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VBSC 211: The Immune System > Exam 8: Chapter 10 > Flashcards

Exam 8: Chapter 10 Flashcards

1
Q

How do most infectious pathogens enter the body?

A

Through mucosal tissues

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2
Q

What are mucosae?

A

Interfaces with our environment that are covered in mucus and contain 200x more lymphocytes than regular tissues

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3
Q

What are mucins?

A

Large glycoproteins that form networks of mucus

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4
Q

What are the two modes of action for mucins?

A

Secreted and membrane-bound

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5
Q

Why are the responses of the mucosal immune system different than the systemic immune system?

A

Mucosal immune cells are always encountering new antigens from pathogens, food, and commensal bacteria

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6
Q

What are the functions of commensal bacteria?

A
  1. Synthesize essential metabolites
  2. Break down plant fibers in food
  3. Inactivate toxic substances from food/pathogens
    4 Prevent pathogens from benefitting from human gut resources
  4. Interact with epithelium to trigger development of secondary lymphoid tissue
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7
Q

What architecture is seen in the gut?

A

Epithelium covered in mucus, lamina propria connective tissue beneath the epithelium

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8
Q

What are mesenteric lymph nodes and where are they located?

A

Mesenteric lymph nodes are the largest lymph nodes in the body, and they are located in the gut

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9
Q

What is the role of tonsils and adenoids?

A

To form a ring of lymphoid tissues around the entrance of the gut and airway

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10
Q

What is the importance of gut associated lymphoid tissues (GALTs)?

A

The location of numerous GALTs allows mucosal immune responses to occur locally rather than in a distant draining lymphnode

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11
Q

What are Peyer’s patches?

A

Primary GALTs found in the small intestine

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12
Q

What are Microfold (M) cells?

A

Specialized cells that are not covered in mucus and allow continual sampling of antigens and pathogens

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13
Q

What are probiotics designed to do?

A

Improve immune responses and prevent microflora changes caused by infection

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14
Q

What are the major differences between the system immune response and the mucosal immune response?

A
  1. Mucosal immune response is constantly activated
  2. Immune cells in mucosal tissues do not initiate an inflammatory response
  3. The TH1 response is rarely activated in mucosal tissues
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15
Q

What is the overall job of mucosal immunity?

A

To keep commensals and pathogens at bay

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16
Q

What do epithelial cells do once they identify a pathogen?

A

Locally express inflammatory cytokines and chemokines

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17
Q

How are pathogens and antigens brought into M cells for sampling?

A

Via transcytosis

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18
Q

What are isolated lymphoid follicles?

A

Small organs consisting of a single lymphoid follicle containing mostly B cells

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19
Q

What is the major GALT of the large intestine?

A

The appendix

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20
Q

What is the main difference between skin and mucosa?

A

Skin is designed to be impermeable, while mucosa actively samples antigens

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21
Q

How do dendritic cells respond to food?

A

Food is taken up by dendritic cells, brought to the mesenteric lymph node, and used to drive the differentiation of FoxP3+ T-regs

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22
Q

What immune response is elicited by commensals?

A

Commensals induce a TFH response when taken up by M cells that promotes the development of B cells that will become IgA secreting plasma cells

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23
Q

What role does dimeric IgA play in regards to commensals?

A

Dimeric IgA regulates the size of the commensal population

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24
Q

What immune response is elicited by pathogens?

A

Infection causes dendritic cells to move out of the lamina propria and GALT and capture pathogens, leading to the activation of a pathogen specific immune response

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25
Q

How do dendritic cells capture antigen from the gut lumen?

A

By extending processes across the epithelial layer

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26
Q

Where do dendritic cells move upon infection?

A

Into the epithelium

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27
Q

What happens to T and B cells that become activated in mucosal tissues?

A

They home as effector cells to the mucosal tissues

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28
Q

How do the effector cells of mucosal tissues know where to go?

A

Adhesion molecules and chemokines

29
Q

What regulates the induction of adhesion molecules and chemokine receptors for mucosal tissues?

A

Vitamin A metabolites (like retinoic acid)

30
Q

Why is the polio vaccine given orally?

A

The oral vaccine will establish effector memory cells that home to the mucosa, where the virus first infects cells

31
Q

What are intraepithelial lymphocytes?

A

A specialized population of CD8+ cells that can be either ab or gd T cells, have a limited TCR repertoire, and are found in the mucosal epithelium

32
Q

What property allows for a unified mucosal response?

A

Activated effector cells can recognize receptors in all mucosal tissues

33
Q

How are toxins and pathogens removed from the lamina propria?

A

Via IgA dimers undergoing active transport across the epithelium

34
Q

Does dimeric IgA activate complement or induce inflammation?

A

No

35
Q

What are the two subtypes of IgA?

A

IgA1 and IgA2

36
Q

What are the properties of IgA1?

A

Larger hinge region, interacts with pathogens more easily, more susceptible to protease cleavage

37
Q

What are the properties of IgA2?

A

Observed at higher levels in tissues with concentrations of bacteria, switch to IgA2 relies on cytokine APRIL

38
Q

How is IgA deficiency compensated for?

A

By secretion of IgM

39
Q

How can the effect of IgA deficiency be lessened?

A

By utilizing sanitary practices in food preparation

40
Q

What is the appropriate response to helminth infection?

A

TH2 cell response and IgE production

41
Q

What response to helminths try to produce?

A

A TH1 response, which causes tissue damage and ineffectively controls the infection

42
Q

What are goblet cells?

A

Cells that produce mucus

43
Q

What TH2 effector functions are wanted during a helminth infection?

A
  1. Increased cell turnover and movement to help shed parasitized cells
  2. Eosinophil production of MBP, which kills parasites
  3. IgE production
  4. Mast cell production of histamine and other inflammatory cell recruiters
44
Q

What TH1 effector functions are NOT wanted during a helminth infection?

A

Macrophage activation and complement fixation

45
Q

What is one example that proves the co-evolution of innate and adaptive immunity?

A

Innate immune cells have acquired Fc receptors that recognize antibodies generated by the adaptive immune response

46
Q

How are gd T cells and ab T cells different?

A
  1. gd T cells are not subject to positive and negative selection
  2. antigens recognized by gd T cells do not require MHC presentation
  3. gd T cells recognize phosphoantigens, which are pathogen specific metabolites rather than peptides
47
Q

What V segment rearrangement is typically seen in gd T cells?

A

Vg9, Vd2

48
Q

What receptors are and are not present on gd T cells

A

Chemokine receptors to help gd T cells be recruited into the LN are NOT present; receptors that allow gd T cells to find the site of infection ARE present

49
Q

What functions can gd T cells carry out?

A
  1. Produce IFN-gamma and TFN-alpha
  2. Kill cells by secreting granulysin
  3. Become antigen presenting cells
  4. Activate dendritic cell maturation
  5. Activate ab T cells
  6. Activate memory T cells
50
Q

What response is generated by the binding of MIC antigen with both Vg:Vd1 TCR and the NKG2D receptor?

A

A synergistic response that is better than either binding interaction alone

51
Q

What cells other than gd T cells can also identify MIC antigen?

A

NK cells and CD8+ T cells that express NKG2D receptors

52
Q

How does CD56 expression classify NK cells?

A

NK cells high in CD56 are immature, while NK cells low in CD56 are mature

53
Q

Which NK cells are cytotoxic?

A

Mature CD56low cells

54
Q

What are the two types of NK cell receptors in humans, and where are they found?

A
  1. Lectin like receptors - found in NKC region

2. Killer immunoglobulin receptors (KIRs) - found in LRC region

55
Q

What are the ligands for NK cell receptors?

A

MHC class 1 molecules

56
Q

What does it mean for NK cell receptors to be variegated?

A

Each cell expresses a different subset of receptors

57
Q

Are Fc receptors or NK cell receptors more efficient at activating NK cells

A

Fc receptors (in the presence of IgG)

58
Q

How do NK cells monitor class 1 expression?

A

By recognizing HLA-A, B, and C leader peptides presented by HLA-E

59
Q

What interaction allows NK cells to indirectly measure the amount of class 1 on cell surfaces?

A

The interaction between HLA-E and CD94:NKG2A

60
Q

What is the role of NKG2A’s ITIM motif?

A

To inhibit signaling

61
Q

What infection response allows NK cells to target infected cells?

A

Pathogen-dependent down-regulation of MHC class 1 and up-regulation of MIC

62
Q

Why can specific residues affect whether a KIR can recognize the allotype?

A

Because KIR binding only sees part of the class 1 molecule

63
Q

Why are NK cells “educated?”

A

So they can recognize the different alleles present on MHC class 1 and thus recognize healthy vs unhealthy cells

64
Q

What is the first inhibitory receptor expressed by NK cells?

A

CD94:NKG2A

65
Q

What happens to CD94:NKG2A if the NK cell begins to express other inhibitory receptors?

A

It is turned off

66
Q

What molecules present lipid antigens?

A

Non-canonical class 1 molecules of the CD1 family

67
Q

What cells express CD1 molecules?

A

Those infected by mycobacterium

68
Q

Which CD1 isoform presents lipid ligands to T cells with NK receptors (NKT cells)?

A

CD1d

69
Q

What V-J arrangement is typically seen in NKT cells?

A

Va24-Ja8, combined with a variety of beta chain arrangements

VBSC 211: The Immune System (10 decks)

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