Blood and immune: infection and innate immunity

Question 1

main types of pathogens

Answer 1

1. virus - intracellular pathogen (flu, polio, smallpox etc.)
2. bacteria - mostly extracellular (plague, cholera, staph)
3. protozoa and parasites - complex multicellular

Question 2

defence according to pathogen

Answer 2

1. virus - antibodies and cellular immunity (distinguish between infected vs normal cells
2. bacteria - primarily mediated by innate and phagocytosis
3. parasites - require direct killing by chemical mediators from specialist myeloid cels

Question 3

FcR (antibody) mediated phagocytosis

Answer 3

1. antibody (IgM, IgG) bind to bacterial antigens
2. excpose antibody to Fc region
3. neutrophil’s Fc receptor binds to FC
4. activates phagocytosis
5. phagosome formed
6. phagolysosome formed
7. phygolysosome acidifies and kills bacteria

Question 4

two main bacteria positives

Answer 4

gram positive - thick peptidoglycan wall (requires phagocytosis)
gram negative - thin peptidoglycan layer surrounded by an outer membrane (lysed directly by complement attack complex)

Question 5

extravasation

Answer 5

how neutrophils find infections from confines of blood vessel
1. activation - injury/inflammation activates adjacent capillary epithelial cells
2. tethering - selectins bind to neutrophils and they slow down
3. adhesion - binding to integrins and ICAM-1 causes neutrophil to stop moving and flatten
4. diapedesis 0 neutrophil squeezes between endothelial and into interstitial space
5. chemotaxis - neutrophil migrates along chemical gradient to site of infection

Question 6

opsonisation

Answer 6

the tagging of pathogens during complement for phagocytosis/immune response

Question 7

molecular pattern recogisiton

Answer 7

pattern recognition receptors (PRR) bind to unique molecules of microbes
toll-like receptors are best known (TLR)
activation through TLR stimulates strong innate response through inflammation pathway

Question 8

Pathogen associated molecular patterns

Answer 8

unique molecules to microbes for PRR recognition
structurally complex
evolutionarily stable
stimulate adaptive response

Question 9

TLR4 (LPS)

Answer 9

receptor for lipopolysaccharide wich is a componant of gram-negative bacteria membrances
LPS can cause septic shock
TLR4 stimulates immune response for LPS

Question 10

complement receptors

Answer 10

CR1, CR2, 3, 4
myeloid cell receptors that bind activated complement components on bacteria
cross linking of the surface CRs initiates phagocytosis