The Impact of Reduced Immunosuppression on Alloimmunity: A Retrospective Study of Pediatric Kidney Transplant Recipients

ABSTRACT Background Kidney transplantation is the best treatment for end‐stage kidney disease but requires immunosuppressive medications, which have significant side effects. Many pediatric recipients experience these side effects, leading to dosage reductions, which potentially increase the risk of alloimmunity. We aimed to describe the alteration in immunosuppressive medication, explore the reasons for the reductions, and assess the potential impact on alloimmunity. Method Data from 49 pediatric kidney transplant recipients receiving an allograft from 2009 to 2020 were retrospectively studied. The recipients were screened for HLA antibodies after the transplantation. Results The median age of recipients was 11 years (IQR 8), with a median follow‐up of 5 years (IQR 5). Eighty percent of the transplantations were corticosteroid‐free. During follow‐up, 11% developed de novo donor‐specific antibodies (dnDSA), and 60% had detectable HLA antibodies. The 1‐year rejection rate was 4%. Immunosuppressive medication was altered substantially in most recipients, resulting in 72% being on mono‐ or dual therapy with a reduced mycophenolate mofetil (MMF) dosage by the end of the first posttransplant year. The median MMF dose was nearly half of the intended. Tacrolimus levels were maintained close to the target of 5 ng/mL. No association was found between reduced immunosuppression and dnDSA or rejections. Reductions were primarily due to MMF‐related side effects: leukopenia in 77%, gastrointestinal issues in 34%, and infections with Epstein–Barr virus, cytomegalovirus, and BK polyomavirus in 49%. Conclusions Reduced MMF with a sufficient trough tacrolimus level in a population of mainly corticosteroid‐free pediatric kidney transplant recipients did not lead to unacceptable alloimmunity. Reduced mycophenolate mofetil with a sufficient trough tacrolimus level in a population of mainly corticosteroid‐free pediatric kidney transplant recipients did not lead to unacceptable alloimmunity.