Anti-BAFF treatment interferes with humoral responses in a model of renal transplantation in rats

BACKGROUND: B-cell-activating factor (BAFF) is associated with donor-specific antibodies (DSA) and poorer outcomes after renal transplantation (RTx). We examined the effects of anti-BAFF treatment on B cells, expression of costimulatory molecules and cytokines, germinal centers (GCs), and DSA formation in an RTx model in rats. METHODS: Anti-BAFF antibody was injected on days 3, 17, 31, and 45 after allogeneic RTx. Rats received reduced dose cyclosporine A for 28 or 56 days to allow chronic rejection and DSA formation. Leukocytes, B-cell subsets, and DSA were measured using flow cytometry; expression of cytokines and costimulatory molecules was measured by quantitative polymerase chain reaction, and GCs and T follicular helper were assessed using immunohistochemistry. Rejection was evaluated by a nephropathologist. RESULTS: Anti-BAFF treatment reduced the frequency of B cells in allografts and spleen. Naive B cells were strongly reduced by anti-BAFF treatment in all compartments. Messenger RNA expression of interleukin-6 and the costimulatory molecules CD40 and inducible T cell costimulator ligand was significantly reduced in anti-BAFF-treated rats. GC area was smaller and plasmablasts/plasma cell numbers lower in anti-BAFF-treated rats, which was reflected by less DSA in certain IgG subclasses. CONCLUSIONS: Anti-BAFF treatment interferes with humoral responses at multiple levels in this model of allogeneic RTx.