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Microbiology & Immunology (Fall 2023) > T Cell Immunity Part 2 > Flashcards

T Cell Immunity Part 2 Flashcards

1
Q

How are memory cells determined to be helper or cytotoxic T cells?

A

Predestined by memory cells which remain after infection is resolved

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2
Q

What do T cells do after they are activated in SLT?

A

Naive T cells enter SLT in search for their respective antigens/pathogens

T cell activation

Effector T cells leave the SLT and enter the infected tissue (from innate signaling to either kill (ctl) or “help”(Th1) control infection

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3
Q

Where do antigen presenting cells receive the antigen (peptide)

A

At site of infection, antigen is cut from infected cell

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4
Q

How are SLT specialized?

A

To facilitate interaction of circulating T and B lymphocytes with antigen (highly compartmentalized)

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5
Q

What is the process of T cell activation?

A
  1. Antigen comes in the lymph (either free antigen or bound/presented on dendritic cells)

2.in t cell zones of lymph node name T cells can recognize antigen on the surface of dendritic cells

  1. Effector t-cells leave the lymph node to travel to infected tissue
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6
Q

What is the role of antigen presenting cell?

A
  • initiates adaptive response
  • processes pathogens and express their antigens on surface on MHC I or II
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7
Q

What are the 3 types of antigen presenting cells?

A
  1. dendritic cells
  2. macrophages
  3. b cells
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8
Q

How does antigen uptake occur in dendritic cells?

A

macropinocytosis and phagocytosis by tissue dendritic cells

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9
Q

What is the MHC expression on dendritic cells?

A

low on immature dendritic cells, high on dendritic cels in lymphoid tissues

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10
Q

Where are dendritic cells present

A

everywhere throughout the body

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11
Q

What effect do dendritic cells have?

A

result In naive T cell activation

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12
Q

How does antigen uptake occur in macrophages?

A

macropinocytosis and phagocytosis

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13
Q

What is the MHC expression on macrophages?

A

inducible by bacteria and cytokines

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14
Q

Where are macrophages found?

A

lymphoid tissue, connective tissue, body cavities

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15
Q

What is the effect of macrophages?

A

results in activation of macrophages by effector and memory T cells

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16
Q

How does antigen uptake occur in B cells?

A

antigen-specific receptor

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17
Q

What is the MHC expression by B cells?

A

constitutive increases on activation

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18
Q

Where are B cells found?

A

lymphoid tissue and peripheral blood

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19
Q

What is the effect of B cells?

A

results in deliver =y of help to B cells by T(FH) cells

20
Q

What is macropinocytosis?

A

collects fluids and antigens

21
Q

What is endocytosis?

A

another way to bring things from outside to inside by b cells

22
Q

What is the role and function of dendritic cells dependent on?

A

maturation

immature: highly phagocytic (professional phagocytes) for innate immunity

mature: loses phagocytic abilities but can present antigen to T cells so it initials adaptive immunity

23
Q

How do dendritic cells mature?

A
  1. immature dendritic cells reside in peripheral tissues
  2. dendritic cells migrate and mature via lymphatic vessels to lymph nodes
  3. mature dendritic cells activate naive T cells in lymphoid organs
24
Q

What are the 3 ways of bringing in pathogens from dendritic cells?

A
  1. receptor-mediated phagocytosis
  2. macropinocytosis
  3. viral infection
25
What type of pathogen is up took during receptor mediated phagocytosis for dendritic cells? Which MHC molecules are loaded? What type of naive cell is activated?
extracellular batteria and fungi by MHC class II, activating CD4 T cells
26
What type of pathogen is up took during macropinocytosis for dendritic cells? Which MHC molecules are loaded? What type of naive cell is activated?
extracellular bacteria, soluble antigens, virus particles by MHC class II, activating CD4 T cells
27
What type of pathogen is up took during viral infection for dendritic cells? Which MHC molecules are loaded? What type of naive cell is activated?
viruses by MHC class I, activating CD8 T cells
28
How is the site of infection located?
citokines
29
What do dendritic cells do in SLT?
1. antigen presentation 2. trigger clonal expansion 3. CD4+ gives rise to helper T cells (exogenous peptide) 4. CD8+ gives rise to cytotoxic T cells (endogenous peptide)
30
What does T cell activation induce?
metabolic changes that prepare the T cell for rapid clonal expansion and differentiation
31
What are the 3 signals of T cell activation?
1. TCR binding to antigen/MHC 2. Cosimulatory receptors 3. Cytokine signalling
32
What occurs when there is a lack of cosimulatory receptor (there is a non-APC cell)? Why is this a good checkpoint?
fails to activate T cell (anergic) so the T cell continues through circulation without activity stops autoreactive T cells
33
What is the role of a cytotoxic effector T-cell?
- triggers apoptosis for escaped phagocytosis - recognizes complex of endogenous peptide with MHC class I and kills infected cell
34
What is the role of a helper T cell (Th1)?
- recognizes complex of exogenous peptide with MHC class II and activates macrophage
35
What is the mechanism for cytotoxic T-cells to trigger apoptosis?
1. CTL attaches to infect cell on MHC class I 2. releases perforin and granzymes 3. induction of exocytosis (granules fuse with the cytotoxic T cell membrane and perforin is released) 4. perforin inserts in the membrane, polymerizes, and forms cylindrical pores 5. granzyme initiates a cascade of reactions that results in the fragmentation of target cell DNA and viral DNA
36
Why is it important to rapidly induce DNA franmentation after CTL contact?
precent viral replication and assembly which the target cell s destroyed
37
What os the role of perforin?
aids in delivering contents of granules into cytoplasm of target cell by making pores in infected cell
38
What is the role of granzymes?
serine proteases which activate apoptosis once in the cytoplasm of the target cell
39
What cells use granules to trigger apoptosis?
cytotoxic T cells and nk cells (innate immunity) which is why they are in the same branch from lymphatic progenitors
40
What does CTL do after it triggers apoptosis in an infected cell?
surveys tissue for signal and moves onto next target cell
41
What is the full cycle of immune system response in a viral infection?
1. IFN-alpha and IFN-beta are produced first after viral infection 2. cytokine release, a wave of NK cells follow 3. virus is eliminated when virus specific T cells apoptose
42
What is the role of Th1 helper t-cells?
activates macrophages
43
What is the mechanism of Th1 helper T cells in activating macrophages?
1. bacterium is inside cell in a vesicle (and is potentially stops lysosome from fusing) 2. Th1 binds to MHC class II complex in the macrophage 3. Th1 secretes IFN-gamma which activates macrophages 4. lysosome fuses with vesicle In cell
44
How do helper T-cells contain intracellular pathogens?
- if intracellular pathogen can't be completely cleared, helper T cells for a barricade around infected macrophages into a GRANULOMA which prevents infection to other cells
45
What is SCID? (severe combined immune deficiency)
- absence of functional T cells (so no B cell activation) causing rapid infection with opportunistic pathogens
46
What is AIDS (acquired immune deficiency syndrome? What does the infection rate depend on? What is symptoms and the treatment?
human immunodeficiency virus infection rate depends on route of contact (blood contact is highest) and the amount of virus contained in the bodily fluid CD4+ T cells start to decrease. Frequent opportunistic pathogen infections no cure or vaccine, and treatment is through antiretroviral therapy
47
What are type 1 interferons?
IFN-alpha and IFN-beta which are signals for NK cells

Microbiology & Immunology (Fall 2023) (8 decks)

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