*Purpose: The purpose of this study is to describe and evaluate treatment practices and patient outcomes for kidney transplant recipients with presence of C4d negative antibody mediated rejection (AMR) on kidney biopsy.

*Methods: This was a single center, retrospective cohort study of kidney transplant recipients. Patients were included in the study if they had a kidney biopsy performed between January 1, 2016 and November 30, 2019 that showed presence of C4d negative AMR. Patients who received treatment for C4d negative AMR had data collected at months 6 and 12 after the completion of treatment. Patients who did not receive treatment for C4d negative AMR had data collected at months 6 and 12 after their biopsy.

*Results: Ninety patients were screened for inclusion in this study. Sixty patients who were identified to have C4d negative AMR on kidney biopsy during the specified time period were included. Overall, 46 patients received treatment for C4d negative AMR while 14 did not receive treatment. There were no significant differences in baseline characteristics observed between groups. Treatment for C4d negative AMR consisted of weekly infusions of intravenous immunoglobulin (IVIG) for 31 patients (67.4%), plasma exchange followed by IVIG for 14 patients (30.4%) and plasma exchange followed by IVIG with 1 dose of rituximab for 1 patient (2.2%). When comparing those who received treatment and those who did not, there was not a significant difference in graft survival at month 6 (95.7% vs. 85.7%, p=0.23) or 12 (89.1% vs. 71.4%, p=0.19). In patients with a functioning graft, median change in serum creatinine was not statistically different at month 12 when comparing those who received treatment to those who did not (0.47 mg/dL vs. 0.31 mg/dL, p=0.76).

*Conclusions: This study describes treatment practices and patient outcomes of a cohort of kidney transplant recipients at our center who had C4d negative AMR on kidney biopsy. Majority of the patients in this study were treated with either weekly IVIG infusions or plasma exchange in combination with IVIG. Data from this cohort did not reveal a significant difference in change in serum creatinine or graft survival at 12 months for patients who received treatment for C4d negative AMR compared to those who did not.

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