What is a group of proteins that normally circulate in the blood in an inactive form and activated by contact with nonspecific antigens such as foreign blood cells or bacteria is known as?

A group of proteins that circulates in the blood in an inactive form and is activated by contact with nonspecific antigens, such as foreign blood cells or bacteria, is known as the complement system. This system plays a crucial role in the immune response by helping to clear pathogens and promote inflammation. Once activated, complement proteins can enhance opsonization, facilitate phagocytosis, and contribute to the lysis of pathogens.