Immune System

• The body’s primary defense against disease causing pathogens that threaten our homeostasis.

• Can be identified by molecules on their outer surface (antigens)

Antigens• Found on both viruses and

bacteria • Trigger an immune response.• Recognized by body as

invaders.• White blood cells and

antibodies attack.• The body can usually take

care of a virus but antibiotics are often needed to kill bacteria.

White Blood Cell

• Some are specialized to engulf invading pathogens.

• Others produce antibodies – proteins that either attack or mark for killing.

• WBC’s have large nuclei.

• Most antibodies and WBC’s break down soon after having defended the body.

• But some specialized WBC’s remain. These can produce antibodies to fight off later invasions of the same microbes.

• This gives us immunity to viruses such as chicken pox, mumps and measles years later.

Vaccinations• Scientists have discovered that weakened microbes

stimulate the immune system to produce antibodies without making the person sick.

• Vaccines are made from weakened killed or parts of pathogens and injected into the body.

Damage to the Immune System

• Stress and fatigue can lower resistance and open the door to infection by pathogens.

• AIDS weakens the immune system and may leave a person unable to deal with infections and cancer cells.

• People with AIDS often die from secondary infections.

Problems Associated With Immune Response

• Allergies – Your bodies may react to things like foods, insect bites, dust or pollen and produce an immune response.

• The body reacts by releasing histamines which produce an inflammatory response.

• Transplanted organs – body detects foreign proteins. Tries to rid body of invader. This is organ transplant rejection.

• Doctor gives immune system suppressing drugs.