Extracellular Immunity 1

Question 1

What are the 3 main groups of extracellular pathogens? (3)

Answer 1

Prokaryotes
Eukaryotes
Parasitic infections

Question 2

What are natural antibodies? (2)

Answer 2

Polyreactive, low affinity, germline encoded, IgM
Produced by CD5+ B-1a cells

Question 3

What are Innate defences? (1)

Answer 3

Phagocytic recognition (PRR and opsonisation) and concomitant antimicrobial mechanisms

Question 4

What are adaptive responses? (1)

Answer 4

T and B cells

Question 5

Describe TH2 response (2)

Answer 5

Driven by IL-4 and GATA3 mediated transcription
Generate neutralising antibodies

Question 6

What does class switching generate? (2)

Answer 6

Class switching generates high affinity IgA/IgG/IgE antibodies

Class switching of gut IgA1 to protease resistant IgA2

Question 7

What other cells do TH2 mediators activate that are non-B cells? (3)

Answer 7

IL-5
Eosinophils
IL-9 which activates basophils

Question 8

Describe TH17 immunity (4)

Answer 8

Involved in inflammatory response (recruitment of neutrophils):
dendritic cells produce cytokines - activate naive T cell to produce TH17 which activate neutrophils

Driven by IL-23, TGF-beta, IL-6 and RORy mediated transcription

Particularly important in antifungal and anti-bacterial immunity

Question 9

Virulence factors of group A streptococcus (7)

Answer 9

Bacterial adhesins and invasins- bind host cell
Complex capsule prevents phagocytosis
Surface M protein inactivates C3b, hypervariable
Secrets C5a protease, CD11b homologue
Streptolysins
Protein G
Streptococcal pyrogenic exotoxin B (SpeB), degrades IL-1β

Question 10

Consequences of infection (4)

Answer 10

Tissue necrocrosis
Rheumatic fever- due to molecular mimicry
Glomerulonephritis- immune complex
Toxic shock- non specific T cell activation

Question 11

What is a toxic shock? (3)

Answer 11

Superantigen triggers T-cells nonspecifically

Cross link T cells with dendritic cells which activates 90% T cells

Cytokine “storm” leads to multiple organ failure/death

Question 12

What are fungal infections? (2)

Answer 12

Mainly commensal
Require TH17, neutrophil/phagocyte response via PRRs

Question 13

Describe fungal recognition? (3)

Answer 13

Lectins (carbohydrate binding proteins) are able to recognise non-self sugars

Major receptor for B-glucan is Dectin-1

Skews towards Th17 response