Objectives

Regulatory B cells (Bregs) and T cells (Tregs) are thought to be involved in the regulation of graft acceptance in renal transplant recipients. However, mechanisms that affect Breg differentiation and interaction with Tregs are rather unclear.

Methods

Using eight‐color‐fluorescence flow cytometry, Tregs and CD19+ CD24hiCD38hi Bregs were analyzed in whole blood samples of 80 stable kidney transplant recipients, 20 end‐stage renal disease (ESRD) patients and 32 healthy controls (HC). In addition, differentiation of Bregs and Tregs was studied in different micromilieus using cocultures with strongly enriched B‐lymphocytes and autologous peripheral blood mononuclear cells stimulated with CpG and phytohemagglutinin.

Results

Bregs were higher in HC than in ESRD patients and lowest in transplant recipients. Bregs were higher early as compared to late posttransplant. Posttransplant, high Bregs