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Micro Unit 3 > Antigen Processing > Flashcards

Antigen Processing Flashcards

1
Q

What happens if I mix an E. coli bacterium and a macrophage?

A
  1. binding
  2. engulfment
  3. Phagosome formation
    Acidification via Respiratory Burst
  4. Phagosome fuses with Lysosome to form Phagolysosome
    Digestion
  5. Membrane Disruption
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2
Q

The process of taking up a microbe, processing the antigens, and presenting it to a naïve T cell is what we refer to as

A

antigen processing and presentation.

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3
Q

Dendritic Cells

A

Phagocytic cells

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4
Q

Dendritic Cells: Minor population in the

A

blood, but:

found in skin, mucosa, lymph nodes, spleen, thymus

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5
Q

Dendritic Cells: typically express

A

MHC II molecules

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6
Q

Dendritic Cells: internalize and process

A

Ag

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7
Q

Dendritic Cells: present

A

Ag peptides within MHC II on surface

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8
Q

Dendritic Cells: important for presenting

A

Ag to T cells

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9
Q

Dendritic Cells: important for activating

A

T cells

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10
Q

Dendritic cells: PRIMARY

A

ANTIGEN-PRESENTIG CELL (Professional APC)

link between innate and adaptive immunity

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11
Q
  1. Monocytes/Macrophages: monocyte in blood —>
A

macrophage in tissue
5-10% of blood leukocytes
phagocytic cells

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12
Q
  1. Monocytes/Macrophages: characteristic
A

large nucleus

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13
Q
  1. Monocytes/Macrophages: very large
A

cell, 10 - 20 µm in diameter

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14
Q
  1. Monocytes/Macrophages: produce
A

chemotactic agents for other leukocytes

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15
Q
  1. Monocytes/Macrophages: contain arsenal of
A

lysozymes and antimicrobial proteins

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16
Q
  1. Monocytes/Macrophages: phagocytose
A

microorganisms, particles, & tumor cells

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17
Q
  1. Monocytes/Macrophages: extremely important for clearance of
A

dead cells & debris

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18
Q

Monocytes/macrophages: extremely important for

A

antigen presentation

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19
Q

B cells : a lymphocyte (part of adaptive immunity)

relatively

A

small, 6 - 10 µm in diameter

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20
Q

B cells : produce

A

chemotactic agents to attract other leukocytes

produce cytokines to activate or inactivate other leukocytes

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21
Q

B cells : can activate

A

T cells (more common in secondary (or memory) immune responses

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22
Q

Antigen presentation is a way to

A

concentrate the antigen in areas most likely to come into contact with T cells and B cells.

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23
Q

Antigen presenting cells are not limited to

A

dendritic cells, macrophages, and B cells.

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24
Q

All nucleated cells can

A

present endogenous antigens in association with MHC I molecules

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25
Q

What is the Major Histocompatability Complex (MHC)?

A
  • Original function was linked only to graft rejection

- Later found to be of critical importance to all immune responses involving protein antigens

26
Q

MHC I

A

Found on all nucleated cells
Cytoplasmic protein can be bound to MHCI
Recognized by CD8+ T cells

27
Q

MHC II

A

Found on antigen presenting cells
Extracellular proteins will be bound to MHCII
Recognized by CD4+ T cells

28
Q

MHC II

A

Found on antigen presenting cells
Extracellular proteins will be bound to MHCII
Recognized by CD4+ T cells

29
Q

Antigen processing is the processes by which antigens are

A

digested and placed on the cell surface with the correct MHC molecule.

30
Q

Two pathways of antigen processing:

A

Extracellular proteins that are internalized by professional APCs into vesicles are processed and displayed by class II MHC molecules.

Proteins in the cytosol of nucleated cells are processed and displayed by class I MHC molecules.

31
Q

Often the cytosolic proteins are

A

viral proteins.

32
Q

Virus enters into cell, process of

A

uncoating, replication, reassembly, release.

33
Q

During entry/uncoating and reassembly there are

A

viral proteins in cytoplasm.

34
Q

Proteins in the cytoplasm that are not used by the

A

cell get tagged for degradation.

35
Q

Ubiquitin binds to the

A

proteins which targets them to the proteosome.

36
Q

Step 2: Ubiquinated proteins are cleaved into

A

smaller peptides by the proteosome

37
Q

Step 3: Peptides are transported into the

A

endoplasmic reticulum through the TAP transporters (TAP stands for transporter associated with antigen processing)

38
Q

Step 4: As the peptide is being processed, Class I MHC molecule is being formed in the

A

endoplasmic reticulum.

39
Q

MHCI is unstable. Peptide binding in the binding groove will

A

stabilize the MHCI. If no peptide, the MHCI degrades

40
Q

Step 4: Peptide that is transferred into the ER by TAP is

A

trimmed to the correct size by an aminopeptidase called ERAP.

41
Q

The correct size peptide can then bind to the

A

binding groove of MHCI.

42
Q

Step 5: Once the MHCI binds to antigen, it is released from

A

ER (i.e., it is no longer bound to tapasin).
The complex is packaged into a vesicle in the Golgi.
Vesicle is trafficked to the cell surface, fused with the cell membrane resulting in expression of MHCI+Ag

43
Q

The antigen bound to MHCI can be a

A

foreign protein/peptide or it can be a self peptide (i.e., from a protein from the host cell). This is one way in which the immune system is supposed to recognize self vs. non-self.

44
Q

Antigen presentation bridges antigen recognition by

A

innate immune system to the activation of the adaptive immune system.

45
Q

Antigen presentation is necessary for

A

T cell-mediated killing, and augments antibody production by B cells.

46
Q

Antigen presentation is

A

context dependent, allowing the deployment of appropriate immune responses under different conditions.

47
Q

CD8+ T cells are

A

MHC I restricted and recognize cytosolic proteins

48
Q

CD4+ T cells are

A

MHC II restricted and recognize extracellular and intravesicular pathogens

49
Q

Multiple receptors on T cells need to be engaged in order to

A

activate the T cell. Recognition of antigen is not enough.

50
Q

The T cell receptor (TCR) recognizes antigen, but it does not

A

signal.

51
Q

CD3 and z are non-covalently associated to the

A

TCR
Expression of the TCR, CD3 and z chain are required for antigen recognition and signalling
TCR recognizes Ag
CD3 and z signal

52
Q

Recognition of antigen (and MHC molecule) in the absence of

A

co-stimulation fails to activate the T cell. In fact, it leads to anergy of the T cell.

53
Q

Multiple receptors on T cells need to be engaged in order to activate the T cell. Recognition of antigen is not enough.

A

TCR recognizing antigen
CD4 recognizing MHCII
CD28 on T cell recognizing B7 molecules on APC
LFA-1 on T cell recognizing ICAM-1 on APC

Together they are referred to as the immunological synapse

54
Q

Self/Non-self vs. danger

A

Bacterial products such as those in the adjuvant stimulate the expression of MHC, adhesion molecules, and co-stimulatory molecules in APCs

These signals provide T cells with “context” information that may determine the modality of their responses, e,g., tolerance, TH1, or TH2 response

55
Q

Function of co-stimulatory molecules

: Absence of

A

co-stimulatory molecules, T cell will not be activated (anergy)

56
Q

Function of co-stimulatory molecules

Absence of antigen-TCR interaction, T cell will not be

A

stimulated.

57
Q

Function of co-stimulatory molecules

Co-reception of

A

both signals activate T cells

58
Q

Function of co-stimulatory molecules

At the termination of the

A

immune response, CTLA-4 replaces CD28 and downregulates T cell function

59
Q

B7 Receptors Play a Role in

A

Activating T cells AND Terminating the T cell Response!!

60
Q

A. CTLA-4 can competitively inhibit

A

CD28 binding to B7

61
Q

B. CTLA-4, when bound to B7, will actively

A

block signals from the TCR and from CD28

Micro Unit 3 (6 decks)

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