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Immuno > T lymphocytes > Flashcards

T lymphocytes Flashcards

1
Q

What are the three family members of the lymphocytes?

A

T
B
Natural killer

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2
Q

What is meat by the term MHC restriction, in terms of T cells?

A

T cells are restricted in what they can respond to, since they require an MHC cell to activate them

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3
Q

What are the precursors to T cells called? Where are these produced, and where do they go to mature?

A

Prothymocytes, made in bone marrow, go to Thymus to mature

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4
Q

What are the two factors that differentiate T lymphocytes?

A

Functions and surface proteins

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5
Q

Where do T lymphocytes go once they mature in the Thymus/?

A

To lymphoid organs to await activation by antigen

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6
Q

Where are memory T cells found? What do they wait for?

A

Memory T cells tend to reside in the bloodstream until directed to enter non-lymphoid tissues to elicit cell-mediated immune responses.

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7
Q

What are the two subsets of T helper cells?

A

Th1 and Th2

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8
Q

What is the response generated by Th1? Th2?

A 
Th1 = cell-mediated
Th2 = humoral immunity
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9
Q

True or false: Th1 cells are exclusive in the fact that they only direct cell mediated immunity

A

False–there are actually cytokines that Th1 cells produce that stimulate B cells to produce IgG

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10
Q

What is the role Th17 plays?

A

Inflammatory response

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11
Q

What is the function of T-follicular helper cells?

A

promote germinal center formation in lymphoid organs

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12
Q

What is the function of cytotoxic T cells?

A

Lyse virus infected cells

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13
Q

Which lymphocytes are responsible for the form of DTH by reacting to noninfectious foreign antigens in the skin and causing a contact dermatitis (like poison ivy)

A

Cytotoxic T cells

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14
Q

What are T regulatory cells?

A

Cells that secrete cytokines to inhibit immune responses, thus acting to downregulate immunity once a pathogen has been eliminated

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15
Q

What are alpha-beta T Cell Antigen Receptor?

A

the proteins on the surface of T cells that allow them to recognize and respond to antigen

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16
Q

How many specific antigens can individual T cells recognize?

A

One

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17
Q

The TCR for most T lymphocytes is comprised of what parts? What binds these parts together?

A

an alpha and beta heterodimer, bound together by disulfide bridges

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18
Q

How are different specific TCRs generated?

A

Each chain on TCRs are composed of constant and variable regions similar to immunoglobulins

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19
Q

There are two chains (alpha and beta) on each TCR. Are both involved in binding to an antigen+MHC protein, or just one?

A

Both

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20
Q

True or false: The TCR is partly responsible for MHC restriction

A

False–not at all responsible. CD4 and CD3 are.

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21
Q

What produces MHC restriction?

A

CD4 and CD8 proteins

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22
Q

The cytoplasmic tails of the TCR chains are not long enough to act as signal transducers (t-rex!!). What transduces the signal from the TCR chains then?

A

CD3 proteins

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23
Q

What are the antigen receptor for B cells?

A

Antibodies

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24
Q

How many antigen bonding sites are on TCRs? B cell surface antibodies?

A

The TCR has a single antigen binding site, whereas the B cell antigen receptor has two antigen binding sites.

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25
Q

Are B cell antibodies secreted? How about the TCR protein on T cells?

A

B cell antibodies, yes

TCR, no

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26
Q

What are CD3 proteins? Are they variable between individuals? What subtypes exits? What sites exist in the tail that allows these proteins to act as signal transducers?

A
  1. Proteins that mediate the response of TCR proteins
  2. Invariable
  3. 1 gamma, 2 epsilon, and 2 zeta
  4. Phosphorylation sites in the tails
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27
Q

Besides CD3 proteins, what other protein are needed to transduce a signal from TCR proteins?

A

Co-stimulatory molecules that stimulate their own pathway.

28
Q

What is the function of CD28? What does it bind to?

A

co-stimulator of T cells that binds to B7 on macrophages/dendritics cells/others

29
Q

What is CD40 ligand? What does it bind to?

A

Co-stimulator of T cells tha tbinds to CD40 protein on macrophages/dendritic cells

30
Q

What is the CD4 transmembrane protein? What does it do (3)?

A

Single polypeptide that is expressed on 65% of T-cells

acts in:

  1. cell adhesion
  2. Signal transduction in T-cell activation
  3. Restricts T-cell response to recognizing only class II MHC
31
Q

Besides T-cells, what other cell types have CD4 proteins? What is the consequence of this?

A

Macrophages, meaning that AIDS can target marcophages

32
Q

CD4 acts to restrict T cell responses to recognizing only class II MHC proteins. CD4 binds to non-polymorphic (i.e. invariant) regions of class II MHC proteins. Why is this important?

A

Because CD4 is invariant and wouldn’t be able to change to accommodate the many different class II MHC proteins that humans express

33
Q

Most CD8-expressing cells are what cells?

A

Cytotoxic T cells

34
Q

Structurally, CD8 is composed of what?

A

A homodimer or heterodimer

35
Q

What are the three functions of CD8 proteins?

A
  1. Cell adhesion to increase the strength of binding between CD8+ T cells and antigen-presenting cells or CTL target cells.
  2. signal transducer to aid in T cell activation.
  3. Restricts T cell regocnition to only class I MHC proteins
36
Q

When does T cell activation begin?

A

When TCR binds to an MHC-bound antigen

37
Q

True or false: Clustering of the TCR’s with multiple MHC-peptide complexes on an antigen presenting cell has been shown to be important in activating signal transduction

A

True

38
Q

Through which pathway do TCR proteins activate transcription?

A

Phospholipase C and MAP kinase cascade

39
Q

What induces transcription of IL-2 cytokine?

A

Transcription factor AP-1

40
Q

What is IL-2 cytokine?

A

provides autocrine growth of T cells by transcribing receptor and gene

41
Q

What is the result of IL-2 production in T-cells?

A

Autcrine stimulation, resulting in mitosis a crap-ton of times

42
Q

What are the two subsets of T helper cells?

A

Th1 and Th2

43
Q

What directs the production of Th1 vs Th2?

A

the presence of either interleukin-12 (IL-12) or interleukin-4 (IL-4).

44
Q

What does IL-12 do? What produces it?

A

Directs T-cells to become Th1 cells.

Macrophages/dendritic cells produce it when they see antigen

45
Q

What does IL-4 do? What produces it?

A

Directs T-cells to become Th2 cells

Not known what produces it

46
Q

T helper cells are derived from what?

A

antigen naïve CD4+ T cell precursors (called a Th0 cell),

47
Q

What is the default pathway of helper T-cell maturation?

A

Th2

48
Q

What is needed for precursors of helper T cells to be directed toward Th1 production?

A

Inflammation/macrophages etc to produce IL-12

49
Q

Peptides present in large quantities on antigen presenting cells tend to induce (???) responses, whereas those in small amounts on antigen presenting cells elicit (???) responses. (fill in the blanks)

A

Peptides present in large quantities on antigen presenting cells tend to induce Th1 responses, whereas those in small amounts on antigen presenting cells elicit Th2 responses.

50
Q

Peptides that bind strongly to the T cell antigen receptor cause (???) responses and those that bind weakly produce (???) responses.

A

Peptides that bind strongly to the T cell antigen receptor cause Th1 responses and those that bind weakly produce Th2 responses.

51
Q

What cytokine do Th1 cells produce? Th2?

A

Th1- interferon-gamma

Th2- IL-4, IL-5 and IL-13.

52
Q

What does the interferon-gamma that is produced by Th1 cells do? (2)

A
  1. activates the microbicidal activities of macrophages

2. stimulates B cells to produce IgG antibody which can opsonize microbes, thereby enhancing phagocytosis

53
Q

IL-2, together with interferon-gamma, generates what?

A

cytotoxic T lymphocytes

54
Q

Th2 cytokines promote the production of what?

A

IgE antibody, and mast cell-mediated immune reactions

55
Q

Why are immune responses generally dominated by either a Th1 or Th2 response?

A

Th1 will inhibit Th2, and vice versa

56
Q

TH17 cells develop from uncommitted naive T cells when exposed to which cytokines?

A

IL-1, IL-6 and transforming growth factor-beta (TGF-β)

57
Q

When are IL-1 and IL-6 cytokines produced? What produces them?

A

produced by dendritic cells during anti-microbial defense and are considered inflammatory cytokines

58
Q

What is the function of IL-23? What cells produce it

A

Stabilizes TH17 phenotype, produced by dendritic cells

59
Q

CTL typically have what CD protein expressed on the surface? What MHC protein does this recognize?

A

CD8+, which recognizes class I MHC proteins

60
Q

How are CTLs activated?

A

The TCR of a pre-CTL binds the peptide/class I MHC complex of a target cell, as well as CD28 (on the CTL) binding the target cell B7 costimulatory proteins

61
Q

What promotes CTLs maturation?

A

CD4+ Th1-derived interferon-gamma and IL-2

62
Q

There is evidence that CTL subsets exist that can trigger Th1 or Th2 responses. Which response is generated in the less severe form of leprosy? In the more severe form?

A

Less severe = Th1

More severe = Th2

(“They did not choose wisely”)

63
Q

What are the five steps involved in CTL killing?

A
  1. TCR- MHC class I binding
  2. CTL activation
  3. Lethal hit delivered
  4. CTL disengage
  5. Death of cell
64
Q

What are the two proteins involved in CTL killing, and what is the function of each?

A

Perforin perforates target cell, allowing for:

Granzyme B entry causes activation of Caspase pathway —>mitochondria release apoptosome

65
Q

What is the Fas ligand?

A

CTL-expressed receptor that binds to Fas protein, and activates killing

Immuno (16 decks)

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