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 Response

Specific Defense Immune response: Pathogen, or antigen, gets past nonspecific defense Lymphocytes 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 immunity Antibody 1. Antigen recognized by specific B cell 2. B cells produce large #’s of plasma B and memory B cells 3. Plasma B cells release antibodies 4. Antibodies bind to antigen 5. 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