IFNL1 and systemic lupus erythematosus: Similar to type I IFNs, serum levels of IFN-λ1 are elevated in SLE patients and, more importantly, are positively correlated with lupus disease activity and anti-dsDNA levels, as well as being negatively correlated with complement level [109], perhaps partially due to an IFN-λ1-mediated increase in the level of Th17-derived cytokines [110] (Figure 3).