The Immune system 40-1

40-2T cell attacking cancer cell

Virus with anti-Bodies attached

virus

bacteria

virus

Purpose

• To fight infection by producing cells that inactivate foreign substances.

• Nonspecific defenses: act like a fortress wall• Specific defenses: act like security guards

Nonspecific defenses: 1st line of defense• Skin: the first line of

defense. Layers of dead cells make a barrier.

• Oil and sweat glands: make an acid environment that kills bacteria.

• Mouth, nose, eyes: mucus, saliva and tears have enzymes that destroy bacteria entering.

• Nose hairs trap bacteria.

2nd line of defense: Inflammatory response

• A non-specific reaction to tissue damage or infection.

• Increased white blood cells- engulf bacteria.

• Fever: higher body temp. slows growth of pathogens.

• Interferon: proteins that disrupt viral replication.

Phagocyte eating a parasite

Hepatitis C and interferon

fever

Specific defenses: the immune response

• Triggered by an antigen (viruses, bacteria, etc.)

• Plasma cells release antibodies: proteins shaped like a ‘Y that bind to the antigen and prevent it from infecting cells.

• B cells provide immunity against invaders in the bodily fluids.

• Memory B cells prevent a future infection: Humoral immunity

Cell mediated immunity • A body can defend

itself against its own cells if they become infected or cancerous.

• T cells killer T cells• The killer T cells will

destroy the infected cells.

• Memory T cells will respond if the antigen returns. Killer T cells attacking a cancer cell

Organ transplants • Our cells recognize

another person’s cells as foreign, and attack them.

• Organ recipients must take drugs that suppress their I.S. to avoid organ rejection for the rest of their lives.

Active immunity

• Vaccinations introduce a weakened or dead pathogen into the body.

• Without getting sick, the body makes antibodies, arming the immune system.

• If you are exposed later, you will not get sick.

Flu shot

Passive immunity

• A mother’s antibodies transfer to her child in utero and with her breast milk, giving her baby protection against diseases.

Immune system disorders 40-3

Pollen, rheumatoid arthritis,dust mite, HIV, asthma

Allergies

• An overreaction of the immune system

• Allergens (pollen, dust, mold) attach to mast cells, which release histamines.

• Body response: sneezing, excess mucus, itching

• Meds: antihistamines

Asthma

• An allergic reaction that causes a chronic respiratory disease.

• Smooth muscles that line the airways contract, thick mucus clogs the smaller passageways

• #1 cause of serious illness in children.• No cure, but treatments are available.

Autoimmune diseases• Happens when the I.S.

attacks a body’s own cells by mistake.

• Type I diabetes: antibodies attack insulin-producing cells of the pancreas.

• Multiple sclerosis: antibodies destroy the myelin sheath of neurons in the brain and spine.

AIDS, an immunodeficiency disease

• Caused by Human Immunodeficiency Virus.• It attacks and destroys cells of the immune system itself

(helper T cells).• The body’s defenses against any disease are eventually

destroyed, and the person will die from AIDS.

T cell (green) with HIV viruses

HIV

• HIV virus is capable of mutating. • Multiple drug resistant strains develop as the

virus evolves.

Maintaining health

• Eat a healthful diet.• Get regular exercise

and enough rest.• Abstain from harmful

activities.• Get regular medical

and dental check-ups.

Review

1. The purpose of the immune system is…..

2. Some diseases of the immune system are…………..

3. We can prevent disease by………