Expression of B-cell activating factor of the tumour necrosis factor family (BAFF) in T cells in active systemic lupus erythematosus: the role of BAFF in T cell-dependent B cell pathogenic autoantibody production.

OBJECTIVES: To determine whether B cell activating factor of the tumour necrosis factor family (BAFF) is involved in T cell-dependent B cell pathogenic autoantibody production in systemic lupus erythematosus (SLE).
METHODS: Peripheral blood mononuclear cells (PBMCs) from 23 SLE patients were analysed by flow cytometry to examine the intracellular expression of BAFF in CD4+ and CD8+ T cells and the surface expression of BAFF-receptor (R) and TACI on CD20+ B cells. Moreover, peripheral blood was used to determine the level of BAFF messenger RNA (mRNA) in CD4+ and CD8+ T cells and the level of BAFF-R mRNA in CD20+ B cells. Blocking of BAFF function with TACI-Ig measured anti-double-stranded DNA (dsDNA) antibodies by enzyme-linked immunosorbent assay (ELISA).
RESULTS: CD4+ and CD8+ T cells from patients with active SLE expressed intracellular BAFF whereas those from normal subjects did not. BAFF-R and TACI were expressed on B cells from both normal controls and patients with active SLE and there was no significant difference. CD4+ and CD8+ T cells from SLE patients expressed BAFF mRNA whereas those from normal controls did not. Expression of BAFF-R mRNA in CD20+ B cells showed no significant difference between SLE patients and normal controls. TACI-Ig suppressed spontaneous in vitro T cell-dependent B cell anti-dsDNA antibodies production on active SLE with kidney involvement.
CONCLUSIONS: BAFF may play a pathogenic role in SLE by stimulating T cell-dependent B cell autoantibodies production. Blockade of BAFF is a promising therapeutic approach for SLE especially in patients with kidney involvement.