Innate Immunity MLS 227T

What are the Two types of Defense Systems functions and Examples?

* Definition not from notes

1. External Defense System - Anatomical (physical, chemical and biological) barriers that keep microorganisms from entering the body

   • Epidermis and Dermis - 3-5pH

   • Mucus - 5 pH - physical barrier, block bacteria from adhering to epithelial cells

   • Respiratory tract

     • Celia - clear deposited material

     • coughing + sneezing removed pathogens

   • Digestive Tract - HCl keeps low pH (1) - prohibit pathogen growth

   • Hair - physical barrier + sensory detection * releases antimicrobial substances (sebum) to trap pathogens

   • Tears + Saliva - lysozyme attacks cell walls of G+ bacteria

2. Internal Defense System - Cells (and soluble factors) that defend against foreign invaders

   • Pattern-Recognition Receptors (PRRs) - found on Innate + Adaptive immune cells - recognize molecules unique to organisms called pathogen-associated molecular patterns (PAMPS) - activate phagocytic cells

   • Acute-Phase Reactants (APRs) - Soluble, found in serem, increase in response to infection, injury, or tissue trauma, facilitate contact b/t microbes and phagocytic cells

   • Inflammation - PRISH (Pain; Redness; (Immobility), Swelling, Heat

   • Phagocytic Cells

   • NK Cells

   • Innate Lymphoid Cells

Process of Inflammation

Simplified:

1. Vasodilation

2. Rolling leukocytes

3. Endothelial cell binding

4. Diapedesis

5. Chemotaxis

(In Depth)

1. Macrophages and mast cells at the site of infection release chemokines that cause vasodilation and induce selectins

2. Selectins loosely bind circulating leukocytes and cause them to roll along vascular wall

3. Chemokine-induced integrins on the leukocytes bind firmly to the endothelial cells

4. Integrins enable leukocytes to crawl between endothelial cells (diapedesis)

5. Leukocytes follow chemokine concentration gradient to the site of infection (chemotaxis)

Process of Phagocytosis

Simplified:

1. Adherence

2. Engulfment

3. Formation of Phagosome

4. Granule Contact

5. Formation of Phagolysosome

6. Digestion of Microorganism

7. Excretion

(In Depth)

1. Physical contact b/t phagocytic cell and microorganism - aided by opsonins

2. Cytoplasm surrounds microorganism

3. Membrane surrounds cytoplasm surrounding microorganism

4. Lysosomal granules contact and fuse phagosome

5. Contents of lysosome empties into membrane bound space of phagosome

6. Microorganism is digested by hydrolytic enzymes

7. Contents of phagolysosomes are expelled thru exocytosis

Examples of Acute Phase Reactants +_Function

1. C-Reactive Protein - Opsonization + Compiment Activation

2. Fibrogen- Clot formation

3. Compliment C3 - Opsonization + Lysis