Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Immunology > Assignment 6 > Flashcards

Assignment 6 Flashcards

1
Q

what is the role of B lymphocytes?

A

express antigen recognizing receptors (antibodies) on their cell surface - the receptors mediate the interaction between the B cell and the intact antigen

  • Interact with antigen and process/present it to CD4+ T cells
    • Antibody factory following differentiation of plasma cells
    • Some differentiation to memory B cells
    • Express antigen receptors (mIg) on cell surface
  • BCR complex
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

at what developmental phase does progenitor B cell acquire its antigen specific receptor (immunoglobulin)?

A

hematopoeisis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

membrane immunoglobulin (mIg) are expressed in associated with heterodimer, ______

A

CD79a/CD79b = Ig alpha/Ig beta

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is the role of CD79a/CD79b = Ig alpha/Ig beta?

A

couples mIg to intracellular signaling pathways

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

in naive mature B cells, they heavy chain constant regions are ____ and ____, while the light chain constant regions are either _____ or _____

A

mu
delta

kappa
lambda

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what segments make up the light chain variable region of the mIg?

A

V and J

variabel and joining

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what segments make up the heavy chain variable region mIg?

A

V, D and J

variable, diversity and joining

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

the variable regions of the light and heavy chain are encoded in the genome by segments that are _______ during B cell development

A

randomly!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

the constant regions, light and heavy chain differ from ______ but are the ____ in all antibodies

A

one another

same

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

why do light and heavy chains have more potential diversity for the B repertoire?

A

because they are not restricted in their association

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

where is the antigen binding site contain within?

A

combined variable regions of the light and heavy chain = hypervariable regions = complementary regions = paratope

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what types of forces are between the antigen and antigen binding site on the antibody?

A

non-covalent - this means antigens can come on and off!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what does the attraction between the antigen binding site and an epitope determine?

A

affinity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

the overall attraction, including all Fab regions is referred to as ?

A

avidity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

the construction of different mIg on B cell clones is the result of?

A
  • multiple copies of germline V,D and J gene segments
  • random selection and combination of V,D, and J gene segments
  • junctional diversity generated by the addition or deletion of bases
  • random assortment of light and heavy chains
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

the random selection of V,D, and J gene segments generated B cell receptors that may be_____

A

autoreactive => those B cells must be deleted or inactivated!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

define somatic recombination

A

the process in which DNA in the loci that encode the variable region is cut and recombined to make an intact gene for the variable regions of the light and heavy chains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

the variable region gene and constant region genes are transcriibed into hnRNA which is spliced to mRNA which is translated to a light chain and a heavy chain

A

the variable region gene and constant region genes are transcriibed into hnRNA which is spliced to mRNA which is translated to a light chain and a heavy chain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

where does transcription and translation of light and heavy chain genes occur?

A

bone marrow during B cell development

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

how many B cell clones can an individual generate? aka total diversity of BCR

A

10^9 to 10^11 - each having mIg whose variable regions will differ from those present on other clones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what do the B cell clones collectively represent?

A

B cell repertoire

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

how is the diversity among B cell clones possible?

A

because of V,D, and J segments which encode the variable regions and are present as multiple germline genes

23
Q

how is recombination triggered?

A

activation of recombinases, nuelceoprotein products of the RAG-1 and RAG-2 genes (recombination activating genes)

24
Q

gene rearrangement of the variable light chain involves the selection and ligation of what?

A

1 J and 1 V to = VJ segment

25
Q

gene rearrangement of the variable heavy chain involves the selection and ligation of what?

A

1 D and 1 J to = DJ gene segment which combines with a randomly selected V gene segment to = VDJ of a heavy chain!

26
Q

what is the random selection of V (D) and J referred to as?

A

combinatorial diversity

27
Q

what happens to the intervening Vs, Ds or Js during recombination of either light or heavy chains?

A

they are deleted!

28
Q

how is junctional diversity generated?

A

additional DNA nucleotides may be deleted or added at V, D or J gene segment junctions in order to maintain (downstream) an open reading frame

29
Q

what template independent DNA polymerase mediates the incorporation of nucleotides at junctions?

A

terminal deoxynucleotidyl transferase (Tdt)

30
Q

describe allelic exclusion

A

the successful rearrangement of a heavy chain variable region from 1 chromosome (maybe from mom) inhibits the somatic recombination of the heavy chain variable region of the other membrane of the chromosome pair (maybe from dad)

31
Q

what is the net effect of allelic exclusion?

A

all mIg present on the cell surface of any B cell will have the same heavy chain variable region

32
Q

B cell differentiation in the bone marrow occurs before any exposure to what?

A

foreign antigen

33
Q

what is B cell differentiation characterized by

A

expression and silencing of distinct sets of genes at discrete stages of development

34
Q

what is the ultimate goal of B cell maturation?

A

to generate a B cell repertoire that is non-autoreactive!

35
Q

what is the Pro-B cell stage (transcription) characterized by?

A

transcription of multiple genes => RAG-1 and RAG-2, CD19, Tdt and CD79

36
Q

what is the Pre-B cell stage (Expression of Pre-BCR) characterized by?

A

expression of a pre-B cell receptor (pre-BCR) in association with the CD79a/CD79b heterodimer.

37
Q

what makes up the pre-BCR

A

2 mu heavy chains with variable region that has been rearranged by somatic recombination

2 heavy chains are paired with 2 pseudo light chains!

38
Q

what directs proliferation and further differentiation of pre-B cells?

A

signaling via the pre-BCR complex

39
Q

what genes are expressed in the Pre-B cell stage?

A

pre-BCR
CD79a/CD79b
CD19 (continues)
CD20 (introduced!)

40
Q

at what stage does recombination of the light chain variable region occur?

A

Pre-B cell stage

41
Q

at what stage does recombination of the heavy chain variable region occur?

A

Immature B cell stage (Tolerance induction)

42
Q

what characterized the Immature B cell stage?

A

shifts in receptor expression from Pre-BCR to BCR

43
Q

what does the shifts in receptor expression from Pre-BCR to BCR require?

A

assembly of the somatically rearranged light and heavy chains with CD79 to form BCR and translocate to the cell surface - pre-BCR is down regulated

44
Q

how is specific inactivation of B cells expressing autoreactive mIg (tolerance induction) is accomplished by..

A

apoptosis or induction of anergy (non responsiveness)

45
Q

why is tolerance induction only possible in the Immature B cell stage?

A

because novel BCR is expressed on the Cell surface

46
Q

what is the mature B cell stage characterized by?

A

co-expression of cell surface IgM and IgD => consequence of alternative splicing!

mature B cells leave the bone marrow, enter blood stream and migrate to peripheral lymphoid tissues. They recirculate if they do not encounter antigen in secondary lymphoid tissue

47
Q

what level of alternative splicing occur at and what is the result?

A
  • occurs at the hnRNA level

- leads to expression of both IgM and IgD on cell surface

48
Q

what mediates the exit of B cells from blood into peripheral lymph nodes?

A

adhesive molecules (Lselectin) on B cells

49
Q

what does Lselectin on B cells interact with

A

vascular addressin molecules present on high endothelial HEVs

50
Q

what is the role of addressins?

A

control sites of “homing” for B cells

different addressins are expressed in peripheral lymph nodes vs. intestinal mucosal HEVs

51
Q

what are mutation in Btk kinase associated with

A

X-linked agammaglobulinemia

52
Q

what is the role of Btk

A

plays a critical role in B cell activation, differentiation and proliferation

53
Q

where does the initial block in B cell development occur as a consequence of Btk defect?

A

pro-B to pre-B cell transition => pre B cells are defected and maturation is stopped at this point = cannot enter circulation

54
Q

in XLA pts, what numbers of B cells in the peripheral blood is seen and what are serum Ig levels? What does this suggest

A

low
low
- suggests that presence of a compensatory pathway that can at least in part, take over the role of Btk in human B cells…

Immunology (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions