Innate Immunity 1

Question 1

How does pathogen recognition work?

Answer 1

pathogens share molecules called pathogen associated molecular patterns
PAMPS are recognized by pattern recognition receptors on innate immune cells

Question 2

PAMPs

Answer 2

unique to specific classesof microbes
essential
approx 1,000 different patterns
e.g. lipopolysaccharide, gram negative
peptidoglycan, gram positive

Question 3

Other patterns recognized by PRRs

Answer 3

damage associated molecular patterns released by damaged host cells
foreign bodies, environmentally/endogenously derived crystals, sutures etc.

Question 4

PRRs

Answer 4

expressed on many different cell types
same set of receptors on all cells of the same type
PAMP-PRR interaction causes rapid response

Question 5

Types of PRRS

Answer 5

Toll like receptors - variety of surface antigens
Lectin-like receptors - bacterial or fungal polysaccharides
NOD-like receptors - bacterial antigen
RIG-like receptors- viral genetic material (RNA)

Question 6

Innate immune cells

Answer 6

Neutrophils, macrophages - phagocytosis
Mast cells, basophils, eosinophils - degranulation
Natural killer cells - cytotoxicity
Dendritic cells - lymphocyte activation

Question 7

Phagocytes

Answer 7

Ingestion - phagosome formation
fusion of phagosome and lysosome
destruction of phagocytosed organism/particle :low pH, antimicrobial peptides and enzymes, NO, ROS
exocytosis

Question 8

What is phagocytosis enhanced by?

Answer 8

Opsonisation

Question 9

Opsonins

Answer 9

Tag a pathogen as foreign
establish a tight link between pathogen and phagocytic cells
neutralise the surface charge
change microbial surface from hydrophilic to hydrophobic
facilitate phagocytosis
e.g. antibodies, lysozymes, lectins

Question 10

Neutrophils

Answer 10

phagocytes
10-20um polymorphonuclear granulocytes
30-70% of circulating leukocytes
most mobile peripheral leukocyte
1st line defense mechanism
mediate early phases of inflammation
short life span
incapable of sustained phagocytic effort

Question 11

What are the functions of neutrophils?

Answer 11

phagocytosis
degranulation
iron sequestration
neutrophil extracellular trap formation

Question 12

Macrophages

Answer 12

phagocytes
immature bloodstream form: monocyte
10-15 um
kidney bean shaped nuclei
2 to 8% circulating leukocytes

Question 13

Migration of macrophages

Answer 13

monocytes migrate into tissues - mature resident tissue macrophages
lymph nodes and spleen

Question 14

What are the functions of macrophages?

Answer 14

M1 macrophages: phagocytosis
M2 macrophages - tissue repair

removal of dead/damaged cells
antigen representation and activation of other immune cells
cytokine secretion