C4A and systemic lupus erythematosus: Most complement-related SLE defects are found in the C1 (C1QA, C1QB, C1QC, C1R, C1S) (Lood et al., 2009; Bienaime et al., 2010; Demirkaya et al., 2017; Almlof et al., 2019) or C4 (C4A, C4B) compartments (Blanchong et al., 2001; Vinuesa et al., 2023).