Longitudinal Analysis of T and B Cell Phenotype and Function in Renal Transplant Recipients with or without Rituximab Induction Therapy

Background: Prevention of rejection after renal transplantation requires treatment with immunosuppressive drugs. Data on their in vivo effects on T-and B-cell phenotype and function are limited. Methods: In a randomized double-blind placebo-controlled study to prevent renal allograft rejection, patients were treated with tacrolimus, mycophenolate mofetil (MMF), steroids, and a single dose of rituximab or placebo during transplant surgery. In a subset of patients, we analyzed the number and phenotype of peripheral T and B cells by multiparameter flow cytometry before transplantation, and at 3, 6, 12, and 24 months after transplantation. Results: In patients treated with tacrolimus/MMF/steroids the proportion of central memory CD4(+) and CD8(+) T cells was higher at 3 months post-transplant compared to pre-transplant levels. In addition, the ratio between the percentage of central memory CD4(+) and CD4(+) regulatory T cells was significantly higher up to 24 months post-transplant compared to pre-transplant levels. Interestingly, treatment with tacrolimus/MMF/steroids resulted in a shift toward a more memory-like B-cell phenotype post-transplant. Addition of a single dose of rituximab resulted in a long-lasting B-cell depletion. At 12 months post-transplant, the small fraction of repopulated B cells consisted of a high percentage of transitional B cells. Rituximab treatment had no effect on the T-cell phenotype and function post-transplant. Conclusions: Renal transplant recipients treated with tacrolimus/MMF/steroids show an altered memory T and B-cell compartment post-transplant. Additional B-cell depletion by rituximab leads to a relative increase of transitional and memory-like B cells, without affecting T-cell phenotype and function.