IMI1: sensing damage protecting our bodies

Question 1

what cells are lymphoid cells?

Answer 1

T cells, B cells and NK cells

Question 2

what are the other major classes of cells?

Answer 2

myeloid cells (e.g. macrophages)
mast cells
DCs
neutrophils
basophils 
eosinophils

Question 3

what are NK cells?

Answer 3

large cytotoxic lymphocytes that patrol the blood for virally-infected of damaged cells which they are able to recognise despite lacking variable receptors like the ones found on B and T cells

Question 4

in what type of immunity is NK cells involved in?

Answer 4

it is involved in the innate immunity

Question 5

what are cytokines?

Answer 5

small polypeptides that are used as messengers in the immune system

Question 6

do we have the same number of microbes than body cells?

Answer 6

approximately yes

Question 7

are the microbes living in our body harmful?

Answer 7

no they are harmless. they live in symbiosis with us

Question 8

what is a microbiome?

Answer 8

microbiome is the genetic material of all of the microbes

Question 9

is the microbiome essential?

Answer 9

yes it is vital for the correct absorption of nutrients

Question 10

what are commensal bacteria?

Answer 10

bacterias and other microorganisms that act on host’s immune system to induce protective responses that prevent colonisation and invasion by pathogens

Question 11

what is the first line of defence of our body?

Answer 11

physical barrier: skin, mucous membranes, secretion (e.g. tears)

Question 12

what is the second line of defence?

Answer 12

innate immune system

Question 13

what does the innate immune system have to do?

Answer 13

needs to:

• defect
• deflect
• destroy

Question 14

is the action of the innate immune system broad or specific?

Answer 14

broad

Question 15

what is the third line of defence?

Answer 15

adaptive immune system

Question 16

is the adaptive immune system always deployed?

Answer 16

no, it is only deployed if it is absolutely necessary

Question 17

what are the organs of the immune system?

Answer 17

adenoids
tonsils
thymus
BM
bronchial-associated lymphoid tissue
axillary lymph nodes 
lymph nodes 
spleen
payer's patches
inguinal lymph nodes
appendix
lymphatic vessels

Question 18

how doe the innate immune system recognise the myriad of pathogens?

Answer 18

1st, the immune system recognise if something is harmless or dangerous:
the first cells pathogens encounter after physical barrier are resident macrophages that are present in all tissue

Question 19

what is phagocytosis?

Answer 19

process done by phagocytes where they gobble up pathogens or damaged cells and kill them using proteolytic enzymes and reactive oxygen species (ROS)

Question 20

how do macrophages recognise pathogens or damaged cells?

Answer 20

pathogens have structural features essential for their survival –> PAMPs (pathogen-associated molecular patterns)
damaged cells –> DAMPs (damage-associated molecular patterns)

Question 21

what are APC (=antigen presenting cells)? what do they do?

Answer 21

DCs and macrophages

they present antigen to T cells

Question 22

what are the 2 signals that the T cells need to get activated?

Answer 22

1. the antigen needs to be presented by major histocompatibility complex (MHC)
2. molecules on the APC that are called CD80 and CD86

Question 23

what are PRRs (pattern recognition receptors)?

Answer 23

family of receptors that recognise PAMPs and that control the activation of CD80 and CD86

Question 24

what are the 2 main groups of PRRs? and what do they do?

Answer 24

• signalling PRRs –> initiate signalling cascades

- phagocytic receptors –> trigger phagocytosis

Question 25

can signalling PRRs and phagocytic PRRs be soluble and cell-associated PRRs?

Answer 25

yes

Question 26

do each cell type express all innate receptors?

Answer 26

no, each cell type expresses just a few types

Question 27

what is cellular heterogeneity? how does it help cells?

Answer 27

certain functional immune cell type express different combinations of PRRs it increases cell's ability to identify non-self antigens or damaged cells

Question 28

what are other phagocytic receptors that macrophages express?

Answer 28

complement receptors and scavenger receptors

Question 29

what are the different types of cytokines?

Answer 29

- 40 interleukins (ILs) - chemotactic chemokines - antiviral interferons (IFNs)

Question 30

what are the manners in which cytokines act?

Answer 30

autocrine, paracrine or endocrine manner

Question 31

what does it mean for cytokines to have pleiotropic functions?

Answer 31

it means that they behave differently in different cells types and thus can have many different functions

Question 32

what do cytokines do in endothelium?

Answer 32

induce cell contraction and cytokine secretion

Question 33

what do cytokines do in macrophages?

Answer 33

induce cell activation

Question 34

what do cytokines do in DCs?

Answer 34

induce cell differentiation

Question 35

what do chemokine do in phagocytes?

Answer 35

induce cell migration

Question 36

what are the different pro-inflammatory cytokines? and what do they do?

Answer 36

IL-1beta, IL-6, IL-12, CXCL8 and TNF-alpha | they induce inflammation

Question 37

what dies inflammation causes?

Answer 37

causes local redness, swelling, less blood flow and vascular permeability

Question 38

what does permeability allow?

Answer 38

it allows the exit of neutrophils and other leukocytes from the blood and subsequent proliferation of NK cells

Question 39

macrophages release all types of pro-inflammatory cytokines. what do they each do?

Answer 39

IL-1beta and TNF-alpha --> induce blood vessels to become more permeable, enabling effector cells and fluid containing soluble effector molecules to enter the infected tissue IL-6 --> induces fat and muscle cells to metabolise, make heat and raise the temperature in the infected tissue CXCL8 --> recruits neutrophils from the blood and guides them to the infected tissue IL-12 --> recruits and activates NK cells that in turn secret cytokines that strengthen the macrophages' response to infection

Question 40

where can we find PRRs?

Answer 40

macrophages, DCs, NK cells, mast cells and neutrophils

Question 41

how is the precise immune response determined?

Answer 41

it is determined by the combination of PRRs

Question 42

what are the different PRRs?

Answer 42

CLR, NLR, TLR, RLR, cGAs and STING