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CRG RUSVM Immunology > lymphocytes and their receptors > Flashcards

lymphocytes and their receptors Flashcards

1
Q

what are lymphocytes important for

A

lymphocytes are important for the adaptive immune response

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2
Q

what are the 3 major types of lymphocytes

A
  • T lymphocytes (T cells)
  • B lymphocytes (b cells)
  • NK cells
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3
Q

what is the function of T lymphocytes (t cells)

A

t cells regulate adaptive immunity are responsible for cell-mediated immune responses

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4
Q

what is the function of the B cells

A

B cells are responsible for antibody production

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5
Q

what is the purpose of the NK cells

A

NK cells that play a role in innate immunity (LGL, large granular lymphocytes)

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6
Q

what is the morphology of lymphocytes

A
  • lymphocytes are small round cells, T to 15 microns in diameter
  • Have a large round nucleus
  • the nucleus is surrounded by a thin rim of cytoplasm
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7
Q

when does T cell development begin

A

T-cell development begins well before birth

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8
Q

Pre-T cells leave the bone marrow and migrate to the ______ and are called _______

A

Pre-T cells leave the bone marrow and migrate to the Thymus and are called Thymocytes

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9
Q

what are the two types of t cells that form when the t cell receptors begin to form

A
  1. alphabeta T-cell
    1. t cells that express the beta chain
  2. Gammadelta T cell
    1. cells that express gamma or delta chain
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10
Q

Complementarity between the antigen and the TCR dictates the

A

specificity of a response

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11
Q

what is an epitope

A

one TCR for one antigen

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12
Q

how many genes do humans have

A

20,000

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13
Q

what allows the TCR to recognize different antigens eventhough they are epitope

A

Random rearrangement of germline gene segments encoding TCR components

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14
Q

is the random rearrangement of the germline gene unique to T cells

A

No this feature is also shared with B cells

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15
Q

where does the germline gene segment rearrangement take place

A

takes place in the thymus

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16
Q

are the genes that encode for the alpha and beta chains for TCR contiguous?

A

no they are not contiguous

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17
Q

what are the segments in the different regions of DNA labeled as (there are 4)

A
  1. Variable
  2. Joining
  3. Diversity
  4. Constant
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18
Q

Is the alpha or beta chain the first to undergo rearrangement of TCR gene rearrangement

A

Beta chain

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19
Q

what are the steps for the Beta chain rearrangement

A
  1. Random joining of a Dbeta and Jbeta gene segment
  2. Random linking of the new DJbeta segment with a Vbeta segment
  3. Formation of the variable region of the beta chain
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20
Q

what are the steps for the alpha chain TCR gene rearrangement

A
  • Valpha and Jalpha gene segments are joined to make a complete alpha-chain variable region
  • Then VJalpha segment is joined with a Calpha region segment
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21
Q

what are the two genes that make rearrangement of the segments possible

A
  1. recombination activating gene 1 and 2
    1. RAG1
    2. RAG2
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22
Q

Enzymes such as _________, excise the intervening DNA to increase diversity of the TCR

A

Enzymes such as DNA dependent protein kinase, excise the intervening DNA to increase diversity of the TCR

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23
Q

what are the two steps called for sorting and selecting T cells that takes place in the thymus

A
  • positive selection
  • negative selection
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24
Q

what is positive selection

A

a test of whether a newly created TCR can bind to the MHC 1 or MHC 2 on thymic cortical epithelial cells (APCs)

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25
how does a T cell pass the positive selection
the T-cell should bind the MHC in order to pass the positive selection
26
how does a T cell fail the positive selection
if a T cell does not bind the MHC, it fails the positive selection and is eliminated by apoptosis
27
Why is the positive selection of the T cells used
* eliminates thymocytes that: * have failed to assemble a TCR * or have assembled a useless TCR * Also the commitment of T cells to either a CD4+ or a CD8+ lineage
28
what percentage of cells can fail positive selection and undergo apoptosis
as much as 96%
29
What is negative selection of T cells
if a T cells TCR binds with high affinity to an MHC-antigen complex present on an APC, the T cell dies through apoptosis
30
What does negative selection eliminate
negative selection eliminates most thymocytes that react with self as represented in the thymus
31
do early thymocytes have CD4 and CD8 receptors and what are these cells called
* no early stage thymocytes lack CD4 and CD8 * they are known as double-negative cells
32
when are CD4 and CD8 expressed and are subsequently known as
CD4 and CD8 are expressed once the alphabeta TCR is expressed: these cells then become double positive T cells
33
what is the difference between immature and mature T cells in their expression of CD4 and CD8
* Immature cells express both CD4 and CD8 (double positive T cells) * Mature T cells express only CD4 or CD8 (single positive)
34
How is a T cell chosen to express CD8
if the TCR has an affinity for an MHC 1 , the thymocyte turns off the CD4 gene and begins to express CD8 solely
35
How is a T cell chosen to express CD4
If the newly formed TCR has affinity for MHC class 2 molecules that lymphocyte switches of the CD8 gene and expresses only CD4
36
how do cells that have passed both positive and negative selection leave the thymus
via the blood
37
what do CD8+ T cells become
cytotoxic T cells
38
what do CD4+ T cells become
* helper T cells * eventually differentiating into Th1, Th2, Th17 etc after antigen encounter * Some CD4+ T cells differentiate into regulatory T cells
39
Why is the AIRE (autoimmune regulator gene) important
allows thymic epithelial cells to express many of the proteins usually found in other tissues of the body
40
what are the major groups of receptors on T cells
1. TCR: antigen receptor 2. Cytokine receptors 3. antibody receptors 4. complement receptors 5. adhesion molecules 6. Regulatory receptors 7. Transport receptors 8. chemokine receptors
41
what are the three stages of B lymphocyte development
1. Maturation 1. generation of mature immunocompetent B lymphocytes 2. Activation 1. contact of B lymphocytes with specific antigens 3. Differentiation 1. activation of B cells become plasma cells that produce antibodies or become memory B cells
42
where do By lymphocyte develop in most vertebrates
in the bone marrow
43
during prepaturition where do b lymphocytes developed
yolk sac, fetal liver, bone marrow
44
where does b lymphocyte development take place post parturition
bone marrow
45
what are progenitor cells (Pro-B)
cells that differentiate from lymphoid precursor cells into B lymphocytes
46
when do Pro-B cells differentiate into B lymphocyte precursor cells
when the cells are in the presence of IL-7 and bone marrow stromal cells
47
what first appears on the pro-B cells
1. heavy chains (H) 1. followed a V S J rearrangement and further alpha and beta chains of poly-Ig 2. Light chains are rearranged at the pre-b cell stage
48
what types of light chains are expressed on pro-b cells
because of the allelic exclusion only one type of light chain can be expressed (V J) K or gamma
49
after the pre B stage where H chain undergoes V, D, J rearrangement and the light chain has V and j Rearrangement what cell stage is the b cell in
immature b cell
50
what do the membrane-bound IgM and Igalpha/beta chains form
these proteins form the b lymphocyte cell receptor complex (BCR)
51
what two recombinases regulate the chain rearrangement in B cells
RAG1 and RAG2
52
what happens if the BCR on an immature B cell is stimulated
this would lead to cell death or anergy (lack of response)
53
when is full maturity of B cells attained
when membrane bound IgD is expressed
54
what must happen in order for IgD to be expressed on the membrane of the B cell
This requires a change in RNA coding to allow coding of both heavy chains ( mu and delta (IgM and IgD))
55
what percentage of b cells produced in the bone marrow daily reach circulation
10%
56
what happens to the b cells that do not make it to circulation
eliminated through negative selection or clonal deletion
57
Why would negative selection of clonal deletion eliminate B cell
these methods eliminate B cells that have high affinity for self-antigens
58
what happens to the B cells that enter circulation and arrive at the periphery
they undergo activation and differentiation into plasma cells
59
how many polypeptide chains do the B cell receptors have
4 polypeptide chains
60
the 4 polypeptide chains of B cell receptors make up
2 identical heavy chains and 2 identical light chains
61
how are the light chains bound to the heavy chains in the B cell receptor
disulfide bonds
62
how are the H chains bound to each other in the b cell receptor
they are bound similarily to the Light chains with disulfide bonds
63
what is important about the C-terminal of the H chain that spans the cell membrane
they are identical for each Ig isotype
64
what is important about the N terminal (membrane-distal) portions of the H chains
they are highly variable
65
what is the similarity of the N-terminal portions of the H and Light chains
both N terminal portions of L and H are highly variable
66
what are Igalpha/IgBeta
signalling molecules
67

CRG RUSVM Immunology (8 decks)

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