Comprehensive Phenotyping and Cytokine Production of Circulating B Cells Associate Resting Memory B Cells With Early Antibody-mediated Rejection in Kidney Transplant Recipients

BACKGROUND: B cells play a crucial role in kidney transplantation through antibody production and cytokine secretion. To better understand their impact on kidney transplantation, this retrospective study aimed to characterize circulating B-cell phenotypes and cytokine production in a cohort of kidney transplant patients to identify whether pretransplant donor-specific antibodies (DSAs) or biopsy-proven rejection is associated with different B-cell profiles.

METHODS: Pretransplant cryopreserved peripheral blood mononuclear cells were obtained from 96 kidney transplant recipients, of whom 42 had pretransplant DSAs. The cells underwent surface marker staining using a 33-color spectral flow cytometry panel for B-cell phenotyping. Simultaneously, cells were stimulated for interleukin-10, tumor necrosis factor-α, and interleukin-6 production, and analyzed with a 6-color panel.

RESULTS: Rejection was linked to decreased naive B cells and increased plasmablasts, CD27+ memory B cells, and memory B-cell subsets (all P < 0.04) compared with no rejection. Cytokine-producing B cells and immune regulatory molecule expression showed no significant differences. Multivariate analysis identified resting memory B cells (CD27+CD21+) and pretransplant DSAs as significantly associated with rejection (P = 0.01; odds ratio [OR], 1.07; P = 0.02; OR, 3.10, respectively). Cox regression analysis revealed resting memory B cells were associated with early antibody-mediated rejection (P = 0.04; OR, 1.05).

CONCLUSIONS: B-cell subset distributions differed between patients with and without rejection. Resting memory B-cell frequency was associated with increased early antibody-mediated rejection risk, whereas cytokine production and immune checkpoint expression did not influence rejection. The results suggest that B-cell subset composition could aid in rejection risk assessment and serve as a potential pretransplant diagnostic parameter.