Human Immunity

Ch. 40

I. Infectious DiseaseA. Disease

1. Any change (other than injury) that disrupts normal body function

2. Caused by pathogens

B. Pathogens1. Disease causing agent such as bacteria, virus,

protist, worm or fungi

C. Germ Theory of Disease1. For thousands of years, humans believed sickness

was caused by curses, evil spirits or angry gods2. “Germ Theory of Disease”- Louis Pasteur and

Robert Koch observed that infectious diseases are caused by microorganisms

150 km/hr sneeze!

D. How Diseases are Spread1. Physical contact

a. Direct – touching an infected personb. Indirect – through the air or on objects

2. Contaminated Food or Watera. Be sure to cook food thoroughly and sanitize

water3. Infected Animals

a. Vectors – animals that transmit disease to humans

Ex: malaria from mosquito or bubonic plague from fleas

E. Fighting Infectious Diseases1. Wash your hands frequently2. Drugs specific to pathogen (ex: penicillin)3. Rest, plenty of fluids, good nutrition4. Your immune system!

White Blood Cell

II. Immune SystemA. What is immunity?

1. The ability of the body to resist pathogens

2. Function of immune system is to fight infection through the production of cells that inactivate foreign substances

B. Human immune system includes two general categories against infection:

1. Non-specific defenses2. Specific defenses

III. Nonspecific ImmunityA. First Line of Defense

1. Skin – how?2. Mucus membranes, saliva and tears have

antimicrobial proteins (lysozymes) that break down the cell wall of bacteria

3. Oil and sweat glands create an acidic environment that slows the growth of bacteria

4. Digestive and respiratory systems - how?

B. Second Line of Defense (once infected)1. Inflammation - how?2. Fever - how? 3. White blood cells (phagocytes) engulf

foreign particles4. Interferons - proteins that interfere with

viral replication

Skin Wound

Bacteria enter the wound

Phagocytes move into the area and engulf the bacteria and cell debris

Capillary

The Inflammatory The Inflammatory ResponseResponse

(DRAW FIG. 40-7 PG. (DRAW FIG. 40-7 PG. 1037)1037)

IV. Specific Immunity A. When a pathogen gets past the body’s non-

specific defense, a specific Immune response is triggered

1. Targets specific individual invaders2. You are born with this system3. You are able to recognize millions of invaders

B. Antigen is any substance that triggers an immune response

1. Recognized by two types of lymphocytes (white blood cells) called B cells and T cells

2. B cells provide immunity against antigens and pathogens in body fluid

3. T cells provides defense against abnormal cells and pathogens in living cells

C. Humoral Immunity (body fluids)1. When B cells recognize a pathogen, large

numbers of plasma cells and memory B cells are produced

2. Plasma cells release antibodies to attack the pathogena. Antibodies = “Y”-shaped proteins that recognize

and bind to antigens, helps to destroy specific pathogens

3. Once exposed to a pathogen, millions of memory B cells remain, thus reducing the likelihood of a 2nd infection

DRAW Figure 40-8, pg 1038

Antigen-binding

sites

Antigen Antibody

Humoral Immunity (DRAW FIG. 40-9, 1039)

Humoral Immunity Movie

D. Cell Mediated Immunity 1. Body’s primary defense against cells that are

cancerous or infected by viruses. Also important in fighting infection caused by fungi and protists.

2. Begins with a wandering macrophage (WBC) engulfing a foreign particle (the antigen).

3. The antigen is broken down and pieces of the surface proteins of the pathogen are moved to the surface of the macrophage

4. This is done by the HLA protein. It is unique to each person and displays both self and non-self antigen fragments

5. Only T-cells that have receptors that fit to the presented antigens bind to the macrophage.

6. Binding of the T cells with the macrophage stimulates these specific T-cells to divide many times forming many different kinds of T-cells.

7. Helper T cells (activated by binding to macrophage) stimulates the production of memory T cells and killer T cells

8. Memory T cells (like memory B cells) will “remember” the antigen and cause a secondary response if seen again

9. Killer T cells then track down and kill any substance with those antigens (pathogen or body cell)

Macrophage

T Cell

Helper T Cell

Killer T Cell

Infected CellAntigens are displayed on

surface of macrophage

T cell binds to activated macrophage

T cell, activated by macrophage, becomes a helper T cell

Helper T cell activates killer T cells and B cells

DRAW FIG 40-10, pg. 1040

Killer T cells bind to infected cells, disrupting their cell membranes and destroying them

E. Transplants1. In transplant patients, T-cells recognize foreign

markers on the cell surface of the transplanted organ and try to kill the cells.

2. This is organ rejection

V. Acquired Immunity A. Active Immunity - body makes its own

antibodies in response to an antigen1. Vaccine

a. Take a virus or other pathogen and destroy or weaken its nucleic acid.

Why do we want to do this?b. You can alter the DNA of the pathogen by

using chemicals, radiation or growing it in a different host.

Why are you asked if you are allergic to eggs before you get a flu shot?

c. Leave the protein coat undamaged. Why?

d. Inject this mixture (the vaccine) into humans or other animals.

e. Your body responds as if you had the disease and you form memory cells for this disease. Why don’t you get this disease?

f. Next time host is exposed to the pathogen, the body will recognize and destroy pathogen before the disease affects the body. Why can you fight it off so fast?

B. Passive Immunity - antibodies produced by another animal are used by another organism1.Mother passes antibodies on to fetus/baby2.Antibodies are injected into travelers to protect

them from tropical diseases such as malaria

VI.Immune System DisordersA. Allergies – overreaction to antigens called allergens

(dust, mold, pollen and bee stings, etc)1. Causes release of histamines

a. Increase blood flow and fluids to surrounding area

b. Increased mucus production, sneezing and inflammation

2. Anaphylactic shock – severe allergic reaction that involves one of more body systemsa. Inflammation of respiratory systemb. Drop in blood pressure (starves the brain of O2)

c. Can result in death

B. Asthma – chronic respiratory disease1. Triggered by allergens, stress, exercise, smoke,

etc.2. Narrowing of air passages causes wheezing,

coughing and difficulty breathing3. No cure, but medications can control symptoms

C. Autoimmune diseases – immune system mistakenly attacks the body’s own cells1. Includes Type I diabetes, rheumatoid arthritis,

myasthenia gravis, and multiple sclerosisD. AIDS (Acquired Immune Deficiency Syndrome)

1. Caused by the human immunodeficiency virus (HIV)a. Exists in blood and body fluidsb. Retrovirus (RNA) that evades the defenses of the

immune system and attacks helper T cellsc. Leaves the body without protection from

pathogens

Cell Beach Movie

2. The lower the T cell count, the more advanced the disease

3. AIDS does not directly kill patient, secondary infection does (pneumonia most common)

4. Transmission of HIVa. Sexual activity (intercourse and oral)b. Sharing needlesc. Blood contactd. Infected mother during pregnancy, birth,

or breast-feeding

HIV Movie

5. AIDS Treatmenta. No cureb. Drugs to suppress the virus (drug

“cocktails”, AZT)