Functional network analysis in the study showed that the gene expression of C1qa, C1qb, C1qc, C1r, and C2, the complement components of the classical pathway, were significantly increased, and the expression of Cd59, the major cell surface inhibitor of C5b-9 formation, was significantly decreased in the BPH tissue of the BPH rat model compared to their normal prostate tissue9. Here, C2 is linked to benign prostatic hyperplasia.