The Immune System

The immune system is a group of cells and organs

that defend the body against invaders causing

disease. The immune system is made up of mostly

white blood cells and their contact with lymph

nodes, spleen, tonsils, intestines, and lungs. The

immune system rejects and attacks any substances

not normally present within the human's body.

Innate, or nonspecific, immunity, is functioned by

the skin, tears, mucus, and saliva. These barriers

protect the body from a disease's entrance, but do

not prevent it. Adaptive, or specific, immunity

processes when invaders actually attack the body.

In adaptive immunity, proteins called antibodies

appear in body fluids to fight bacteria and toxins,

while other cells in adaptive immunity resist a

virus' reproduction within cells. Resistance called

immunity is reached by active or passive

immunization. Active immunization occurs when a

person's immune system becomes activated and

generates a response or by a vaccination. Natural

immunization is controlled by a person's immune

system, while a vaccination is a chemically-created

weakened form of the disease unable to cause

harm. Passive immunization is when a person

receives only temporary immunization by the use

of antibodies. Disorders of the immune system

range widely. Deficiencies within the immune

system may be acquired or inherited. Acquired

disorders, such as HIV and AIDS, can be caused

by