Alterations of naïve and memory B‐cell subsets are associated with risk of rejection and infection in heart recipients

Rejection and infection are relevant causes of mortality in heart recipients. We evaluated the kinetics of the maturation status of B lymphocytes and its relationship with acute cellular rejection and severe infection in heart recipients. We analyzed B-cell subsets using 4-color flow cytometry in a prospective follow-up study of 46 heart recipients. Lymphocyte subsets were evaluated at specific times before and up to 1 year after transplantation. Higher percentages of pretransplant class-switched memory B cells (CD19+CD27+IgM-IgD- >14%) were associated with a 74% decrease in the risk of severe infection [Cox regression relative hazard (RH) 0.26, 95% confidence interval (CI), 0.07–0.86; P = 0.027]. Patients with higher percentages of naive B cells at day 7 after transplantation (CD19+CD27-IgM+IgD+ >58%) had a 91% decrease in the risk of developing acute cellular rejection (RH 0.09; 95% CI, 0.01–0.80; P = 0.02). Patients with infections showed a strong negative correlation between baseline serum B-cell–activating factor (BAFF) concentration and absolute counts of memory class-switched B cells (R = −0.81, P = 0.01). The evaluation of the immunophenotypic maturation status of B lymphocytes could prove to be a useful marker for identifying patients at risk of developing rejection or infection after heart transplantation.