C4A and systemic lupus erythematosus: Regarding the association between SLE and C autoantibodies, some authors have found that anti-Sm, anti-DNA and anti-SSA are related to C3, C4 and/or C3a (13, 21, 22), while others have described a lack of association between anti-RNP autoantibodies and C3 and C4 (23).