Late Plasma Cell Depletion After Thymoglobulin Induction in Kidney Transplant Recipients

OBJECTIVES: Induction therapy with rabbit antithymocyte globulin is frequently used in kidney transplant recipients and contributes to regulating the humoral alloantibody response. However, the effect of rabbit antithymocyte globulin on B-cell subpopulations, including plasma cells, has not been previously studied in humans in vivo. MATERIALS AND METHODS: We prospectively studied a cohort of 39 adult kidney transplant recipients. Twenty patients received rabbit antithymocyte globulin as induction therapy. Peripheral blood samples were obtained pretransplant and at 6 and 12 months posttransplant. T and B cells were acquired by flow cytometry. RESULTS: Total lymphocytes and CD3 and CD4 cells significantly decreased at 6 and 12 months only in patients who received rabbit antithymocyte globulin. In contrast, the CD19 population did not change after rabbit antithymocyte globulin induction. One-year circulating plasma cells remained significantly lower than pretransplant levels in patients who received rabbit antithymocyte globulin. We observed sig-nificant differences in plasma cell numbers at 12 months after transplant between patients who received rabbit antithymocyte globulin and those patients who did not receive it (median of 5 and interquartile range of 3-17 vs median of 25 and interquartile range of 12-35; P = .001). CONCLUSIONS: Rabbit antithymocyte globulin induction leads to a late reduction in the number of circulating plasma cells at 1 year after kidney transplant. This effect can contribute to down-regulation of the humoral alloantibody response.