Frequencies of circulating B-cell subpopulations before kidney transplantation identify patients at risk of acute rejection.

The response mediated by B lymphocytes has a crucial impact on kidney transplantation due to the role of anti–human leukocyte antigen antibodies in rejection and the contradictory observation of high B-lymphocyte numbers in tolerant kidney transplant recipients. The basis of the contradiction could lay in the different function of B-cell subsets depending on their degree of differentiation. We ought to measure circulating B-lymphocyte percentages in patients with end-stage renal disease before kidney transplantation to identify those with a high risk of acute rejection. Eighty patients on the waiting list for kidney transplantation followed up in our center were recruited from 2010, and samples were taken just before kidney transplantation. Eleven of 80 patients presented an episode of acute rejection (13.75%) and had an increased frequency of switched (SW) B cells compared with the rejection-free group (median [interquartile range] 24.5% [18.6% to 39.6%] vs 15.1 [8.45% to 23.4%]; P = .025). Subsequently, the frequency of SW B cells was assessed as a predicting factor of acute rejection. A value higher than 18.4% predicted patients at risk of suffering an acute rejection episode with a sensitivity of 81.8% and a specificity of 60.9% and an area under the curve of 71.2%. Moreover, a decrease in naïve B-cell subsets was related to patients at risk of acute rejection. The percentage of circulating B-cell subsets before kidney transplantation could be used as biomarker of risk to suffer acute rejection. These unicenter data must be validated in multicenter studies.