IL10 and systemic lupus erythematosus: Unexpectedly, this cytokine was spontaneously produced by a fraction of B cells from the blood of untreated SLE patients (Fig. 1a), and the density of these IL-10+ B cells positively correlated with disease progression (Fig. 1b and Supplementary Fig. 1a) but declined in the blood of SLE patients with clinical remission or complete remission (Fig. 1a).