Abstract: Introduction. Along with death engraftment, in recent years, antibody-mediated damage has been identified as the leading cause of loss of kidney transplants. Despite the recognition of the role of the B-lymphocyte subpopulation in the development of both tolerance and rejection, little is known about the trigger mechanisms and effectors of this humoral response. Background. We analyzed the relationship between B lymphocyte subpopulations and levels of B-cell?activating factor (BAFF) with the histological findings in biopsies of renal transplantation. Material and Methods. We selected 35 patients whose kidney transplant biopsy was performed between January and November 2015. The biopsy specimens were classified according to Banff criteria. At the moment of the biopsy BAFF levels and B-lymphocyte subpopulations in blood were measured using enzyme-linked immunosorbent assay (ELISA) and using flow cytometry, respectively. Results. Mean BAFF levels were 493 ± 245 pg/mL. The median performance of biopsy post-transplantation was 12.9 (11.7-23.9) months. BAFF levels correlated with pretransplantation antibodies (r = 0.523; P = .002) but not with kidney function. In biopsies performed more than 1 year after transplantation BAFF levels correlated with the severity of chronic glomerular (cg) involvement (r = 0.625; P = .003). Histological variables related to antibody-mediated injury selected by principal component analysis (glomerulitis, peritubular capillary, and chronic glomerulopathy) related to BAFF levels (B factor, 116; 95% confidence interval [CI], 12?220; P = .029). Biopsy specimens with transplant glomerulopathy (TG) showed lower levels of circulating naive CD19 + subpopulation, IgD+, and CD27- (32.7 ± 28.1 vs 87.9 ± 79.1; P = .017) compared with biopsy specimens without TG. Conclusions. Elevated levels of BAFF are associated with increased presence and severity of TG and a set of variables related to antibody-mediated histological damage. TG is associated with changes in circulating B-lymphocyte subpopulations that could contribute to its pathogenesis.

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