1. Defense Against Infectious Disease

2. Review Disease- a disruption of homeostasis
Infectious disease- caused by a pathogen
Pathogen- disease producing organism such as bacteria, viruses, fungi, protozoan

3. Innate immunity- non specific immunity
Skin and body secretions
Inflammation response
Phagocytes
Neutrophils
Monocytes
Macrophages (monocytes that have migrated into tissue
Eosinophils
Interferons- proteins that protect against viruses

4. Both activated by antigens: foreign proteins
Acquired immunity- building up an immune response to a specific pathogen
2 types of responses: Both involve lymphocytes which circulate in blood and lymphatic system
1. Production of antibodies, called antibody or humoral immunity.
2. cellular, or cell mediated, immunity
Both activated by antigens: foreign proteins

6. Lymphatic system-
Collects tissue fluid and filters it through the lymph nodes and thymus
Lymph nodes- help filter out and concentrate pathogens. Dense with lymphocytes

7. Antibody, aka Humoral, Immunity
Macrophages eat bacteria- antigens are presented on surface
Helper T cells bind to macrophage and is “activated.” Signals B cell lymphocyte to react and change into a plasma cell- a plasma cell makes antibodies
Antibodies mark bacteria or other cells for death
Some B cells turn into Memory B cells

8. Cell-mediated immunity
Macrophage eats bacteria, presents antigen on cell surface. Helper T cell binds to macrophage- is “activated”
Helper T cell stimulates another type of lymphocyte- Killer T cell (aka cytotoxic T cell)
Killer T cells multiply and attack the pathogen directly- inject enzyme Perforin into bacteria or cell, which kills them.
Release cytokines- signals rest of immune system to activate

9. Passive vs Active immunity
Passive: Mother’s milk, placental transfer or plasma infusion
Active- patient injected with a vaccine. A weakened, dead or incomplete portion of pathogen is injected, stimulating an antibody response
History: first safe vaccine 1798 by Edward Jenner

10. HIV
Human immunodeficiency virus
Spread by direct contact of body fluids or blood
Destroys Helper T cells
It may take 8-10 years for symptoms to appear

11. What role do phagocytes play in defending the body against disease?
What role does a lymph node play in defending your body against microorganisms?
What is the difference between naturally acquired passive immunity and naturally acquired active immunity?