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VET 413: Infectious Disease/Immunology > Immunology & Immune Responses > Flashcards

Immunology & Immune Responses Flashcards

1
Q

is the innate immune system specific? fast or slow?

A

no - nonspecific responses

rapid - immediate/near immediate

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2
Q

what are examples of innate immune components

A

lymphoid and non-lymphoid tissues
- physical barriers
- pH
- mucosal antibacterial products
- complement system

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3
Q

what are the innate immune cells

A

neutrophils
macrophages
NK cells
innate lymphoid cells (ILCs)

dendritic cells - act as a messenger to activate adaptive immune response

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4
Q

do innate immune cells have memory

A

no - only act as effective pathogen killers

can easily get overwhelmed by pathogen virulence factors and abundance

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5
Q

what are the types of innate immune receptors

A
  1. toll like receptors
  2. C type lectin receptors
  3. NOD like receptors
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6
Q

toll-like receptors

A

recognize specific components on pathogen cell surfaces (PAMPs, DAMPs, MAMPs)

first trigger that initiates an immune response

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7
Q

what does TLR4 recognize

A

LPS on gram negative bacteria

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8
Q

what does TLR2 recognize

A

lipoteichoic acids on gram positive bacteria

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9
Q

what does TLR5 recognize

A

flagellin on flagellated bacteria (gram positive or negative)

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10
Q

c type lectin receptors

A

recognize fungal and mycobacterial components

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11
Q

NOD like receptors

A

protect from inside the cell

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12
Q

DAMPs

A

damage associated molecular patterns

released by a cell after inappropriate cell death (NOT released during regular apoptosis)

regular cell components that should only be inside the cell

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13
Q

innate immune system characteristics

A
  • specificity is inherited
  • triggers immediate response
  • recognizes broad class of antigens
  • discriminates closely related molecular structures

NOT:
- encoded in multiple gene segments
- require gene rearrangement
- undergo clonal expression

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14
Q

adaptive immune system characteristics

A
  • encoded in multiple gene segments
  • require gene rearrangement
  • undergo clonal expression
  • able to discriminate closely related molecular structures

NOT:
- specificity inherited in genome
- triggers immediate response
- recognize broad classes of pathogens

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15
Q

what are the three consequences of innate immune activation

A
  1. tissue macrophages destroy pathogen
  2. macrophages signal for help by using local cytokine and chemokine production
  3. dendritic cells capture antigen and go to LNs to activate adaptive system
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16
Q

effect of macrophage recognition

A

pathogen binds TLR on macrophage surface and gets phagocytoses into phagosomes

phagosomes fuse with lysosome to initiate breakdown of pathogene

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17
Q

effect of local cytokine/chemokine production

A

vasodilation and increased adhesion molecules
- attracts innate cells and stimulates extravasation to tissues

systemic effects: fever

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18
Q

effect of dendritic cells

A

immature DCs located in the tissues capture pathogens and become activated

travel to draining LNs to present antigen to T cells

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19
Q

changes in dendritic cells once activated

A
  1. lose phagocytic capability
  2. increase CCR7
  3. increase MHC II
  4. increase B7 molecules
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20
Q

CCR7

A

specific chemokine receptor that directs activated DCs to the T cell area of the lymph node

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21
Q

B7 molecules

A

CD80 and 86; costimulatory molecules required to present antigen to T cells

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22
Q

clonal selection theory

A

development of an appropriate effector lymphocyte requires:
1. thymus: single progenitor gives rise to many lymphocytes with different specificities –> self reactive lymphocytes are removed via deletion –> non self-reactive lymphocytes go to LNs

  1. lymph nodes: naive lymphocytes detect antigen –> lymphocyte activates –> proliferation and differentiation
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23
Q

how long does it take for lymphocytes to proliferate/undergo clonal expansion

A

7-10 days

innate immune system protects body in the meantime

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24
Q

lymphocyte recirculation

A

lymphocytes enter circulation through thoracic duct

lymphocytes exit circulation and enter lymphatics through high endothelial venules into the paracortex of the LN

25
Q

where are the only sites that naive lymphocytes can be found

A

blood
lymphatics
lymphoid tissues

26
Q

what are the three signals for T cell activation

A
  1. antigen presentation
  2. costimulation
  3. differentiation
27
Q

T cell signal 1: antigen presentation

A

TCR + CD4/8 on T cell binds to antigen peptide + MHC II/I on dendritic cell

28
Q

CD4 vs CD8 T cell activation

A

CD4: detects extracellular antigen peptide bound to MHC II

CD8: detects intracellular antigen peptide bound to MHC I

29
Q

T cell signal 2: costimulation

A

CD28 on T cell binds B7 on dendritic cells

indicates presence of inflammation at the site of the foreign antigen

30
Q

what happens if there is no signal 2

A

tolerance - no costimulation means that the antigen peptide is not eliciting a local immune response in the tissues, no responding T cells get deleted to prevent damage

31
Q

CTLA-4

A

negative regulator of T cell activation

binds B7 with greater affinity than CD28

ONLY expressed as T cells start proliferating to prevent over-cloning the T cells

32
Q

what is the most polymorphic part of the genome

A

MHC genes

high polymorphism allows a species to be able to respond to a wide variety of genes

33
Q

effect of inbreeding on immune response

A

inbreeding causes decreased polymorphism of MHC molecules, which means inbred populations will have MHCs that are responsible for the same pathogens –> decreased ability of the immune system to respond to a variety of pathogens

34
Q

MHC restriction

A

T cells will only respond to antigen peptide presented on MHC if they recognize both the self (MHC) and non-self (antigen peptide) components

prevents overproduction of T cells in response to the same pathogen

35
Q

peptide binding groove

A

site where the antigen binds the MHC

MHC variability allows for recognition of diverse pathogens

36
Q

superantigens

A

pathogen products that can activate many T cells by binding the TCR and MHC outside of the peptide binding groove

causes over-activation of T cells leading to a massive inflammatory response

37
Q

T cell dependent B cell activation

A

two signal process of activating B cells that involves T cells

  1. BCR binds antigen
  2. CD40 on B cell binds CD40L on T helper cells
  3. cytokines secreted from T follicular helper cells drives class switching
38
Q

B cell signal 1

A
  1. antigen enters LN through afferent lymphatics
  2. subcapsular macrophage bind antigen without phagocytosing
  3. passes antigen to follicular dendritic cells in the LN follicle
  4. follicular dendritic cells present antigen to naive B cells
  5. BCR on B cell binds the native (unprocessed) antigen
39
Q

how do B cells move to the B cell area of the lymph node

A

express CXCL5

40
Q

how do B cells move to the B/T cell border

A

once B cell binds antigen, it expresses CCR7 to move towards the paracortex

41
Q

how do T cells move to the B/T cell border

A

differentiated and activated T helper cells express CXCR5 to move towards the follicle

42
Q

B cell signal 2

A
  1. B cells ingest antigen and present antigen peptide on MHC II to CD4 T cells
  2. TCR and CD4 on T cell bind antigen peptide on BCR to activate the B cell
  3. CD40 on B cell binds CD40L on T helper cells to co-stimulate B cell activation
43
Q

clonal expansion of B cells

A
  1. activated B cells start to proliferate inside the follicle, forming a germinal center
  2. cells in germinal center form a light and dark zone to undergo somatic hypermutation and class switching
  3. some B cells move out of the follicle and form a primary focus to release early antibodies
  4. remaining B cells in germinal center form plasma cells or memory B cells and exit the LN
44
Q

somatic hypermutation

A

mutation of the antigen binding region on the BCR

45
Q

class switching

A

functional modification of the back end of the receptor (IgG, IgM, IgA, IgE)

46
Q

dark zone

A

“centroblast”

site of B cell proliferation, somatic hypermutation, and class switching
- creates a higher affinity receptor

B cells must express CXCR4 to remain in the dark zone

47
Q

light zone

A

centrocyte

site of testing; follicular Th cells and follicular DCs in the light zone present antigen to test the new receptors using signal 1 and 2

higher affinity BCRs outcompete lower affinity

48
Q

naive B cell characteristics

A
  • express surface Ig
  • express surface MHC
  • do not secrete antibodies
  • somatic hypermutation and class switching
49
Q

plasmablast characteristics

A
  • express surface Ig
  • express surface MHC
  • secrete EARLY antibodies
  • class switch
50
Q

plasma cell characteristics

A
  • no surface Ig
  • high rate of antibody secretion
  • no somatic hypermutation or class switching
51
Q

memory B cell characteristics

A
  • express surface antibody
  • do not secrete antibody
52
Q

what are the major blood antibodies

A

IgM and IgG

53
Q

what is the most abundant immunoglobulin

A

IgA

54
Q

IgA

A

present on external mucosal surfaces (lung, gut)

does NOT fix and activate complement to avoid inflammation at mucosal surfaces

55
Q

what are the 3 methods of antibody protection

A
  1. neutralization
  2. opsonization
  3. complement activation
56
Q

neutralization

A

antibodies bind toxins to prevent them from binding to host cells

57
Q

opsonization

A

bacteria get coated with antibody –> antibody binds Fc receptors on macrophages –> macrophage membranes fuse and create a phagosome –> lysosomes fuse to phagosome and degrade bacteria

58
Q

complement activation

A

IgM and IgG bind to antigens on bacteria surface to initiate complement cascade

enhances opsonization and lysis of bacteria

VET 413: Infectious Disease/Immunology (38 decks)

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