Isolation from Fetal Bovine Serum of a Fragment b of Complement Factor B-like Protein Improving a Long-Term Survival of Human Endothelial Cells

It is known that serum is a most important factor supporting cell survival and growth. Particularly, the deprivation of serum would result in the death of human endothelial cell. Our previous paper reported an endothelial cell-viability maintaining factor (EC-VMFa) purified from fetal bovine serum and identified as an apolipoprotein. In the present further study, it is demonstrated that another potent serum factor (refer as EC-VMFb) is also possessed of the endothelial cell-viability maintaining activity, improving a long-term survival of human endothelial cells in serum-free medium. EC-VMFb has a molecular weight of 66,000 (reduced and nonreduced), pIof 4.5 and has been identified as fragment b of complement factor B (Bb)-like protein by amino-terminal amino acid sequence.