A2 innate immunity

Question 1

innate vs adaptive

Answer 1

innate
-inherited (germ-line coded)
-recognition of common microbial motifs
adaptive
-random generation of recognition
-generates diversity of cells, can respond too very specific parts of pathogens

Question 2

components of innate immune system

Answer 2

anatomical barriers
inflammation
complement
wbc
-macrophages, neutrophils, basophils, eosinophils, mast cells, nk cells

Question 3

anatomical barriers (mechanical)

Answer 3

skin, gut, lungs, eyes/nose
-epithelial cells joined by tight junctions
skin and gut
-longitudinal flow of air or fluid
lungs
-movement of mucus by cilia
eyes/nose
-tears, nasal cilia

Question 4

anatomical barriers (chemical)

Answer 4

skin, gut, lungs
-antibacterial peptides
skin
-fatty acids
gut
-low pH
-enzymes (pepsin)
eyes/nose
-enzymes in tears (lysozyme)

Question 5

anatomical barriers (microbiological)

Answer 5

skin, gut
-normal flora

Question 6

inflammation

Answer 6

recognition of pathogen associated molecular patterns (PAMPS) binding to pathogen recognition receptors (PRRs)
-TLR, CLR, NOD
activation of innate cells
-macrophages and mast cells
release of inflammatory mediators that recruit innate cells and lymphocytes

Question 7

pattern recognition

Answer 7

innate immune system detects molecules from pathogens or damaged cells
-PRRs
many pathogens use similar mols that are distinct from eukaryotes
-pathogen associated molecular patterns (PAMPs)
-damage associated molecular patterns (DAMPs)

Question 8

examples of pattern recognition receptors

Answer 8

toll-like receptors (TLRs0
-protein
-recognise leucine repeats
-virusus, bacteria, fungi, damaged cells

c-type lectin receptors (CLR)
-recognise carbohydrates
-viruses, bacteria, fungi, parasites, cancer

NOD-like receptors (NLR)
-recognise peptidoglycans
-bacteria

Question 9

consequence of TLR stimulation

Answer 9

-often cell activation
-causes cell to secrete chemokines and cytokines
(recruitment of more phagocytes and inflammation)
-allows cell to increase phagocytosis and intracellular killing
1. macrophage expresses receptors for many bacterial constituents
2. bacteria binding to macrophage receptors initiate the release of cytokines and small lipid mediators of inflammation

Question 10

what cells carry out phagocytosis

Answer 10

innate cells
-PMN, macrophages, dendritic cells
-termed phagocytes

Question 11

step names of phagocytosis

Answer 11

-recognition
-pseudopod formation
-ingestion
-phagosome
-phagosome/lysosome fusion
digestion

Question 12

stages of phagocytosis (detail)

Answer 12

1. chemotaxis and adherence of microbe to phagocyte
2. ingestion of microbe by phagocyte
3. formation of phagosome
4. fusion of phagosome with lysosome to form phagolysosome
5. digestion of ingested microbe by enzymes
6. formation of residual body containing indigestible material
7. discharge of waste materials

Question 13

what do phagocytes need in order to start destruction

Answer 13

recognition requires receptors on cell surface of phagocyte to bind pathogen
sometimes opsonisation
eg PRRs such as TLRs

Question 14

recruitment of cells- rolling

Answer 14

adhesion of mols slow blood cells
using selectins binding to lectins on target cell
diff combinations of selectins- selective recruitment of cells

Question 15

recruitment of cells- extravasation

Answer 15

-once leukocyte has slowed down, other adhesion mols can allow attachment
-integrins (LFA-1) and cell adhesion mols (CAMs, ICAM)
-allows cell to stick and axtravaste
(ie passes through endothelial cells lining the blood vessel)

Question 16

recruitment of cells- chemokines

Answer 16

migration influences by chemokines
small proteins that control cell movement- chemotaxis
different chemokines recruit different cells to different tissues
-ie IL8/CXCL8

Question 17

complement summary

Answer 17

collection of serum proteins
activated by a number of factors
causes serial activation of proteases
several functional outcomes

Question 18

classical pathway

Answer 18

antigen antibody complex
complex activation
recruitment of inflammatory and immunocompetent cells

Question 19

lectin pathway

Answer 19

lectin binding to pathogen surfaces
complement activation
opsonisation of pathogens

Question 20

alternative pathway

Answer 20

pathogen surfaces
complement activation
killing of pathogens

Question 21

cell recruitment & activation and opsonisation stages

Answer 21

-bacterium is coated with complement by the alternative and MBL pathways
-when only C3b binds to CR1, bacteria are not phagocytosed
-C5a can activate macrophages to phagocytose via CR1

Question 22

direct killing of bacteria stages

Answer 22

-C5b binds C6 and C7
-C5b67 complexes bind to membrane via C7
-C8 binds to comp and inserts into cell membrane
-C9 mols bind to the comp and polymerize
-10-16 mols of C9 bind to form a pore in membrane

Question 23

inflammation pillars

Answer 23

calor- heat
rubor- redness
tumor- swelling
dolor- pain
functi olaesa- loss of function

Question 24

what bridges innate and adaptive systems

Answer 24

breakdown of pathogens generates lots of antigens
these represent fragments of the various proteins expressed by pathogen
can be recognised by adaptive immune system
(covid mutating and changing)