TRIM21 and synovial sarcoma: It was suggested [155] that, in SS and SLE, the triggering of autoimmunity might be favoured both by an intrinsic susceptibility of leukocytes to apoptosis [156]–[159], possibly due to the overexpression of the E3 ubiquitin ligase SS-A1/Ro52 [160], and by an impaired efferocytosis of apoptotic cells by macrophages [158]–[161].