Immune System

Disease• Any change in the body not due to

injury that disrupts homeostasis

• Pathogens = Sickness makers

How do we know pathogens make you sick?

Koch’s Postulates

1. The suspected causal organism must be constantly associated with the disease.

2. The suspected causal organism must be isolated from an infected organism and grown in pure culture.

3. When a healthy susceptible host is inoculated with the pathogen from pure culture, symptoms of the original disease must develop.

4. The same pathogen must be re-isolated from the organism infected under experimental conditions.

Lyme Disease Risk

Lyme Disease Etiology• Allen Steere (1975) Yale University

• 39 children from Lyme Connecticut

• All had pain and joint inflammation

• All had insect bites and rashes

• Dr. Willy Burgdorfer found spirochete in ticks

• Steere found same bacterium in his patients

Non-Specific Immunity1st Line of Defense• Skin• Mucous membranes• Saliva• Mucus• Nasal hair• Tracheal cilia• Stomach acid• Sweat• Tears

Non-Specific Immunity

2nd Line of Defense• Phagocytes• Natural killer (NK) cells• Inflammatory response• Pyrogens (Reset thermostat in hypothalamus)• Complement proteins• Interferon (Prevents viral replication)• Lysozyme (Pokes holes in bacterial cell walls)

Non-Specific Immunity

• Complements identify antigen

• Granulocytes attack antigen creating pus

• Macrophages perform phagocytosis on bacteria

Inflammatory Response1. Damaged tissue releases histamine

2. Capillaries become “leaky”

3. Blood flow increases to area

4. Clotting factors and phagocytes released into the wound

5. Phagocytes engulf bacteria, cellular debris, & dead cells

6. Macrophages release cytokines which attract immune system cells

7. Platelets seal the wound with a clot

Specific Defenses

• Humoral immunity – immunity against pathogens in body fluids (blood and lymph)

• Immune response carried out by lymphocytes

• Cell-Mediated immunity – Antibody production

Antibodies• Antibody = a protein that helps to

destroy pathogens

• Substrate specific

• Cause agglutination which attracts phagocytes

• Made by plasma cells

• Plasma cells made by b-lymphocytes

Humoral Immunity

IgM

IgAIgG

Antibodies

Cell Mediated Immunity

• Active immunity - vaccination with antigen (lasts for years)

• Passive immunity – transferring antibodies from one person to another (lasts several weeks)

Dr. Edward Jenner