Treatment with TNFα blockers induces phenotypical and functional aberrations in peripheral B cells

To dissect the mechanisms of anti-TNFα-induced autoimmunity we examined the phenotype and function of B cells from anti-TNFα-treated patients. Levels of Lyn, Syk, SHP-1, tyrosine 348 phospho-Syk (Y348-Syk) and tyrosine phosphorylated (P-Y) proteins were evaluated and B-cell-surface CD20, CD21 and CD5 were also assessed in 29 patients treated with TNF-α blockers. Following treatment, Lyn, but not Syk or SHP-1, significantly increased particularly in patients with spondyloarthropathies. Increased Lyn levels following treatment correlated with increased Lyn activity as evidenced by a 2.9-fold increase of Y348-Syk (a Lyn target). Peripheral B-cells from 56.3% of the patients displayed a tendency towards increased P-Y levels without any BCR-initiated activation during treatment. CD20, but not CD21, significantly increased in patients with rheumatoid arthritis. Circulating CD5+ B-cells were also significantly expanded during treatment. Our findings suggest that B cells in anti-TNFα-treated patients display functional and phenotypical aberrations that may enhance our understanding of TNF-α blocker-induced autoimmunity.