The increased IL-10 level showed no correlations with IL-10+ Bregs or other Breg subsets, but it did correlate with SLE disease severity parameters, including C4 (negatively correlated) and CRP (positively correlated), suggesting that the total amount of circulating IL-10 plays a proinflammatory role in SLE. Here, CRP is linked to systemic lupus erythematosus.