Innate Immunity

Question 1

What are some characteristics of innate immunity?

Answer 1

fast, lacks specificity, lacks memory, no change in intensity

Question 2

What are some barriers to entry for pathogens?

Answer 2

physical: skin, mucous membranes, bronchial cilia

Physiological: diarrhoea, vomiting, coughing, sneezing

chemical: low pH in stomach, skin, vagina. antimicrobial molecules e.g IgA, lysozyme, mucus

normal flora: compete for site and resources and also synthesise vitamins

Question 3

What are some organisms found in the skin normally?

Answer 3

staph. aureus, staph epidermis, streptococcus pyogenes. candida albicans, clostridium perfringens

Question 4

What are some organisms found in the nasopharynx normally?

Answer 4

streptococcus pneumoniae, neisseria meningitidis, haemophilus species.

Question 5

What is the role of phagocytes in innate immunity?

Answer 5

second life of defence- recognise, engulf, degrade pathogens

Question 6

What are the different cells involved in phagocytosis?

Answer 6

macrophages: all organs, perform phagocytosis, APC’s to T cells, produce cytokines
monocytes: present in blood/ recruited at infection site and differentiate
neutrophils: recruited by chemotaxis to infection site where they ingest and destroy pyogenic bacteria e.g. staph aureus and strep pyogenes

Question 7

What are PAMPs and PRRs?

Answer 7

Phagocytes have PRRs (TLRs) that look oft pathogen associate molecular patterns (PAMPs) e.g endotoxins, carbs, lipids, proteins

Question 8

What are some examples of PRRs and PAMPs for gram negative bacteria?

Answer 8

Lipopolysaccharide (LPS)- TLR4
Lipoproteins and lipopeptides- TLR2
Porins

Question 9

What are some examples of PRRs and PAMPs for gram positive bacteria?

Answer 9

Peptidoglycan- TLR2

Lipoteichoic acids- TLR4

Question 10

What are some examples of PRRs and PAMPs for mycobacteria?

Answer 10

Lipoarabinomannan- TLR2

Mannose-rich glycans

Question 11

What are some examples of PRRs and PAMPs for bacterial flagella?

Answer 11

Flagellin-TLR5

Question 12

What is an opsonin?

Answer 12

coating proteins called opsonins that bind to the microbial surfaces leading to enhanced attachment of phagocytes and clearance of microbes e.g

C3b, IgG, CRP

Question 13

When are opsonins essential?

Answer 13

neisseria meningitides
streptococcus pneumoniae
haemophilus influenzae b

Question 14

What are some key cells in innate immunity aside from macrophages?

Answer 14

basophils/mast cells: early actors of inflammation (allergic response)

eosinophils: defense against multicellular parasites

natural killer cells: kill all abnormal host cells

dendritic cells: present microbial antigens to t-cells

Question 15

What is the complement system?

Answer 15

activated by microbes and cause recruitment of phagocytes, opsonisation of pathogens and killing of pathogens

Question 16

What is the MBL pathway in the complement system?

Answer 16

initiated when MBL binds to mannose residues of proteins e.g salmonella app., candida albicans

Question 17

What is the alternative pathway in the complement system?

Answer 17

initiated by cell surface microbial constituents (e.g endotoxins on E. Coli)

Question 18

Describe the antimicrobial actions of different complement proteins

Answer 18

C3a and C5a: Recruitment of phagocytes

C3b-C4b: Opsonisation of pathogens

C5-C9: Killing of pathogens, Membrane Attack complex

Question 19

What is the role of cytokines?

Answer 19

cause chemotraction between microbe and immune cells and also inflammation

Question 20

What are the antimicrobial actions of macrophage derived TNF-1, IL-1, IL-6?

Answer 20

Liver- crp and mbl

bone marrow- neutrophil mobilisation

inflammatory actions- vasodilation, vascular permeability, adhesion molecules

hypothalamus- increased body temperature