In order to further investigate the correlation of the complement cascade with DKD-stage inflammation and fibrosis, a set of 43 tissue sections of human kidney DKD tissues (class I–IV) were analyzed using immunofluorescence for the expression of C3, C1q, C4, and IGM proteins (immunofluorescence results and demographic characteristics of the patients are shown in Table S4). Here, C4A is linked to diabetic kidney disease.