Active Chronic Sarcoidosis is Characterized by Increased Transitional Blood B Cells, Increased IL-10-Producing Regulatory B Cells and High BAFF Levels

Background

Sarcoidosis is a multisystemic disease of unknown etiology characterized by a disproportionate Th1 granulomatous immune response in the organs involved. Plasmatic hypergammaglobulinemia and B cell accumulation in granulomatous lesions suggest the possible role of humoral immune responses in the pathogenesis of sarcoidosis. The purpose of this study is to describe B cell peripheral compartment in sarcoidosis.

Methodology/Principal Findings

We analyzed blood B cell subsets and BAFF levels in 33 patients with chronic sarcoidosis (active sarcoidosis n?=?18; inactive sarcoidosis n?=?15) and 18 healthy donors. Active chronic sarcoidosis patients had significantly less circulating memory B cells (p<0.01), more transitional (p<0.01) and increased numbers of IL-10-producing regulatory B cells (p<0.05) compared with healthy donors and patients with inactive sarcoidosis. BAFF serum levels were significantly higher in patients with active sarcoidosis (p<0.01 versus healthy donors and inactive sarcoidosis patients) and strongly correlated with serum hypergammaglobulinemia (r?=?0.53, p<0.01) and angiotensin converting enzyme levels (r?=?0.61, p?=?<0.01).

Conclusions/Significance

These data show that there is an altered B cell homeostasis in active sarcoidosis and suggest BAFF antagonist drugs as potential new treatments of this disease.