What different kinds of antigens are there? What role do they play in the human immune system?

Question

What will be an ideal response?

Answer 1

The human immune system is designed to protect us from exogenous (outside) and endogenous (inside) toxins, substances, particles, cells, and organisms that pose a threat to our physical well-being. These threats to our health are referred to as antigens. Antigens are the cast of bad characters that we want to keep out of our biological systems because they are disruptive and often dangerous. Exogenous antigens include bacteria, viruses like the cold virus that infected Nicole, fungi, and other entities that could potentially become life threatening, whereas endogenous antigens involve our body's own cells that are infected with viruses or have mutated into tumor or cancer cells. The immune system is like a nation's federal law enforcement agency (e.g., the FBI in the United States) protecting its citizens and government against endogenous threats and the national armed services (e.g., the army, navy, air force, and marines) protecting citizens from exogenous threats. The various agencies and branches of the military each have specialized roles, and collectively they serve to defend the body of the nation against threats to its survival.