Objective: To determine serum levels of BAFF, a potent B cell survival factor, in patients with systemic sclerosis (SSc) and relate the results to the clinical features of SSc.
Methods: Serum BAFF levels in 83 patients with SSc were examined by enzyme-linked immunosorbent assay (ELISA). In a longitudinal study, 131 serum samples obtained from 21 patients with SSc were analyzed. The expression of BAFF messenger RNA (mRNA) in the skin was quantified by real-time reverse transcription-polymerase chain reaction. The expression of BAFF receptor (BAFFR) on CD19+ B cells was assessed by flow cytometry. The production of IgG and interleukin-6 (IL-6) by isolated B cells was examined by ELISA.
Results: Serum BAFF levels were elevated in SSc patients compared with healthy controls and correlated positively with the extent of skin fibrosis. Among the 21 patients with SSc in the longitudinal study, 7 had decreased BAFF levels, 11 had levels that remained unchanged, and 3 patients had increased levels. Decreasing BAFF levels were accompanied by regression of skin sclerosis, whereas increasing levels of BAFF were associated with the new onset or worsening of organ involvement. BAFF mRNA expression was up-regulated in the affected skin of patients with early diffuse cutaneous SSc. BAFFR expression on B cells was increased in SSc patients relative to healthy controls. Furthermore, SSc B cells that were stimulated by BAFF exhibited an enhanced ability to produce IgG and IL-6.
Conclusion: These results suggest that BAFF and its signaling in B cells contribute to B cell abnormalities and disease development in patients with SSc.