients of mismatched primary renal allografts: a phase II trial. Rapamune Study Group. Transplantation 1999; 68:1526.
  96. Kahan BD, Podbielski J, Napoli KL, et al. Immunosuppressive effects and safety of a sirolimus/cyclosporine combination regimen for renal transplantation. Transplantation 1998; 66:1040.
  97. Kahan BD, Camardo JS. Rapamycin: clinical results and future opportunities. Transplantation 2001; 72:1181.
  98. Schachter AD, Meyers KE, Spaneas LD, et al. Short sirolimus half-life in pediatric renal transplant recipients on a calcineurin inhibitor-free protocol. Pediatr Transplant 2004; 8:171.
  99. Sindhi R, Webber S, Goyal R, et al. Pharmacodynamics of sirolimus in transplanted children receiving tacrolimus. Transplant Proc 2002; 34:1960.
  100. Kreis H, Cisterne JM, Land W, et al. Sirolimus in association with mycophenolate mofetil induction for the prevention of acute graft rejection in renal allograft recipients. Transplantation 2000; 69:1252.
  101. Hymes LC, Warshaw BL. Sirolimus in pediatric patients: results in the first 6 months post-renal transplant. Pediatr Transplant 2005; 9:520.
  102. Schwartz C, Oberbauer R. Calcineurin inhibitor sparing in renal transplantation. Curr Opin Organ Transplant 2006; 11:632.
  103. Harmon W, Meyers K, Ingelfinger J, et al. Safety and efficacy of a calcineurin inhibitor avoidance regimen in pediatric renal transplantation. J Am Soc Nephrol 2006; 17:1735.
  104. Höcker B, Feneberg R, Köpf S, et al. SRL-based immunosuppression vs. CNI minimization in pediatric renal transplant recipients with chronic CNI nephrotoxicity. Pediatr Transplant 2006; 10:593.
  105. Hymes LC, Warshaw BL, Amaral SG, Greenbaum LA. Tacrolimus withdrawal and conversion to sirolimus at three months post-pediatric renal transplantation. Pediatr Transplant 2008; 12:773.
  106. Weintraub L, Li L, Kambham N, et al. Patient selection critical for calcineurin inhibitor withdrawal in pediatric kidney transplantation. Pediatr Transplant 2008; 12:541.
  107. Ettenger R, Hoyer PF, Grimm P, et al. Multicenter trial of everolimus in pediatric renal transplant recipients: results at three year. Pediatr Transplant 2008; 12:456.
  108. Pape L, Offner G, Kreuzer M, et al. De novo therapy with everolimus, low-dose ciclosporine A, basiliximab and steroid elimination in pediatric kidney transplantation. Am J Transplant 2010; 10:2349.
  109. Pape L, Lehner F, Blume C, Ahlenstiel T. Pediatric kidney transplantation followed by de novo therapy with everolimus, low-dose cyclosporine A, and steroid elimination: 3-year data. Transplantation 2011; 92:658.
  110. Grushkin C, Mahan JD, Mange KC, et al. De novo therapy with everolimus and reduced-exposure cyclosporine following pediatric kidney transplantation: a prospective, multicenter, 12-month study. Pediatr Transplant 2013; 17:237.
  111. Ferraresso M, Belingheri M, Ginevri F, et al. Three-yr safety and efficacy of everolimus and low-dose cyclosporine in de novo pediatric kidney transplant patients. Pediatr Transplant 2014; 18:350.
  112. Sayegh MH, Turka LA. The role of T-cell costimulatory activation pathways in transplant rejection. N Engl J Med 1998; 338:1813.
  113. www.nulojix.com/pdf/NulojixApprovalPlus/REMS%20Educational%20Deck.pdf (Accessed on September 22, 2015).
  114. McDonald R, Ho PL, Stablein DM, et al. Rejection profile of recent pediatric renal transplant recipients compared with historical controls: a report of the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS). Am J Transplant 2001; 1:55.