Serum levels of BAFF are increased in bullous pemphigoid but not in pemphigus vulgaris

BAFF [B-cell activating factor belonging to the tumour necrosis factor (TNF) family] is a member of the TNF superfamily that regulates B-lymphocyte proliferation and survival. It has been demonstrated that increased levels of soluble BAFF are associated with systemic autoimmunity in patients with systemic lupus erythematosus, rheumatoid arthritis and Sjogren's syndrome, and in animal models of spontaneous autoimmune diseases. However, the significance of circulating BAFF in autoimmune bullous diseases is unknown. To examine whether BAFF levels are elevated in the autoimmune blistering diseases pemphigus vulgaris (PV) and bullous pemphigoid (BP). We examined sera obtained from 21 patients with PV, 39 patients with BP and 22 healthy donors. We performed enzyme-linked immunosorbent assays for soluble BAFF and each disease-specific antibody: antidesmoglein-3 antibody for PV and anti-BP180 antibody for BP. Significant elevations of serum BAFF levels were found in the patients with BP, but not with PV. There was apparently no significant association between the serum BAFF levels and titres of anti-BP180 antibodies in the patients with BP. However, serum BAFF levels tended to be more elevated in patients with a shorter disease duration. There was a tendency that BAFF levels increased before the anti-BP180 antibody levels increased at the onset of BP and quickly decreased in response to treatment. BAFF may be a useful marker for early activation of an autoimmune diathesis and may play a critical role in triggering activation of self-antigen-driven autoreactive B cells in BP.