American Airlines, Inc., operating as American Airlines (AA), is a U.S. airline and a subsidiary of AMR Corporation.t is headquartered in Fort Worth, Texas, adjacent to its largest hub at Dallas/Fort Worth International Airport. American Airlines operates an extensive international and domestic network, with scheduled flights throughout North America,â¦.
The major function of the immune system is to protect the host from environmental agents such as microbes or chemicals, thereby preserving the integrity of the body.
Immune system: A complex system that is responsible for distinguishing a person from everything foreign to him or her and for protecting his or her body against infections and foreign substances.