MUL1 and systemic lupus erythematosus: Recent findings have elucidated a key mechanism for Treg dysfunction in SLE, demonstrating that deficient expression of the E3 ubiquitin ligase Cbl‐b impairs the K63‐linked polyubiquitination of STAT‐3, leading to its hyper‐phosphorylation and the characteristic “resistance to suppression” phenotype [316].