C5 and diabetic kidney disease: Levels of C1q, MBL, Bb, C4d, C3a, C5a, and sC5b-9 were greater in subjects with biopsy-proven DKD; urinary MBL, Bb, C4d, C3a, C5a, and C5b-9 were increased in DKD with urinary C3a, C5a, and C5b-9 positively correlating with urinary protein and eGFR.