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MICR 341 > Immune System > Flashcards

Immune System Flashcards

1
Q

what is the difference between the innate and adaptive immune systems?

A

The innate immune system has unspecified defenses that are always ready, while the adaptive immune system has specific defenses, which need time to react.

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2
Q

what is the innate immune system composed of?

A 
phagocytic cells (monocyte, macrophage, neutrophil)
natural killer cells
accessory proteins (complement, cytokine, chemokine)
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3
Q

when is the innate immune system needed?

A

when the bacteria breach the first defense ie skin and mucosa

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4
Q

what are cells of the innate immune system?

A 
neutrophil (PMN)
basophil
DC
monocyte
macrophage (differentiated monocyte)
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5
Q

which cells are part of both the innate and adaptive immune system?

A

macrophage and DC because they present the antigen

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6
Q

what are the 3 pathways that activate the complement system?

A

mannose-binding lectin pathway
classical pathway
alternative pathway

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7
Q

C3a

A

induces the release of vasoactive

molecules (histamine) by mast cells.

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8
Q

C3b

A

opsonizes (marks for ingestion/elimination by phagocytes) the bacterial invader.

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9
Q

C5a

A

attracts phagocytes to the site of infection.

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10
Q

classical pathway

A

antibodies attach to the bacteria, activating C1
which activates C2 and C4 creating a C3 convertase (C4bC2a). C5 convertase (C4bC2aC3b) is created. C5b attaches to LPS and recruits components to form MAC

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11
Q

alternative pathway

A

bacterial surface molecules (B factor) bind to C3.
-C3 is spontaneously converted to C3a and C3b. Factor B adds creating 3 convertase (C3bBb) etc. (C5 convertase = C3bBbC3b)

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12
Q

mannose-binding lectin pathway

A

mannose-binding lectins bind to mannose on the bacterial surface and activate C2 and C4 etc. (classical)

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13
Q

what is opsonization

A

marking of bacterial pathogens for ingestion by phagocytes. The phagocyte contains receptors for the molecule bound to the pathogen (antibody C3b)

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14
Q

what does MAC stand for and do?

A

membrane-attack complex

forms pores in the bacterial membrane

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15
Q

H factor

A

when there is no foreign bacteria, no MAC complexes need to form and no opsonization of pathogens needs to take place. The H factor binds to sialic acid and when C3b is activated it binds to the H factor. This complex recruits the I factor and destroys C3b. (safeguard)

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16
Q

are host cells opsonized?

A

NO

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17
Q

B factor

A

B factor binds to bacterial surface. Activated C3b can bind to LPS and TA on the surface of bacteria and interact with Bb that ultimately leads to the formation of a C5 convertase.

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18
Q

How are host cells protected

A

sialic acid. the surface of host cells are coated in glycoproteins

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19
Q

How does a capsule protect the bacteria?

A
  • form a protective coating around the bacteria. Unstructured network of polymers
  • protect it from inflammation (antimicrobial peptides, lysozyme)
  • capsule has a low affinity for the B factor and high affinity for the H factor
  • Example: some capsules are composed of sialic acid
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20
Q

what are cytokines and chemokines?

A

soluble proteins or glycoproteins produced by cells of the immune system (monocytes, macrophages, neutrophils, lymphocytes, endothelial cells, epithelial cells, fibroblasts, etc.)

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21
Q

Cytokines

A
  • responsible for the onset of symptoms such as redness, swelling, pain and fever.
  • mediate the inflammatory response
  • activate the cells of the innate and adaptive immune systems
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22
Q

chemokines

A

attract the cells of the immune system to the site of infection and make them more active.

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23
Q

PAMPs

A

Pathogen-associated molecular patterns

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24
Q

what is the complement system?

who does it affect?

A

set of proteins that creates pores in the pathogen membrane and induces lysis
affects gram negative, no affect on gram pos

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25
Q

what are examples of PAMPs

A

flagella, peptidoglycan, LPS, LTA, CG rich DNA

26
Q

what does TLR stand for?

What do they do?

A

toll-like receptor

membrane receptors - mediate the response of the cells to the presence of EXTRACELLULAR PAMPs from bacteria

27
Q

which TLR recognizes flagella? LPS?

A

TLR5

TLR4

28
Q

Inflammation

A

response of vascular tissue to harmful stimuli (damage to tissue and PAMPs)

29
Q

TNFalpha, IL1

A

proinflammatory cytokines

mast cells, DCs phagocytes

30
Q

what are examples of anti-inflammatory cytokines

A

IL4, IL10, IL1-receptor antagonist

Reduce inflammation

31
Q

chemotaxis

A

Monocytes and neutrophils are attracted to the site of infection

32
Q

transmigration

A

the process that macrophages and neutrophils travel from the blood stream to the tissue

33
Q

what facilitates transmigration?

A

vasodilation: blood vessels become more leaky due to a release of histamine by mast cells in response to PAMPs and C3a

34
Q

What happens when immune cells enter the tissue?

A

monocytes differentiate into macrophages when they enter the tissue. monocytes and neutrophils become activated

35
Q

What are the steps to phagocytosis?

A

actin, phagolysosome

36
Q

NET?

A

a neutrophil extracellular trap
composed of chromatin covered in antimicrobial enzymes
-inactivates virulence factors
-kills microbes

37
Q

adaptive immune system

A
  • remembers the microbes it has encountered before ie the second wave has a much faster response time
  • specific
38
Q

what produces antibodies?

A

MATURE B Lymphocytes

39
Q

what are the domains of antibodies?

A
  • antigen binding site (Fab)
  • constant region - binds to C1 and Fc receptor
  • antibody is a monomer
40
Q

epitope

A

specific region of the antigen that the antibody binds to

41
Q

Fab domain

A

there is a constant region and a variable region (Fv)

42
Q

IgM

A
  • found in blood and extravascular tissues, breast milk

- 1st antibody to be produced by the adaptive immune response by a NEW antigen

43
Q

IgG

A
  • produced in subsequent or sustained infections
  • produced after IgM
  • only type of antibody that can cross the placental barrier
44
Q

what is the main antibody in the secondary response

A

-IgG

45
Q

sIgA

A
  • secreted into the mucosal surfaces to trap pathogens because the Fc region binds to mucin
  • secreted in all body fluids
46
Q

antigen-presenting cells?

A

macrophages, DC, B cells

47
Q

who produces MHC-1

A

produced by all nucleated cells

intracellular stimuli

48
Q

who produces MHC-2

A

produced only by professional phagocytes - antigen presenting cells
extracellular stimuli

49
Q

APCs are activated by what?

A

Il-1

50
Q

who activates T-cells?

A

APCs

51
Q

Natural Killer Cells

A

-activated by binding to host cells

52
Q

how can activation of NK cells be stopped

A

binding of MHC1 to an inhibitory receptor on the surface of NK cells

53
Q

when are NK cells activated and what do they do?

A

-activated when there are no or low levels of MHC 1
(pathogens that do not have MHC1)
-NK cells release intracellular granules containing
1. perforins that create channels in the host membrane
2. proteases and granzymes which exit through the host membrane and initiate apoptosis (controlled cell death)

54
Q

CTLs (CD8

A
  • activated by APCs
  • infect cells that display a specific antigen
  • they have receptors that are specific for a particular epitope from a microbial antigen
55
Q

How do CTLs destroy pathogens?

A
  1. granzymes and perforins

2. granulysin kills intracellular bacteria by a pore forming action

56
Q

presentation of MHC II stimulates which cells?

presentation of MHC I stimulates which cells?

A

CD4 Thelper cells

CD8 CTL

57
Q

what do lymph nodes contain?

A

immune cells - macrophage, DC, Tcells Bcells

58
Q

Bacterial infection of the lymph nodes

A

macrophages quickly kill bacteria that enter lymph tissue

bacteria that survive in the lymph reproduce inside macrophages (yersina pestis)

59
Q

function of lymph nodes?

A

filters of the lymphatic system

60
Q

role of the lymphatic system?

A

The role of the lymphatic system is to prevent the buildup of fluids in the tissues and to recycle blood proteins. The lymphatic system drains excess fluid in the tissue, filters it and returns it to the blood. (many cells and proteins leak out of blood vessels due to the inflammation response)

MICR 341 (7 decks)

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