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Veterinary Immunology > Lecture 8- T Cell Response to Antigen > Flashcards

Lecture 8- T Cell Response to Antigen Flashcards

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1
Q

What do T helper (CD4) cells do?

A
  • Monitor the body for extracellular microbial infections
  • Activate/stimulate other immune cells to fight infection (especially B cells & macrophages)
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2
Q

What do Cytotoxic T-cells (CD8) do?

A

destroy host cells infected with intracellular microbes
- destroy tumor cells

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3
Q

What are the 2 types of Dendritic cells and what are their functions?

A
  • Regular: present Ag to helper and cytotoxic T cells
  • Follicular: Trap Ags for B cells
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4
Q

Naive T helper cells only respond to:

A

Antigens presented by dendritic cells in the primary immune response
Co-stimulation

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5
Q

Where are immature dendritic cells located and what do they do?

A
  • in tissues (epithelial and mucosa)
  • capture Ags, trap and internalize them

(they migrate to the lymph node, are drained by lymph secretion then are matured)

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6
Q

Where are mature dendritic cells located and what do they do?

A
  • lymph nodes
  • present Ags to T cells
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7
Q

What are Langerhans cells?

A

dendritic cells of the skin

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8
Q

Helper T cells typically begin as _____.

A

Th-0 (Th-O?)

differentiate depending on cytokines from APC and in the environment

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9
Q

What are the different type of T helper cell differentiations?

A
  • Th1
  • Th2
  • Th17
  • T regulatory cells (Treg)
  • small number become memory cells

+ TFH (follicular helper)

[he doesn’t mention TFH in text but it’s in a photo]

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10
Q

Stimulated/primed Th cells first secrete ______.

A

IL-2
(T cells growth factor, exerts both an autocrine and paracrine effect)
[self activating]

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11
Q

What is the function of T γδ lymphocytes?

A

To respond to mucosal pathogens

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12
Q

Dendritic cells detect:

A

PRRs (pathogen recognition receptors) & cytokines secreted by other cells at infection site

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13
Q

What do T helper cells produce?

A

CD40 ligand & cytokines

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14
Q

What are the 4 steps in dendritic function?

A

1 - recognize antigen is present
2 - travel/migrate to lymph node
3 - activate naive T cell w/ aid from co-stimulatory molecules
4 - cytokines detected by DC → dictate what Th-cell should proliferate

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15
Q

Differentiation into Th1 is influenced by ____.

A
  • IL-12 (secreted by APCs)
  • IFN-γ (secreted by activated NK cells and Th cells themselves)
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16
Q

What does CD40 ligand do?

A
  • binds to the CD40R on an APC
  • Causes the APC to produce more MHC 2 and B7 (co-stimuilatory receptors for rhe T-cells)
  • higher frequency of APC-induced T cell activation
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17
Q

Differentiation into Th2 cells is influenced by ____.

A

IL-4 (secreted by other Th2 cells and mast cells)

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18
Q

What 4 things does Th1 secrete?

A
  • IL-2
  • IL-12
  • IFN-γ
  • TNF
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19
Q

What is IFN-γ (interferon gamma) ?

A

potent macrophage activator
- stimulates activated B cells
- stimulates Th-cell differentiation
- stimulates CD8 into CTL

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20
Q

What does TNF (Tumor necrosis factor) do?

A
  • activates vascular endothelium expression of adhesion molecules
  • aids in WBC recruitment
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21
Q

What is the main function of Th1?

A

to aid macrophages in fighting intracellular infections [bacteria & protozoa]

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22
Q

What are the main effector cells of Th1 immunity?

A
  • Macrophages → enhance phagocytic activity : mediated by IFN-γ
  • PMNs
  • CD8 → stimulated to differentiate into Cytotoxic lymphocytes [CTLs]
  • NK cells
  • IgG B cells → opsonizing & complement fixing
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23
Q

What 5 ILs does Th2 secrete?

A
  • IL-4
  • IL-5
  • IL-9
  • IL-10
  • IL-13
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24
Q

What does IL-4 do?

A
  • Stimulates proliferation of primed B cells
  • High levels promote IgE class-switching → allergic reactions mediated by IgE

4 y/o is allergic to prime and bees. That’s all that is in his classroom, so he has to switch

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25
What does IL-5 do?
- Stimulates B cell differentiation into plasma cells - High levels activate eosinophils & mast cells → act against helminths - facilitates class-switching to IgA → w/ aid from TGF-B & BAFF cytokines
26
What does IL-13 do?
Increases mucus production & peristalsis in intestine
27
What are the main effector cells of Th2?
- B cells - Eosinophils - Mast cells - Basophils
28
What is Th2 responsible for?
Humoral immune system and allergic reactions (because it hosts the immunity effectors against extracellular parasites)
29
What does Th17 secrete?
- IL-17 - IL-21 - IL-22 - IL-23
30
What does IL-17 do?
recruits neutrophils to infection sight
31
What does IL-21 do?
stimulates B cells to produce IgG & IgA → guard mucosa
32
What does IL-22 do?
stimulates epithelial cells to produce antimicrobial peptides → resist microbial invasion
33
What does IL-23 do?
growth factor for other Th-cell to differentiate into Th17
34
What is the main function of Th17?
aid immune response to fungi & extracellular bacteria
35
Differentiation into Th17 cells is influenced by:
- APCs secrete IL-6 - Cytokines from Dendritic cells balance Treg & Th-17 differentiation TGF-B, IL-6, IL-23
36
Differentiation into Treg or Reg-Th cells is influenced by:
- Cytokines from Dendritic cells balance Treg & Th-17 differentiation - Once pathogen is eradicated
37
What does Treg secrete?
- IL-10 - TGF-B
38
What does IL-10 do?
suppresses macrophage function & reduces APC-B7 expression CTLA-4 (Cytotoxic T-Lymphocyte-Associated Protein 4) binds to remaining B7 on APC = further lower TCR-APC stimulation
39
What does TGF-B do?
induces generation of more Treg & reduces CTL attack
40
What is the main function of Treg/ Reg Th?
Suppress immune response & prevents autoimmunity
41
What is PD-1?
Programmed deadth-1 - Appears on the surfaces of cells under attack
42
What does PD-1 bind to?
Effector T cells that are working AFTER infection is over - Those effector cells become lethargic & non-functioning → stopped by PD-1 binding
43
What does IL-1 do?
- Increases vascular permeability which is how cells move through the endothelium to where they are needed in the tissues - Stimulates the production of IL-6
44
What does IL-2 do?
Proliferation and differentiation of T-cells into effector cells
45
What does IL-6 do?
- Acts on the liver to produce acute phase proteins leading to inflammation
46
What does IL-8 do?
- Attracts and activates neutrophils - also helps to increase vascular permeability
47
What does IL-12 do?
- Activates Natural Killer (NK) cells - Induces lymphocyte differentiation
48
IFN-γ is secreted by _______.
NK cells and T-helper cells - important in inhibiting viral replication
49
What is BAFF?
B-cell activating factor
50
What is TNF?
tumor necrosis factor
51
What is PMNs?
polymorphonuclear lymphocytes → neutrophils
52
What is LFA-1?
leukocyte function-associated antigen-1 - integrin/adhesion molecule that helps dock the T cell to the APC
53
What do CD8/ Tc cells recognize?
antigens displayed by MCH-1 on host cells and cross-presented on dendritic cells - Intracellular antigens - Tumor antigens
54
Tc cells may require ____ from activated T helper cells
co-stimulation via cytokines
55
Stimulated Tc cells proliferate and differentiate into ____.
Cytotoxic T-lymphatic cells (CTLs)
56
What occurs after signal transduction of Tc cells? (secreting proteins & create pores in the membranes of the infected cells)
- The release of CTL granules at point of contact w/ the targeted host cells - Granzymes & perforin (Receptor-mediated endocytosis)
57
What is the Fas-ligand?
death-inducing receptor - engagement activates caspases (induce apoptosis)
58
What are the effector functions of CTLs?
- granzymes - perforin - Fas-ligand
59
What does perforin do?
- Inserts into endosomal membranes - Facilitates movement of granzymes into cytoplasm
60
What do Granzymes do?
(Enzyme) Activate caspase present in target cell → systems within the cell that control cell death & inflammation
61
When do memory T cells exist?
after the infection is eradicated
62
What are 5 features of memory T cells?
- Long-lived - Present in lymphoid organs, mucosal tissues & circulation - Functionally inactive - Require IL-7 to remain alive - Rapidly respond to repeat exposure to same pathogen
63
What is the first signal for naive T-cell activation?
- CR binds to specific antigen displayed by MHC 2 - CD4 co-receptor binds to MHC 2
64
What are the second signals for a naive T-cell to be activated? (co-stimulation)
- CD28 binds to B7 [on APC] - Absence of co-stimulation → T cell remain in state of anergy [unresponsiveness] & undergoes apoptosis
65
CD28 binds to ____.
B7 on APC
66
What is the third event for naive T-cell activation?
clustering of TCR & co-receptors - Formation of an immunologic synapse - CD3 complexes → transduce signals to interior of Th-cell
67
LFA-1 [CD11] binds to _____ [on APC]
ICAM (Leukocyte function-associated antigen-1)
68
CD40L [CD154] binds to _____[on APC]
CD40 - Activates APC to express more B7 molecules - Activates secretion of IL-12 by APC
69
Gamma-delta T-cells are important in _______.
mucosal surfaces
70
Gamma-delta T-cells respond to:
- Cell surface antigen w/o processing & presentation on MHC → NO MHC restriction - Stress proteins expressed on atypical class Ib MHC molecules, may be CD8
71
What are responses of Gamma-delta T-cells?
Secrete cytokines Simulates Cytotoxic

Veterinary Immunology (15 decks)

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