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Immunology > T Cell Mediated Immunity > Flashcards

T Cell Mediated Immunity Flashcards

1
Q

What is anergy?

A

nonresponsiveness to Ag under optimal conditions of stimulation

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2
Q

What is CTLA-4?

A

high affinity B7 receptor critical for shutting of T cell response

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3
Q

What are granzymes? What cells are they secreted by?

A

serine proteases in cytotoxic T cells involved in inducing apoptosis in target cells

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4
Q

What is produced by activated naive T cells to further proliferation and differentiation?

A

IL-2

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5
Q

Why are integrins important for T cell development?

A

They strengthen the adhesion with APCS, and T cells must adhere to APC for 6-12 hours to be activated.

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6
Q

What controls routes of T cell migration?

A

selectins, integrins, chemokines

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7
Q

What does T cell initially bind through? Is it high or low affinity? Does binding induce change?

A

LFA-1 on T cell binds with low affinity to ICAM-1 on APC. Binding of T cell signals conformational change of LFA-1 to increase affinity and prolong contact

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8
Q

What are the two requirements for activating naive T cells?

A

Ag recognition and costimulation by substance released during innate immune response to microbe, which indicates that the microbe is immunogenic as well as antigenic

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9
Q

How do adjuvants work?

A

Bacteria (immunogenic) and nonbacterial (nonimmunogenic) protein presented together. This stimulates the APC to deliver costimulation and T cells recognize the nonbacterial Ag, proliferate and differentitate specific for nonbacterial protein

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10
Q

How do you get peripheral tolerance?

A

Induce anergy in cells by presenting Ag without costimulatory CD28 signals.

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11
Q

When is B7-2 the major ligand for CD28? B7-1?

A

B7-2 expression is constitutive and induced faster upon stimulation, so initially is the major ligand. B7-1 expressed later and sustains T-cell activation.

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12
Q

What T cells don’t express CD28?

A

CD8 T cells, gamma-delta T cells, memory and effector T cells

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13
Q

When do you not require costimulation?

A

If the signal is strong enough, CD28 costimulation isn’t needed (i.e. for some high avidity responses to viruses)

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14
Q

Which Thelper cell is involved in CMI? What is its effector action?

A

Th1 cell, activates infected macrophages

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15
Q

Which Thelper cell is involved in humoral immunity? What is its effector action?

A

Th2 cell, activates specific B cell to make Ab

Th1 cell, induces B cells to produce opsonizing Ab

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16
Q

What cytokines do activated Th1 cells release?

A

IFNgamma and CD40L- activates macrophage
FasL or TNFb- kills chronically infected cells so activated macrophages can phagocytose bacteria
IL-2- induces Tcell proliferation
IL3 and GM-CSF- induces macrophage differentiation in BM
TNFa and TNFb- activates epithelium to let new macrophages get to site of infection
CCL2- chemoattractant for macrophages

17
Q

What does Th2 release that inhibits Th1 response?

A

IL-10

18
Q

What does Th1 release that inhibits Th2 response?

A

IFN gamma

19
Q

What do CD8 T cells use as effector molecules?

A

perforin, granzymes, granulysin, Fas ligand, IFN gamma, TNFa, and TNFb

20
Q

How do CD4 T cells help CD8 T cells?

A

IL-2 produced by Th1 cells

21
Q

What are the 3 killing mechanisms of CTLs?

A
  1. granule exocytosis (granzymes, perforin- fast killing)
  2. cell surface TNF-family effector molecules expressed (slow killing)
  3. Secretion of soluble toxic cytokines (TNF, IFN- slow killing)
22
Q

How does granzyme B act?

A
  • Cleaves procaspase to activate caspase, which causes DNA fragmentation
  • mitochondrial damage causes cytochrome C release and apoptosis
23
Q

Why don’t release lytic granules kill CTL?

A
  • Cathepsin B in the vesicle fuses with the membrane to protect CTL after degranulation/exocytosis
  • Proteinase inhibitor 9 (serpin) that inhibits granzyme B is expressed by CTL
24
Q

What signals production of CTLA-4?

A

Crosslinking of CD28 delivers costimulatory signal for activation of naive T cells and induces CTLA-4 expression

25
Q

What does a CTLA-4 deficiency cause?

A

death, can’t shut off immune response and lymphocyte build up drowns mice

26
Q

Name 4 mechanisms to shut off immune response.

A
  1. eliminate Ag
  2. eliminate other signals (APCs)
  3. IL-2/IL-2 receptor signals via Tregs
  4. kill with immunoregulatory cells (Fas-FasL)
27
Q

Why do Tregs rely on IL-2 to shut off immune response?

A

Need IL-2 for T cell development to get Tregs, if knocked out, will get same presentation as CTLA-4 knockout

Immunology (18 decks)

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