Host immunity

Question 1

What is innate response?

Answer 1

Functions in normal host WITHOUT prior exposure to invading microbes

Question 2

What is adaptive response?

Answer 2

• A response tailored to particular microbial infection and characterized by memory
• Consists of antibody response (humoral) and lymphocyte- mediated response (cell-mediated)
• Induced by exposure to a specific antigen, making the response specific; generating immunolgical response

Question 3

Difference between innate and adaptive

Answer 3

• Innate occurs faster
• Adaptive is highly specific
• Adaptive is more diverse in what it protects against
• Adaptive has a persistent memory that adapts to the invading pathogens
• Innate is better at self/nonself discrimination
• The soluble components of blood/tissue fluids of innate are antimicrobial peptides and proteins while adaptive uses antibodies.
• Major cell types of innate include various phagocytes, natural killer cells, and dendritic cells. Adaptive uses T and B cells, antigen presenting cells.

Question 4

What are constitutional factors?

Answer 4

• Factors that make one species innately susceptible and another resistant to certain infections
• Examples are genetics, age, metabolic factors, neuroendocrine factors, and environment

Question 5

What are the non-specific defenses associated with skin?

Answer 5

• Multilayered epipdermis and dermis (mechanical)

* High salts, organic acids, ß-defensins (chemical)

Question 6

What are the immunolgical defenses associated with mucous membranes?

Answer 6

1. Sticky mucus
2. Ciliary action
3. Lysozyme and anti-bacterial peptides
4. Cell sloughing/high turn over rate 5. Normal flora bacteria
5. Secretory IgA antibodies

Question 7

How does normal flora help with defense?

Answer 7

They compete for attachment sites and essential nutrients

Question 8

What are a few examples of mechanical defenses?

Answer 8

Flow of mucus, fluid, sloughing off of skin

Question 9

What are a few examples of chemical defenses?

Answer 9

Sebum, enzymes, lysozomes, acidity

Question 10

What are a few examples of microbiological defenses?

Answer 10

The normal flora throughout the body

Question 11

What is the main function of a type I interferon (IFN)?

Answer 11

Anti viral actions by:

• Inducing resistance to viral replication in all cells
• Increasing MHC class I expression and antigen presentation in all cells
• Activating NK cells to kill virus-infected cells

Question 12

What happens in a defective IFN system? An abrogated IFN system?

Answer 12

A defective IFN system leads to a reduced ability to contain infection, leading to increased chance of illness and death. Abrogation of the IFN system leads to global increase in susceptibility.

Question 13

What are the cell types involved with defense against microbes?

Answer 13

Phagocytic cells, lymphocytes, B cells, T cells, null cells/natural killer cells.

Question 14

What is phagocytosis?

Answer 14

• Engulfment and digestion of infectious agents or other foreign bodies.
• Phagocytes include macrophage & polymorphonuclear neutrophil

Question 15

How does the innate immune system distinguish self vs nonself?

Answer 15

• Pattern recognition receptors

* Toll like receptors (TLRs), Rig like receptors (RLRs), complement

Question 16

How does the adaptive immune system distinguish self vs nonself?

Answer 16

• Antigen presentation (MHCs)
• Antibodies
• T cell receptors

Question 17

What is the difference between oxygen dependent killings and oxygen independent killings?

Answer 17

Oxygen dependent killings involve reactive compounds such as H2O2 (hydrogen peroxide) and NO (nitric oxide). Oxygen independent killings involve enzymes like lysozyme.

Question 18

What is the primary function of neutrophils?

Answer 18

To phagocytize and kill extracellular bacteria and yeasts pathogens in acute inflammation.

Question 19

What is the primary function of eosinophils?

Answer 19

Plays a role in parasitic infections and patients with type I hypersensitivities. Very important in defense against helminths.

Question 20

What is the primary function of natural killer cells?

Answer 20

• Kills cells by releasing perforins and granzymes (which perforate membranes and trigger caspase), leading to mediated cell death.
• Important in viral infections

Question 21

How do natural killer cells recognize infected cells?

Answer 21

• Recognizes “altered self”. Two receptor required for discrimination: one to activate and one to block (if the cell is not infected).
• Virus infection associated ligand for activating.
• MHC I molecule for blocking.