Immune System

Our defense system against

the little guys.

Disease

Any change, other than injury, that disrupts normal body functions

Can be caused by agents or pathogens, environmentally, or are inherited

What are some examples of pathogens?

Pathogens Viruses Bacteria Protists Parasites (worms) Fungi

Diseases Spread

Physical contact Direct contact with bodily fluids Indirect through air from coughing or

sneezing or touching contaminated objects

Contaminated Food and Water Infected Animals

Vectors: animals that carry pathogens Example: Lyme disease and the deer tick

Immune System

Functions to fight infections through the production of cells that inactivate foreign substances or cells = immunity

Body fights infection:

1. Nonspecific Defense

2. Specific Defense

Nonspecific Defense

First line of Defense: Keep pathogens out of body. Prevent infection. Skin, mucus, sweat, tears,

stomach acid. Second line of Defense:

Inflammatory response Mast cells release Histamines. WBC’s, phagocytes, drawn in. Fever (kills microorganisms) Swelling, redness Pus

Skin Wound

Bacteria enter the wound

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

Capillary

The Inflammatory ResponseThe Inflammatory Response

Specific Defense

Immune response:Pathogen, or antigen, gets past

nonspecific defenseLymphocytes recognize specific

antigens: B cells - humoral immunity T cells - cell-mediated immunity

Macrophages: bring antigens to the T-cells from the pathogen they ingest.

Humoral Immunity

Antibody mediated immunity1. Antigen recognized by specific B cell2. B cells produce large #’s of plasma B

and memory B cells3. Plasma B cells release antibodies4. Antibodies bind to antigen5. Memory B cells prevent another

infection.6. Takes place in the fluids (humors).

Antigen-binding

sites

Antigen Antibody

Structure of an Antibody

Antibodies:

Proteins that

recognize & bind to specific antigens.

Cell-Mediated Immunity

Once the pathogen is inside cell:

1. Cell signals infection to Helper T cell.

2. Helper T cell can activate BOTH Killer T cells and Plasma B cells

3. Killer T cells kill infected body cells.

4. Memory T cells are produced after exposure.

Acquired Immunity

Active Immunity: Body’s produces antibodies to an antigen. Vaccination = injection of weakened or

mild form of pathogen causes antibody production

Passive Immunity: Antibodies produced by another organism

injected into bloodstream Lasts short time Antibodies from mom or mother’s milk.

What happens when things go wrong?

Allergies

Allergies are the “overreaction” of the bodies immune system to microorganisms, like pollen or animal dander.

The bodies mast cells release histamines, because of the increase of blood and fluids to the area, we experience a runny nose and watery eyes.

Allergies can be either genetic or environmentally caused.

Asthma

Narrowing of the air passages by the spasm contractions of the smooth muscle.

Chronic disease Reaction to antigens

or stress related. Both hereditary and

environmental causes.

Autoimmune disorders

Autoimmune disorders are when the body attacks itself.

It has lost the ability to recognize its own cells. No sense of “self”.

Diseases like Type I Diabetes, Rheumatoid arthritis, Lupus and Multiple sclerosis (MS) are common autoimmune disorders.

Lupus rash

RA

Koch’s Postulates

The pathogen should always be found in the body of a sick organism and should not be found in a healthy one.

The pathogen must be isolated and grown in the laboratory in a pure culture.

When purified pathogens are placed in a new host, they should cause the same disease that infected the host.

The very same pathogen should be re-isolated from the second host. And it should be the same as the original pathogen