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Immunology Exam One > Antigen Presentation > Flashcards

Antigen Presentation Flashcards

1
Q

What is an antigen?

A

Something that causes the immune system to create antibodies specifically targeting that something

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2
Q

What is a cognate antigen?

A

Antigen that a given B cell’s receptors recognize

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3
Q

What is an epitope?

A

Part of the antigen that the antibody recognizes and attaches

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4
Q

What is a paratope?

A

Part of the antibody that recognizes and attaches the epitope

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5
Q

What are the 2 ways of antigen presentation?

A

MHC I and MHC II

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6
Q

What do cells do in MHC I?

A

Constantly break down proteins created within the cell (endogenous) and present them on the cell surface

  • Almost all cells of the body
  • Allows us to see what is being made inside
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7
Q

What do cells do in MHC II?

A

Eat protein (phagocytosis) outside (exogenous) the cell, break it down,and present the fragments on cell surface

  • Only antigen presenting cells can do this
  • Allows us to see what is happening outside the cell
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8
Q

Which is larger, MHC I or MHC II?

A

MHC II

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9
Q

What do MHC I and II present antigens to?

A

T cells and NK cells

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10
Q

What types of things does MHC I present?

A
  • Ordinary cellular proteins
    • Enzymes
    • Structural proteins
  • Proteins encoded by viruses
  • Parasite proteins
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11
Q

What is the normal function of proteasomes?

A

Dealing with defective proteins

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12
Q

Where are some peptides (protein fragments) brought?

A

Endoplasmic reticulum to be attached to MHC i molecules

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13
Q

What are the transport proteins in MHC I?

A

TAPI and TAP2

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14
Q

Where is the peptide-MHC I complex transported to?

A

Cell surface

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15
Q

How many MHC I genes are there, and what are they?

A 
6 (3 from each parent)
HLA-A
HLA-B
HLA-C
(Each on pairs with another protein)
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16
Q

What does the variability of MHC I molecules allow for?

A

Allows the MHC I molecules to bind many different kinds of peptides

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17
Q

Do MHC I molecules have a groove (closed at both ends) or are they open?

A

Closed-a peptide must fit in the groove

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18
Q

How long are most peptides that bind to MHC I molecules?

A

8-11 amino acids

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19
Q

Where are MHC II molecules made?

A

cytosol, injected into endoplasmic reticulum

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20
Q

What is an invariant chain protein?

A

A special protein that protects the binding area of the MHC II
Sits in the groove and stops other proteins from binding
Guide MHC II through the ER and golgi to an endosome

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21
Q

Where is the invariant chain-MHC II complex released?

A

into an endosome

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22
Q

What happens within the endosome?

A
  • Extracellular protein is broken down by enzymes (produces fragments)
  • Invariant chain protein broken down by enzymes
  • MHC II complex preserved
  • Fragments load on MHC IIs
  • MHC II peptide is transported to cell surface and displayed
23
Q

What are the 4 types of antigen presenting cells?

A
  • Activated dendritic cells
  • Activated macrophages
  • Activated B cells
  • Activated neutrophils
24
Q

Which antigen presenting cell do text books not list?

A

Activated neutrophils

25
Q

What do all antigen presenting cells have in common?

A
  • WBCs
  • Made in bone marrow
  • Must migrate out to various sites
  • Must be activated to function
  • Phagocytic
26
Q

Do MHC II have a groove (closed at both ends), or are they open?

A

Open at both ends-peptides hang over

27
Q

How long are peptides that bind to MHC IIs?

A

13-25 amino acids

28
Q

Antigen presenting cells are really what kinds of cells?

A

T cell-activating cells

present antigen to killer T cells and helper T cells

29
Q

What are 2 functions of antigen presenting cells?

A
  • Provide high levels of MHCs required for T cell activation

- Provide co-stimulatory molecules required for T cell activation

30
Q

What do activated dendritic cells do?

A

-Initiate the immune response by activating virgin T cells

31
Q

Where are sentinel cells?

A

Beneath epithelial cells

32
Q

What do dendritic cells do in their resting state?

A
  • Can take in 4x their volume of extracellular fluid per hour (take in, spit out)
  • Express some B7 (co-stimulator)
  • Not very good antigen presenting cell
33
Q

What kinds of signals activate dendritic cells?

A
  • Chemical signals (TNF, dying cells)

- Recognition of common molecular patterns

34
Q

What are toll-like receptors (TLR), and where are they?

A
  • Pattern recognition receptors

- On cell’s surface, others are inside cell, some coat inside of phagolysosomes

35
Q

What do dendritic cells do when activated?

A
  • Stay in tissue for 6 hrs
  • Eat a lot more
  • Leave through lympathics to nearest node
  • Increased MHC I and II expression
  • Increased expression of B7 co-stimulatory proteins
36
Q

B7 co-stimulatory proteins on dendritic cells attach to what protein on T cells?

A

CD28

37
Q

What is an example of cross presentation?

A

When endogenous proteins are presented on MHC II and exogenous proteins are presented on MHC I

38
Q

What do activated dendritic cells make prior to leaving the battle site?

A

Cytokines to attract monocytes

39
Q

Monocytes can become what 2 cells?

A

Macrophages and dendritic cells

40
Q

Are activated dendritic cells long or short lived?

A

Short lived

41
Q

Do activated dendritic cells kill?

A

No

42
Q

What do activated dendritic cells present antigens to?

A

Virgin T cells in lymph nodes

43
Q

Do activated macrophages travel?

A

No

44
Q

What 2 things are required for macrophages to express enough MHC and co-stimnulatory molecules to function as antigen presenting cells?

A
  1. Activation by battle cytokins (IFN-y)

2. Recognizing patterns (toll-like receptor recognition)

45
Q

What is the main function of activated macrophages?

A

Re-stimulate experienced T cells

46
Q

Activated dendritic cells activate what cells?

A

Virgin T cells

47
Q

Are virgin B cells good at making MHC II and B7?

A

No

48
Q

Virgin B cells are activated how?

A

By meeting their cognate antigen

49
Q

What are experienced activated B cells able to do?

A
  • Present antigens for helper T cells

- Able to concentrate antigen for presentation

50
Q

What makes experienced activated B cells different from other antigen presenting cells?

A

Ability to concentrate antigen for presentation

displays both BCRs with antigen and MHC II with antigen (cross linked)

51
Q

Are experienced activated B cells good at up regulating B7 and having a high affinity for their antigen?

A

Yes

52
Q

How fast are experienced activated B cells?

A

Fast-30 min

53
Q

What genes code for MHC I?

A

C6-3 genes, HLA-1 (480), HLA-2 (800), HLA-3 (260)

54
Q

What genes code for MHC II?

A

C6 HLA-D

Immunology Exam One (4 decks)

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