It should be a lipid and in other words a triglycerides however a sterol can also function as a hormone
The immune system is made up of a network of cells, tissues, and organs that work together to protect the body. One of the important cells involved are white blood cells, also called leukocytes, which come in two basic types that combine to seek out and destroy disease-causing organisms or substances.
The immune system works with organs and tissues to help you beat a disease or any other virus. Sometimes when a person's immune system is weak they usually die int he result of the virus or they usually end up in the hospital to get medication that helps their immune system.