Supplementary Material for: Acute Antibody-Mediated Rejection Associated with Anti-MICA Antibodies in Long-Term Kidney Transplant: A Case Study

Introduction: Advances in immunosuppressive therapy have improved kidney transplant outcomes; however, antibody-mediated rejection (ABMR) still affects graft survival. Herein, we present a case of a 46-year-old woman who experienced acute ABMR despite stable long-term graft function following kidney transplantation. Case Presentation: At 28 years of age, she underwent a blood-type-compatible living kidney transplant from her father. Eighteen years later, she was admitted to the hospital with a fever and sore throat, raising suspicion of a respiratory infection. Given the rapid deterioration of renal function following hospitalisation, a biopsy was conducted. The findings showed diffuse glomerulitis and peritubular capillaritis, along with focal observations of endoarteritis, glomerular thrombi, and interstitial haemorrhage, consistent with active ABMR. She was treated with methylprednisolone pulse therapy and intravenous immunoglobulin, which induced gradual recovery. Screening tests for anti-human leukocyte antigen (HLA) antibodies yielded negative results. However, tests for non-HLA antibodies detected the presence of anti-major histocompatibility complex class I chain-related gene A (MICA) antibodies in the blood sample prior to the onset of rejection. Notably, at the time of rejection, anti-MICA antibodies were not detectable in the blood; nevertheless, they were subsequently found to be positive 10 months later. These antibodies may have been sequestered within tissues, rendering them undetectable in the bloodstream. Conclusion: Anti-MICA antibodies have previously been implicated in ABMR; however, this case highlights their role in late-onset rejection after prolonged graft stability. This case underscores the importance of non-HLA donor-specific antibody tests when ABMR occurs in a recipient lacking anti-HLA antibodies.