Innate immunity

Question 1

Innate vs adaptive immunity

Answer 1

Innate
-born with
-broad specificity
-rapid response

Adaptive
-acquired over time
-v. specific
-enhanced by prior contact (memory)
-slower response

Question 2

What is the innate immune system made up of?

Answer 2

-barriers (skin, muc surfaces, etc)
-leukocytes (phagocytes, NK cells)
-soluble proteins (complement, interferons)
-local and systematic responses (inflammation and fever)

Question 3

What physical barriers are there?

Answer 3

-epithelial cells w/tight junctions
-air/fluid flow
-cilia (resp tract)

Question 4

What chemical barriers are there?

Answer 4

-antibacterial peptides
-fatty acids (skin)
-low pH (GI and UG tract)
-lysozymes (resp tract)

Question 5

What microbiological barriers are there?

Answer 5

-commensals (in skin and tracts)

Question 6

What soluble proteins are involved in the innate immune response?

Answer 6

defensins
interferons (viral infections)
complement (extracellular infections)

Question 7

What are defensins?

Answer 7

+ve charged soluble peptides prod by neutrophils that disrupt bact membrs

Question 8

What are interferons?

Answer 8

soluble proteins (group of cytokines!) prod by all nucleated cells (IFNβ; IFNα made by RBCs) when under viral infection
-increase MHC1 expression (antigen presentation), activating more NK cells

Question 9

What is complement?

Answer 9

proteins activated in response to pathogen
-causes inflammation, opsonisation of gram +ve bact and induces gram -ve bact cells to lyse

Question 10

What happens in inflammation?

Answer 10

localised response caused by complement
-blood vessels dilate and capillaries become more permeable
-phagocytes migrate into tissues
-causes heat, redness, swelling, pain

Question 11

What happens in fever response?

Answer 11

systematic response caused by cytokines, LPS
-prostaglandin synthesised and acts on hypathalamus

Question 12

What are pattern recognition receptors (PRPs)?

Answer 12

receptors that recognise microbe-associated molecular patterns (MAMPs) and initiate phagocytosis, chemotaxis and signalling

eg. toll-like receptors signal presence of microbes (specific) - dimerise and initiate response

Question 13

What are microbe-associated molecular patterns (MAMPs)?

Answer 13

molecular structures conserved across many microbes which are critical for pathogen’s survival/function but are distinct from humans
eg. LPS, chitin, dsRNA

Question 14

What bactericidal agents are present in lysosomes/phagosomes of phagocytes?

Answer 14

-enzymes (lysozymes, acid hydrolyses)
-competitor proteins (lactoferrin)
-antimicrobial peptides (defensins)
-toxic oxygen-derived products
-toxic nitrogen oxides

Question 15

What are cytokines?

Answer 15

“hormones” of immune system which regulate cell behaviour and gene expression to regulate immune responses
-made by T cells (and other cells)
-act locally (sometimes systematically eg. fever)
-act on cells w/specific cytokine receptors

egs. interleukins, interferons, chemokines, tumour necrosis factors

Question 16

What are chemokines?

Answer 16

group of cytokines that control cell movement/chemotaxis
eg. IL-8

Question 17

What are interleukins?

Answer 17

group of cytokines which act on cells (eg activate) generally made by T cells
eg. IL-1, Il-38

Question 18

What are tumour necrosis factors?

Answer 18

group of cytokines that cause inflammation and can kill some cells

Question 19

What are the consequences of compliment activation?

Answer 19

-activation of cells for chemotaxis and mast cells (inflammation) -> C3a and C3b
-opsonisation (increased recognition by phagocytes) -> C3b
-cell lysis (pores formed, inducing lysis) -> membrane attack complex

Question 20

What is the role of the innate immune system?

Answer 20

-first-line of defence
-rapid, non-specific response
-either deals with infection or induces adaptive response