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Micro and Immuno > T Cell Function > Flashcards

T Cell Function Flashcards

1
Q

How are T cells contributing to the pathogenesis of periodontitis?

A

…

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2
Q

What are the two types of cell-mediated immunity?

A
  1. CD4 helper T cells produce cytokines that activate and recruit other cells
  2. CD8 cytotoxic T cells kill infected cells with microbes in cytoplasm
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3
Q

Th1 cells

A

S subset of CD4 T cells; initiate inflammation and immunity by activating macrophages by secreting interferon gamma

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4
Q

Th17 cell

A

A subset of CD4 T cells that are characterized by production of the cytokine IL-17. They help recruit neutrophils to sites of infection.

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5
Q

describe the discovery of cell-mediated immunity

A
  • Experiment showing transferable from immune animals to naive animals by T cells but not serum
  • bacteria were killed in vitro by activated macrophages not T cells
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6
Q

How do helper T cells develop and mediate their function? (overview)

A

Different cytokines are involved

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7
Q

How is the recognition of antigen by T cell receptor very specific?

A

T cell clones express TCR that can only recognize one peptide/MHC complex

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8
Q

Though TCR are very specific, presentation of antigen to T cells by APCs is very ___

A

diverse

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9
Q

How is the presentation of antigen to T cells by APC very diverse?

A
  • several peptides can be presented by different MHC I and MHC II molecules on the surface of the same dendritic cell
  • T cells patrol LN in search of DC with the perfect fit
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10
Q

Give the characteristics of CD4 helper T cell subsets

A

Th1: make IFNgamma and activate macrophages. This targets intracellular pathogens.

Th2: make IL4, IL5, and IL13 and activate eosinophils. This targets parasites (helminths) through IgE

Th17: make IL17 and IL22 and activate neutrophils. This targets extracellular pathogens.

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11
Q

describe the development of T helper effector cells

A
  • different cytokines are produced by DC or other innate cells that have recognized different types of microbes
  • the cytokines induce different transcription factors
  • transcription factors determine the fate of the helper T cells
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12
Q

development of Th1 cell

A
  1. intracellular microbe discovered
  2. dendritic cell releases IL-12 cytokine, NK cell releases IFN-gamma cytokine
  3. T cell now antigen-activated and expresses transcription factors T-bet, STAT4, and STAT1
  4. Th1 cell formed
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13
Q

development of Th2 cell

A
  1. helminth (parasite) discovered
  2. dendritic cell and mast cells and eosinophils involved, release cytokine IL-4
  3. T cell now antigen-activated and expresses transcription factors GATA-3 and STAT6
  4. Th2 cell formed
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14
Q

development of Th17 cell

A
  1. extracellular fungi or bacteria discovered
  2. dendritic cell involved, releases cytokines IL-1, IL-6, IL-23, and TGF-beta
  3. T cell now antigen activated and expresses transcription factors ROR-gt and STAT3
  4. Th17 cell formed
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15
Q

Function of Th1 cells

A

Secrete IGNgamma to induce macrophages to kill ingested microbes in classical macrophage activation (enhanced microbial killing)

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16
Q

how are macrophages activated by Th1 cells?

A
  • involves CD40L (on CD4 cell) and CD40 (expressed on APCs - macrophage, dendritic cell, B cells)
  • involves IFNgamma secreted by CD4 cell and IFNgamma receptor
  • macrophages produce cytokines, up-regulate MHC, costimulatory molecules, and microbicidal activities
17
Q

what is the response of macrophage activated by Th1 cells?

A
  • secretion of cytokines TNF, IL-1, IL-12, chemokines
  • increased expression of MHC and costimulators (B7 molecules)
  • killing of phagocytosed bacteria
18
Q

Function of Th2 cells

A
  • IL4 induces B cells to produce IgE
  • IL5 induces eosinophil activation
  • mediates worm elimination, mast cell degranulation, intestinal mucus secretion and peristalsis, and alternative macrophage activation (enhance fibrosis/tissue repair)
19
Q

compare classical and alternative macrophage activation

A

M1: killing (by ROS, NO, and lysosomal enzymes) and inflammation

M2: tissue repair and inhibit inflammation (happens at end of immune response)

20
Q

what triggers a monocyte to differentiate into an M2?

A

IL-13 and IL-4

21
Q

what triggers a monocyte to differentiate into an M1?

A

Microbial TLR-ligans, IFNgamma

22
Q

Functions of TH17 cells

A
  • IL17 mediate recruitment of neutrophil via induction of cytokines/chemokines production from other cells
  • IL22 mediates antimicrobial peptides and increased barrier integrity through epithelial cells
  • important for extracellular microbes
23
Q

functions of Tfh cells

A
  • found in the B cell zone
  • make IL21 which mediates production of Ig (immunoglobulin) by B cells
24
Q

How do cytotoxic T cells mediate their function? (overview)

A

Recognition of antigens and killing via perforin and granzyme FasL

25
Q

cytotoxic cells of the innate immune response

A

NK

26
Q

cytotoxic cells of the adaptive immune response

A

CD8 T cells

27
Q

describe the killing by CD8 CTL

A
  • antigen recognition and binding of CTL to target cells: CTL binds to target cells via ICAM-1 (target cells)–LFA-1 (CD8 cell) interaction
  • Perforin and granzyme released from granules mediates killing: perforin facilitates entry of granzymes into the cytosol, grandames activate apoptosis
28
Q

Describe FasL-mediated killing by CD8 CTL

A
  • activated CTL express FasL
  • FasL binds to Fas on target cells and induces cell death
  • minor role in killing (homeostasis - perforin and granzyme major killers)
29
Q

describe the cooperation between Th1 cells, CD8 cells, and macrophages in killing intracellular bacteria

A
  • Th1 cells activate macrophage using IFNg to lyse intravesicular microbes
  • CD8 kill infected cells with the help from Th1 cells (for cases when microbe is in the cytoplasm and not the phagolysosome)
30
Q

describe the response of CD8 cells to acute or chronic viral infection

A
  • acute infection induces a protective response; memory T cells form in case re-infected
  • chronic infection induces expression of inhibitory molecules and leads to exhaustion
31
Q

How do Th17 cells play a role in periodontitis?

A
  • Th17 contribute to the inflammation through IL-17 (inflammation already present with neutrophils)
  • Th17 induce fibroblasts to produce G-CSF (further neutrophil recruitment and granulopoeisis and mobilization in the bone)
  • G-CSF recruit more neutrophils

Micro and Immuno (17 decks)

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