Detecting and responding to pathogens (Pattern Recognition Receptors)

Question 1

How are bacteria and fungi dealt with?

Answer 1

phagocytosis and killing

Question 2

How are viruses dealt with?

Answer 2

endocytosis, cellular shut-down, self-sacrifice, cellular resistance

Question 3

What are the problems with immunity?

Answer 3

• Immunity can take a long time but infections arrive quickly and unpredictably
• Adaptive immunological memory is highly specific, cross-reacting or self-targeting
• There a lot of bacterial species and viruses out there
• Only vertebrates have an adaptive system; there must be other effective immune systems

Question 4

What are the 2 types of pattern recognition receptors? (PRRs)?

Answer 4

1. Secreted and circulating receptors
2. Cell-associated PRRs

Question 5

What are secreted and circulating PRRs?

Answer 5

• Antimicrobial peptides secreted in lining fluids from epithelia and phagocytes

Question 6

What are examples of secreted and circulating PRRs?

Answer 6

Lectins and collectins (carbohydrate-containing proteins that bind carbohydrates or lipids in microbe walls)

Question 7

What do lectins and collectins do?

Answer 7

Activate complement, improve phagocytosis

Question 8

What are cell associated PRRs?

Answer 8

Receptors that are present on the cell membrane or in the cytosol of the cells
- recognise a broad range of molecular patterns

Question 9

What are the main family of cell associated PRRs?

Answer 9

TLRs (toll-like receptors)

Question 10

What is pattern recognition?

Answer 10

recognition of microbes and viruses depends on seeing ancient, conserved features of them

Question 11

How do TLRs recognise damage?

Answer 11

• TLRs also adapted to recognise a range of endogenous damage molecules, which may share characteristics of hydrophobicity
• TLR signalling by cellular damage products activates immunity to initiate tissue repair and perhaps enhance local antimicrobial signalling