C3 and systemic lupus erythematosus: And, the level of anti-dsDNA in SLE patients was found to negatively correlate with the level of C3 (r = −0.4244, P = 0.006) (Supplement Fig 1A) and C4 (r = −0.3905, P = 0.012) (Supplement Fig 1B) and positively correlate with SLEDAI (r = 0.3575, P = 0.024) (Supplement Fig 1C).