IL10 and systemic lupus erythematosus: IL-10 is a key cytokine produced by Breg cells, and diminished disease severity was observed following administration of IL-10 in the NZM2410 mouse model of lupus [12], whereas more severe disease occurred in both MRL/lpr mice on a IL-10 KO background and in Breg cell-deficient NZB/W mice [13], [14].