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.
The immune system is the body's way of protecting itself against disease. It is made up of a complex recognition and response system to bacteria or other pathogenic (disease-causing) organisms. Specific antibodies to these organisms enhance the effectiveness of the body's defenses against these bacteria.