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 humans body.Innate, or nonspecific, immunity, is functioned by
the skin, tears, mucus, and saliva.

These barriers
protect the body from a diseases 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
persons immune system becomes activated and
generates a response or by a vaccination.

immunization is controlled by a persons 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 infections or other factors.

factors such as stress and poor nutrition can also
weaken the immune system.