*Purpose: Rituximab, which suppresses antibody production, is widely used for desensitization in ABO-incompatible and donor-specific antibody-positive kidney transplantation. However, data regarding the effects of individual differences in rituximab-induced B cell suppression on antibody-mediated rejection (AMR) and allograft function remain limited. Therefore, we aimed to evaluate association CD19-positive rate and AMR after kidney transplantation.

*Methods: Overall, 42 patients who received rituximab therapy for pretransplant desensitization in ABO-incompatible (n = 33) and donor-specific antibody-positive (n = 15) kidney transplantation were retrospectively observed. To predict AMR incidence, the peripheral blood CD19-positive rate was determined using the ROC curve and classified into short-acting and long-acting groups. AMR incidence, serum creatinine level, neutropenia incidence, cytomegalovirus antigenemia-positive rate, and rituximab dose were compared between the two groups.

*Results: Eight patients (19%) developed AMR within 38 months after transplantation. The CD19-positive rate at 6, 12, and 18 months after transplantation was found to be a risk factor of AMR. The CD19-positive rate cut-off value for predicting AMR was 4.4%, 6.4%, and 7.7% at 6, 12, and 18 months after transplantation, respectively. On comparing the short-acting and long-acting groups stratified according to the CD19-positive rate cut-off value, AMR incidence was significantly higher in the short-acting group than in the long-acting group at 6 months (71.4% vs. 8.6%, P = 0.0012), 12 months (70.0% vs. 3.1%, P < 0.001), and 18 months (58.3% vs. 3.3%, P < 0.001) after transplantation. The CD19-positive rate of all patients with AMR exceeded the cut-off value at either time of 6, 12, or 18 months. Conversely, the serum creatinine level, neutropenia incidence, cytomegalovirus antigenemia-positive rate, and rituximab dose showed no significant differences between the two groups at each time point.

*Conclusions: The risk of AMR following kidney transplantation is higher in patients with short-term B cell suppression following rituximab administration. Additional rituximab administration may prevent AMR in patients with a CD19-positive rate greater than the cut-off value.

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