C2 and systemic lupus erythematosus: The complement system also plays a crucial role in SLE pathogenesis, particularly components such as C1QA, C1QB, C2, and C3, which are essential for clearing apoptotic debris and immune complexes, thereby reducing autoimmunity and systemic inflammation (Mitchell et al., 2002; Sun-Tan et al., 2010; Carlucci et al., 2016).