Lecture 2 Pathogens/Innate immunity

Question 1

What is the overall function of the immune system?

Answer 1

• Kill pathogens
• Detect and kill abnormal cells
• Remove cell debris from the body

Question 2

Types of Pathogens

Answer 2

• Parasitic worms
• Fungi
• Protozoa
• Bacteria
• Viruses

Question 3

How do viruses work

Answer 3

• Hijack host cell
• Use replication and transcription processes to produce more viral DNA and capsid proteins
• viral self assembly and secretion from hijacked cell to infect neighboring cells

Question 4

What are your defenses against pathogens?

Answer 4

Innate Immunity
- Physical barriers
- rapid
- Non-specific
Adaptive Immunity
- Slower
- Specific
- Lymphocytes

Question 5

Components of the immune system

Answer 5

• Thymus
• Bone marrow
• Lymphatic vessels
• Tonsils –> lymphoid tissues
• Lymph nodes (monitors lymph)
• Spleen (monitors blood)
• Gut-associated lymphoid tissue (GALT)

Question 6

What role does Lymphatics play in the immune system?

Answer 6

• Return excess tissue fluid to the blood
• Transport pathogens/dendritic cells to lymph nodes
• Transport fat from digestive system to the blood

Question 7

What are elements of innate immunity?

Answer 7

1. Physical Barriers
2. Phagocytes
3. Natural Killer (NK) Cells
4. Antimicrobial proteins
5. Inflammation
6. Fever

Question 8

What are the physical barriers in innate immunity

Answer 8

• Epithelium: skin and mucous membrane
• Glandular Secretions: Mucous, antibodies, enzymes which trap pathogens
• Stomach Acidity: low pH of stomach acid
• Mechanical Removal: mucociliary escalators, tears, coughing, sneezing and GI motility

Question 9

Describe phagocytes within innate immunity

Answer 9

• Consists of Neutrophils (most common), macrophages, and dendritic cells
• Pathogens taken up via TLRs or Fc Receptors
• Antibody coating is called opsonization
• Macrophages and dendritic cells display antigen fragments to interact with lymphocytes

Question 10

How do Natural Killer (NK) cells work?

Answer 10

• Inhibited by cells expressing MHC1
• If no MHC1 expression, NK cells release cytotoxic cytokines which kill target cells

Question 11

How do Antimicrobial Proteins work?

Answer 11

• INFalpha and beta prevent viral replication in cells
• INFgamma activate macrophages and other immune cells
• Complement system destroys target cell membranes through MAC (membrane attack complex)

Question 12

How does Inflammation work?

Answer 12

• Swelling, redness, heat and pain
• Slow spread of pathogens
• Mobilization of local, regional, and systemic defenses
• Causes chemical change in interstitial fluid and releases histamine and heparin
• Vasodilation occurs and pain receptors are stimulated

Question 13

How does a fever work?

Answer 13

• Pyrogens (bacterial components and IL-1) change the thermoregulatory set point in the hypothalamus (increasing above 37.2 degrees)
• Speeds up metabolic activity in host
• Inhibits some pathogens