Innate Immunity

Question 1

What are some exterior physical and chemical defenses

Answer 1

• Lysozyme in tears and other secretions
  -commensals
• removal of particles by the rapid passage of air over turbinate bones
• Bronchi (mucus and cilia)
  -Gut (acid, rapid ph change, commensals)
  -flushing of the urinary tract
  -low ph and commensals of the vagina
  -skin (physical barrier, fatty acids, commensals)

Question 2

What do lysosomes do to bacteria

Answer 2

-They digest the cell wall of gram + and gram -ve bacteria
- cleaves B-(1-4) linkages between sugar molecules.

Question 3

What are the mechanical, chemical, and microbiological defenses against infection found in skin

Answer 3

-Mechanical
epithelial cells joined by tight junctions
the longitudinal flow of air or fluid
-Chemical
Fatty acids
B- defensins lamellar bodies cathelicidin
-Microbiological
normal microbiota

Question 4

What are the mechanical, chemical, and microbiological defenses against infection found Gut

Answer 4

-Mechanical
Epithelial cells joined by tight junctions
The longitudinal flow of air or fluid
-Chemical
Low pH
Enzymes (pepsin)
a-defensins (cryptdins)
Regll (lecticidins)
cathelicidin
-Microbiological
normal microbiota

Question 5

What are the mechanical, chemical, and microbiological defenses against infection found Lungs

Answer 5

-Mechanical
Epithelial cells joined by tight junctions
movement of mucus by cilia
-Chemical
Pulmonary surfactant
a-defensins cathelicidin
-Microbiological
normal microbiota

Question 6

What are the mechanical, chemical, and microbiological defenses against infection found Eyes/nose/oral cavity

Answer 6

-Mechanical
epithelial cells joined by tight junctions
Tears nasal cilia
-Chemical
enzymes in tears and saliva (lysozyme)
histatins b-defensins
-Microbiological
normal microbiota

Question 7

What cells in the intestine produce antimicrobial proteins and which ones are produced?

Answer 7

The paneth cells found in epithelial crypts
they produce a-defensins (cryptdins) and the antimicrobial lectin RegIII

Question 8

What are a-defensins?

Answer 8

amphipathic peptides that disrupt the cell membranes of microbes by inserting into the lipid bilayer. This leads to the formation of pores in the membrane and thus the membrane loses its integrity and collapses, leading to the death of the microbe.

Question 9

What is the anti-microbial defensins, RegIIIy?

Answer 9

It is a C-type lectin that binds to peptidoglycans on bacterial cell walls. It mostly kills gram-positive bacteria

Question 10

What results in the development of inflammatory bowel diseases (IBD)?

Answer 10

The immune system reacts with potentially pathogenic microbes while at the same time remaining ignorant of the non-pathogenic microbiota. The disruption of this delicate balance results in the development of IBD

Question 11

What happens when there are not enough commensal “friendly” bacteria in the gut lumen?

Answer 11

-The colon contains lots of commensals
- Antibiotics kill many of the commensal bacteria
- Pathogenic bacteria increase in number in that area and produce toxins that cause mucosal injury
- Red and white blood cells leak into the gut between injured epithelial cells

Question 12

What are the primary and secondary lymphoid organs and what do they produce?

Answer 12

1. Primary lymphoid organs
   - Bone marrow- produces white blood cells
   - Thymus- helps with T cell development
2. Secondary lymphoid organs
   -lymph nodes

Question 13

Give examples of lymphocytes and their soluble mediators.

Answer 13

1. B cell- antibodies
2. T cell- cytokines
3. Large granular lymphocyte- cytokines

Question 14

Give an example of phagocytes and their soluble mediators?

Answer 14

1. monoclear phagocyte- cytokines and complements
2. neutrophil
3. eosinophil

Question 15

Give an example of auxiliary cells and their soluble mediators?

Answer 15

1. basophil- inflammatory mediators
2. mast cells- inflammatory mediators
3. platelets- inflammatory mediators

Question 16

what are the soluble mediators for tissue cells?

Answer 16

1. interferons
2. cytokines

Question 17

what are the four Latin words that describe inflammation?

Answer 17

calor= heat
dolor=pain
rubor=redness
tumor=swelling

Question 18

what causes the effects of inflammation?

Answer 18

The effects are all due to the action of local cytokines made by white blood cells in the infected tissue (such as after a splinter in the finger) which affects the local blood vessels.

Question 19

What happens when an infection triggers an inflammatory response?

Answer 19

• bacteria trigger macrophages to release cytokines and chemokines
• vasodilation and increased vascular permeability cause redness, heat, and swelling
• inflammatory cells migrate into the tissue, releasing inflammatory mediators

Question 20

What process do white blood cells use to migrate into a tissue?

Answer 20

extravasation

Question 21

describe phagocytosis?

Answer 21

-phagocytes arrive at a site of inflammation by chemotaxis. The infectious agent is then taken into the phagosome by pseudopodia extending around it.
- once inside, the lysosomes fuse with the phagosome to form a phagolysosome and the pathogen is killed. Some antigenic peptides will then be displayed on the membrane cell surface in the groove of an MHC Class II molecule.

Question 22

What are the three types of antigen-presenting cells?

Answer 22

1. Dendritic cells
2. Macrophages
3. B lymphocytes

Question 23

What do macrophages and DC cells express?

Answer 23

receptors for many antigenic structures found on a range of pathogens

Question 24

What do mannose, glucan, and scavenger receptors bind?

Answer 24

Cell wall carbohydrates of bacteria, yeast, and fungi

Question 25

What Toll-like receptors (TLRS) do?

Answer 25

TLRS can recognize if a bacterium is gram-positive (such as the TLR-1: TLR-2 dimer) or gram-negative bacteria (TLR-4 sees LPS)

Question 26

What do NOD-like receptors do?

Answer 26

sense bacteria that have invaded the inside of the cell so are found in the cytoplasm

Question 27

How do dendritic cells initiate the adaptive immune response?

Answer 27

They do this by taking up antigens in infected tissues such as the skin and then moving to a local lymph node to activate resting T helper cells ( naive T cells that have never seen antigen)

Question 28

Describe opsonisation?

Answer 28

- Bacteria is coated with complement and IgG antibody - When C3b binds to CR1 and the antibody binds to the FC receptor, bacteria are phagocytosed - Macrophage membranes fuse, creating a membrane-enclosed vesicle, the phagosome - Lysosomes fuse with these vesicles, delivering enzymes that degrade the bacterium

Question 29

What does the binding to Fc receptors and complement receptors do?

Answer 29

It signals the fusion of lysosomes (filled with enzymes) with phagosomes and increases bactericidal activity.

Question 30

What are the escape strategies some bacterial species have to counter macrophage activity against them? (6)

Answer 30

1. Toxin release organism releases toxins that kill phagocyte e.g. staphylococci, streptococci, amebae 2. Opsonization prevented organism (e.g. staphylococci) produces a protein (e.g protein A) which prevents interaction between opsonizing antibody and phagocyte, so preventing phagocytosis 3. Contact with phagocytes prevented the organism possesses a capsule that prevents contact with the phagocyte, e.g. Streptococcus pneumoniae, Haemophilus, bacillus anthracis 4. Phagolysosome fusion inhibited Fusion of phagosome and lysosome inhibited by the organism, e.g. mycobacterium tuberculosis, toxoplasma, chlamydia 5. Escape into the cytoplasm organism escapes from the phagolysosome into the cytoplasm and replicates within the phagocyte, e.g leishmania T.cruzi 6. Resistance to killing organism resists killing by producing antioxidants, e.g by catalase in staphylococci, or by scavenging free radicals, e.g. by phenolic glycolipid of M. leprae