A positive regulator of the alternate pathway (AP) of complement (PubMed:20382442, PubMed:28264884). It binds to and stabilizes the C3- and C5-convertase enzyme complexes (PubMed:20382442, PubMed:28264884). Inhibits CFI-CFH mediated degradation of Complement C3 beta chain (C3b) (PubMed:31507604).