Effect of end-stage renal disease on B-lymphocyte subpopulations, IL-7, BAFF and BAFF receptor expression

BACKGROUND: End-stage renal disease (ESRD) results in increased susceptibility to infections, impaired response to vaccination and diffuse B-cell lymphopenia. However, the precise nature and mechanism of ESRD-induced B-cell lymphopenia remains unclear. Therefore, we studied the distribution of major B-cell subsets, B-cell growth, differentiation and survival factors, IL-7 and BAFF, and their receptors in 21 haemodialysis patients and 21 controls. METHODS: Innate B1 cells (CD19+, CD5+), conventional B2 cells (CD19+, CD5-), newly formed transitional B cells (CD19+, CD10+, CD27-), naïve B cells (CD19+, CD27-) and memory B cells (CD19+, CD27+) and BAFF receptor were quantified by flow cytometry. Plasma IL-7, BAFF, IL-6, TNF-alpha and IL-10 were measured by ELISA. RESULTS: The ESRD group exhibited significant reductions of all B-cell subpopulations except for transitional B cells that were less severely affected. No significant difference was found in B-cell apoptosis between the ESRD and control groups. Moreover, plasma IL-7 and BAFF levels were elevated in ESRD patients, therefore excluding their deficiencies as a possible culprit. However, BAFF receptor expression was significantly reduced in transitional but not mature B cells in the ESRD group. Interestingly, B-cell activation with the TLR9 agonist resulted in significantly greater production of IL-6 and TNF alpha but not IL-10 in the ESRD group. CONCLUSIONS: Thus, despite elevation of B-cell growth, differentiation and survival factors, ESRD patients exhibited diffuse reduction of B-cell subpopulations. This was associated with the down-regulation of BAFF receptor in transitional B cells. The latter can, in part, contribute to B-cell lymphopenia by promoting resistance to the biological actions of BAFF that is a potent B-cell differentiation and survival factor.