C4B and kidney disorder: Indeed, deposition of complement activation products is a feature of both diabetes-related retinopathy (30) and nephropathy (31), although there is also evidence for lectin and classical pathway involvement; serum MBL levels are a strong biomarker for diabetic nephropathy in both T1D and T2D, and C4b as well as C1q were found deposited in human kidney samples from diabetic patients, correlating with nephropathy (32).