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Molecular Immunology > L7-Exam 2 > Flashcards

L7-Exam 2 Flashcards

1
Q

The ___ is an absolute requirement for the maturation and differentiation of mature T cells

A

Thymus

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2
Q

Children born without a thymus (DiGeorge’s Syndrome) do not have ______

A

mature T cells

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3
Q

T cell differentiation occurs throughout life , but will tapper off subsequent to ___ as the thymus decreases in size (known as: thymic involution)

A

puberty

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4
Q

The___ is the site of education of a T cell and is the primary lymphoid organ for development of T cells; it is analogous to the bone marrow as the primary organs for development of B cells

A

The thymus

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5
Q

What three things occurs to a T cell when it is in the thymus?

A

1) Acquires T cell antigen receptor (TCR) - antigen specificity
2) Learns tolerance of self
3) Learns self-HLA restriction (recognition of foreign peptide only in association with self HLA molecules)

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6
Q

True or False: A common lymphoid progenitor stem cell leaves the bone marrow, without any T cell features. It could not be distinguished from a pro-B cell.

A

True

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7
Q

True or False: when T lymphocytes are in the bone marrow, they contain chemokine receptors on their surface

A

True

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8
Q

The precursor stem cells enter the thymus at the cortical-medullary junction and then migrate to the cortex. At this time, they are called ______ cells.

A

Double Negative Cells

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9
Q

True or False: Double negative cells expressed both CD4+ and CD8+

A

False - double negative cells express neither CD4+ nor CD8+

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10
Q

The decision whether to be an alpha-beta or gamma-delta T cell occurs at the ___ stage

A

Double Negative

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11
Q

Shortly after becoming DN cells, the cells begin expressing the genes for ___ and ___

A

RAG-1 and RAG-2

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12
Q

What is the function of RAG-1 and RAG-2?

A

Responsible for randomly rearranging genes that encode the delta/gamma and alpha/beta chains of the T cell antigen receptor (TCR)

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13
Q

The DN cells that become delta-gamma T cells express what three proteins on their cell surface?

A

CD3+
TCR gamma
TCR delta

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14
Q

True or False: The DN cells that become γδ T cells leave the thymus and migrate to epithelial sites around the body

A

True

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15
Q

If a DN cell does not become a delta-gamma T cell, it will be come a ____, which expresses what four proteins on its cell surface?

A

Pre-aßT cell (pre-T cell)
1. CD3+
2. Pre-Ta
3. TCRß
4. Zeta

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16
Q

True or False: γδ T cells continue to differentiate within the thymic cortex

A

False -Pre-aßT cell (pre-T cell) continue to differentiate within the thymic cortex

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17
Q

The functioning of the pre-T cell receptor results in ___ signals that stop further re-arrangement of the __ chain and initiates rearrangement of the __ chain

A

intracellular; beta; alpha

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18
Q

What five proteins do double positive cells of the thymus cortex express on their surface?

A

1) CD3+
2) CD4+
3) CD8+
4) TCRa
5) TCRβ

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19
Q

As maturing double positive thymocytes filter through the thymic cortex, they must pass through a mesh of stromal cells, known as:
1)
2)

A

1) thymic epithelial cells
2) interdigitating thymic dendritic cells

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20
Q

Double positive CD4+ and CD8+ thymocytes undergo selection, which is mediated by interactions with HLA molecules on ___ cells and CD4 and CD8 molecules on ___

A

stromal cells; thymocytes

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21
Q

_____ are among the few cells the express both class of HLA molecules (class I and II) constitutively

A

Thymic epithelium

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22
Q

During ___ selection, thymocytes must bind with a certain critical affinity to HLA molecules on the thymic epithelium.

A

positive

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23
Q

Once a cell completes positive selection, the cells are now educated to self HLA molecules, meaning they will only responds to….?

And the are considered to be ___-restricted

A

Self HLA + processed antigen (self or foreign)

HLA-restricted

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24
Q

____ selection occurs during transition from thymic cortex to thymic medulla, when encounter interdigitating dendritic cells at CM junction and later when they interact with medullary epithelial cells

A

Negative selection

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25
Q

Since T cells that survive positive selection are potentially able to respond to peptides derived from both self and foreign molecules loaded into the MHC, allowing those cells to leave the thymus and enter the circulation could result in ___

A

autoimmunity

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26
Q

If developing T cells responds to MHC + self peptide at the stage of negative selection, the cells die via ______

A

central tolerance mechanisms

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27
Q

The process of negative selection weeds out self-reactive cells via ___ or by inducing ___. The surviving cells are said to be ____

A

apoptosis; inducing T cell anergy
self-tolerant

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28
Q

____ immature thymocytes must bind HLA Class I and II on thymic epithelial cells with “just the right affinity.” If they don’t, they undergo apoptosis and die

A

CD4+/CD8+

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29
Q

Tolerance learned during ontogeny is called ____

A

central tolerance

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30
Q

Antigens present in the thymus are almost always ___ antigens

A

self

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31
Q

True or False: In Central T Lymphocyte tolerance, strong recognition to antigens results in apoptosis

A

True

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32
Q

Central T Lymphocyte Tolerance involves immature, ____ T cells

A

Double positive

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33
Q

True or False: The cells that survive both positive and negative selection become either CD8+ or CD4+

A

True

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34
Q

What are four features of cells that have survived positive and negative selection?

A

1) alpha/beta TCR+, CD3+, and CD4+
(or: alpha/beta TCR+, CD3+, and CD8+)
2) self-HLA restricted
3) self-tolerant
4) foreign antigen specific (HLA + foreign peptide specific)

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35
Q

If they survive the positive and negative selection process in the thymus, a mature, naiive T cell will leave the thymus and enter the circulation via the ____ and ____

A

blood; secondary lymphoid organs

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36
Q

What population of T cells leave the thymus for epithelial sites without undergoing positive and negative selection?

A

T cells that have the γδ TCR

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37
Q

Stem cells migrating to the thymus express this/these molecules on their surface
A. CD3
B. CD3, CD4, and CD8
C. CD4 and CD8
D. Chemokine receptors
E. Chemokine receptors and CD3

A

D. Chemokine receptors

38
Q

True or False: Recirculation increases the change that a lymphocytes will encounter its antigen

A

True

39
Q

Specific receptor-ligand interactions between ____ and _____cells occurs that mediate ___ and homing of the lymphocyte

A

lymphocytes and endothelial cells; recirculation

40
Q

If, while filtering through a lymph node, a T cell encounter an APC (dendritic cell or B cell) expressing HLA+foreign peptide, it may respond (___) or not responds (___)

A

respond = activation
not respond = tolerance

41
Q

T lymphocytes respond only to processed protein antigens derived from what three pathways?

A

-Endosomal
-Phagosomal
-Cytosolic (exogenous and endogenous)

42
Q

B cells differentiate into ___ cells, which produce antibodies to deal with ___ antigens

A

plasma cells; extracellular antigens

43
Q

Are T cells designed to deal with extracellular or intracellular cellular-associated antigens?

A

Intracellular antigens (cell-associated antigens)

44
Q

What are the two possible outcomes due to T cell activation by antigen?

A

1) Production of cytokines, which signal other cells of immune system to become activated (helper T cells)
2) Killing cell possessing or expressing foreign antigen (cytoxic T cells)

45
Q

T cells become activated with the immunological synapse is formed between an ___ and a ___ cell

A

APC (dendritic cell) and a T cell

46
Q

___: a disulfide linked heterodimer glycoprotein belonging to the Ig superfamily of molecules

A

TCR (T-Cell Receptor)

47
Q

True or False: Each member of the Ig Supergene Family is involved in binding or recognition of foreign antigens (HLA, Ig, TCR, etc.)

A

True

48
Q

Like Ig receptors in B cells, the TCR is clonally distributed, which means that?

A

Each T cell clone bears a unique TCR that determines its antigen specificity

49
Q

The majority of T cells have a ___ heterodimer composed of _ and _ chains and mature in the ___

A

TCR heterodimer; alpha/beta; thymus

50
Q

True or False: A smaller population of T cells posses gamma and delta chains (gamma/delta TCR+) and mature without a requirement for the thymus

A

True

51
Q

TCR’s have variable region domains in the alpha and beta chains
(_ and _)

A

Va and Vβ

52
Q

In the Va and Vβ regions of the TCR, the two polypeptide chains come together to form a ____ site (similar to antibody hypervariable region) - this is where antigen binds

A

terminal antigen binding

53
Q

True or False: CD3 is composed of gamma, epsilon and delta chains

A

True

54
Q

True or False: CD3+ is a complex found on all mature T lymphocytes

A

True

55
Q

___ is a chaperone for TCR and is a critical signaling molecule

A

CD3+

56
Q

Which is a member of the Ig superfamily gene: TCR or CD3?

A

TCR

57
Q

True or False: TCR has conserved and variable domains AND recognizes antigens and HLA on APC

A

True

58
Q

Which molecules contain signaling molecules known as zeta chains (CD247) ?

A

TCR

59
Q

Most exogenous exogenous antigens are processed by dendritic cells and presented to:
A. CD4+ T Helper Cells
B. CD8+ T Cytotoxic Cells

A

A. CD4+ T Helper Cells

60
Q

True or False: TCR is noncovalent but closely associated with a number of transmembrane polypeptides (signaling and accessory molecules)

A

True

61
Q

True or False: CD8+ is T cell specific

A

False: CD3 is T cell specific

62
Q

What are the two primary functions of CD3?

A

1) Chaperone for TCR - transports newly made TCR molecules to cell surface
2) Cellular signaling molecule via transmembrane cytoplasmic domains

63
Q

____ molecules are tightly associated with zeta chains, which are two identical polypeptides that are not T cell specific and are mostly intracellular

A

CD3

64
Q

When antigen is process and presented with HLA molecules, it can be recognized and subsequently bound by the antigen binding site of TCR - known as ____

A

Signal 1
- This relays a conformational change that, in turn, activates CD3 and zeta molecule associated tyrosine kinases, and sets of a “cascade of intracellular events” leading to activation of T cell

65
Q

Binding HLA and associated processed peptide to the TCR is stabilized by ____

A

CD4 and CD8

66
Q

CD4 facilitates binding of HLA Class ___ molecules to TCR

A

HLA Class II

67
Q

___ facilitates binding of HLA Class I molecules to TCR

A

CD8

68
Q

___ and ___ are mutually exclusive in mature T lymphocyte

A

CD4 and CD8

69
Q

CD4 and CD8 are ___molecules and also function in _____

A

adhesion; signal transduction

70
Q

True or False: Binding of accessory molecules can function to either positively or negatively impact T cell activation

A

TRue

71
Q

Positive, co-stimulatory interactions (signal 2) include:
1)
2)

A
  1. Binding of accessory molecule B7 (CD80) on APC to CD28 on T cell
  2. CD40 on APC to CD40L on T cell (CD154)
72
Q

True or False: Positive, co-stimulatory interactions (signal 2) are critical to initial activation of a naiive T cell, but are not required for activation of memory T cells

A

True

73
Q

Negative co-stimulatory interactions include:
1.
2.

A
  1. Binding of accessory molecules PD-L1 on APC to PD-1 on T cell
  2. Binding of B7 (CD80) on APC to CTLA-4 on T cell
74
Q

____ binding strongly inhibits T cells and induces Treg differentiation. Further, it is essential for maintaining peripheral tolerance and limiting immune response.

A

PDL1/PD-1

75
Q

Activation of a T Helper cell includes the transcription of ____ and ___ receptor genes

A

IL-2 and IL-2 receptor

76
Q

___: an autocrine growth factor for T cells that induces both proliferation (entering the cell cycle) and eventually a differentiation to effector cell function (production of cytokines)

A

IL-2

77
Q

IL-2 receptor is also known as ___

A

CD25

78
Q

True or False: Memory T cells have fewer activation requirements upon second encounter with antigen and, therefore, are more easily activated than naiive T cells

A

True

79
Q

Once activate in subsequent encounters with antigen, memory cells become either ___ or ___ cells

A

effector or memory cells

80
Q

What interaction is critical for T cell activation?

A

Accessory B7 molecule (on the APC) interacts with CD28 on the T cell

81
Q

When does peripheral tolerance of T cell occur?

A

In the lymph nodes, when T cells are stimulated (MHC/peptide-TCR) without secondary stimulation (B7-CD28)

82
Q

When the primary signal (MHC/peptide-TCR binding) happens without the “second signal” (ex: B7-CD28) it can result in functional inactivation of T cell, known as: ______

A

clonal anergy

83
Q

True or False: Once T cells become anergic, they can only be activated if they encounter their specific foreign peptide/MHC molecule

A

False - Once T cells become anergic, they CANNOT be activated, even encounter their specific foreign peptide/MHC molecule

84
Q

Repeated stimulation of activation T cells can cause the T cell to due by _____

A

apoptosis (clonal deletion)

85
Q

____ cells can inhibit activation of T cells by self-peptide/MHC

A

Regulatory T cells

86
Q

Secondary signal is needed to stabilize ___ mRNA

A

IL-2 mRNA

87
Q

Activation-induced cell death induces expression of ___ and ___, resulting in apoptosis

A

Fas and Fas ligand

88
Q

In activation-induced cell death, expression of pro-apoptotic proteins results in ___

A

apoptosis

89
Q

What are three examples of Regulatory T cells?

A

CD4+
CD25+
Fox P3+

90
Q

True or False: Regulatory T cells suppress/inhibit activation of other T cells, most likely due to production of inhibitory cytokines

A

True

Molecular Immunology (27 decks)

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