C3 and pancreatic insulinoma: IL-1β also up-regulated C3 gene expression levels in rat insulinoma cell line INS-1 832/13 (Fig. 1C), used as a model of β-cell function, and similarly to human pancreatic islets (16), IL-1β triggered INS-1 C3 secretion and enhanced generation of intracellular C3 protein found within lysates, which was undetectable in C3-KO INS-1 cells (Fig. 1D).