The protein, made naturally in humans, is present mostly in fetal liver and kidney tissue, leading to the conjecture that it serves as a growth inhibitor in early development.

• 人体本身会制造这种蛋白，但多数出现在胎儿的肝及肾组织，因此引起猜测：该蛋白是早期发育阶段的生长抑制因子。