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immunotech > B cells and their antibodies > Flashcards

B cells and their antibodies Flashcards

1
Q

what are B cells

A

-are cells that are produced from fluid called T cells
- and they produce antibodies

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2
Q

what is Ig

A

they are glycoproteins that binds specifically to the antigen and are important of humoral immunity
they are produced by B cells in response to pathogen

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3
Q

when is Ig called antibody

A

when they secreted by B cells

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4
Q

when is Ig called B cell receptor (BCR)

A

when they bound on membrane of B cell

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5
Q

What is the purpose of BCR

A

is to guide B cells in there development

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6
Q

what is the purpose of antibody

A

to protect our body against pathogens/ diseases

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7
Q

how does structure of antibody

A
  • 2 alpha and beta chains
    -it have 2 antigen binding sites
  • it have constant and variable region with 2 identical heavy chain and 2 identical light chain
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8
Q

what are the regions of antibody

A
  • variable region : variable aa sequence. VH and VL, forms antigen binding sites
  • Constant region : constant aa sequences. determine effector function
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9
Q

what are 3 fragment of antibody

A
  • Fv region : fragment variable
  • Fab region: fragment antigen binding
    -FC region: fragment crystallizable
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10
Q

important to know that Fc and C region

A

C region is not Fc region

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11
Q

structure of antibody vs BCR

A
  • BCR has Ig beta and Ig alpha chain used in signaling
  • antibody don’t have them
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12
Q

how does structure of antibody relate to it’s function

A
  • variable region: contain antigen binding site and recognize the target antigen.

-constant region: translate the binding of target antigen to the effector function, in few words it ensures proper effective function to antigen take place

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13
Q

how do we get antigen binding sites

A
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14
Q

how is the shape of antibody binding site

A

binding site shape depends on the antigen
when is small protein so called hapten it has deep pocket shape but when protein is large it has flat surfaces

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15
Q

how does antibody binds antigen

A

through non-covalent bonds ( H-bonds, hydrophobic, and Vdw forces)

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16
Q

antigen specificity

A

-Ab binds specific part of Ag called epitope
-two antibodies can binds one antigen but different two epitopes of antigen
- antigen have different epitopes

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17
Q

two types of epitopes

A

conformational (discontinuous) and linear (continuous)

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18
Q

what are five class of antibody isotypes

A

are IgG, IgM, IgD, IgE and IgA, all classes have same variable region but each class have specific constant region with specific effector function

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19
Q

what do B cells produce

A

-each B cells produce antibodies with one specific aa sequence structure

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20
Q

what kind of antibodies are produced by B cells

A
  • antibodies that recognize appropriate antigen and
  • antibodies that generate appropriate effector function
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21
Q

when does antibodies obtain their specific structure

A

during B cells development

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22
Q

how do B cell develop

A
23
Q

what are 7 characteristic of B cells / must and their solutions

A
  • must be able to produce antibodies against antigen they never encounter before
  • by creating many different cell that produce antibodies and they will divide and survive

-must avoid producing antibodies that fight against our own body
* eliminating cells that produce unsuitable antibodies
* eliminate T cells that help B cells to produce antibody with unsuitable binding sites

-must know when to initiate response against antigen
*communicate with T cells

-must be able to increase affinity of antibodies to specific target antigen
* somatic hypermutation and selection

-must give antibodies appropriate characteristics to perform specific effector function
* change of immunoglobulin constant region/ class switch which is induced by enzyme A

-must produce large amount of antibodies to fight against antigen
* development of short lived and long lived plasma cells

-must provide body with immunological memory that ensure production of more and better antibodies
*produce long lived memory cells encoding appropriate antibodies

24
Q

how does B cells be able to produce antibodies for antigen they never encounter before

A

by creating many different cell that produce antibodies and they will divide and survive

25
Q

what is negative selection related with must 2

A

when there is elimination of clones/B cells that produce antibodies with inappropriate binding properties

26
Q
A
27
Q

where is antibody variability more concentrated

A

in V domain in VH- hyper variable / heavy variable region or in CDR

28
Q

where do we find 6 CDR that form antigen binding site

A

3 are found in VH and other 3 on VL

29
Q

how is antibody encoded

A

through 4 process or principles:
- somatic recombination: rearrangement of V,D and J gene to form complete V region of antibodies
-junctional diversity: is shown during recombination of VJ and VDJ
-combination of differentVH and VL domain : if 3 VH and 3 VL are combined we can get 9 antibodies
all above 3 take place in bone marrow
- Somatic hypermutation this take place in germinal center

30
Q

what is irreversible process

A

when V region of antibody is formed by V and J genes

31
Q

where does somatic recombination occurs

A

in bone marrow where B cells precusor are developed

32
Q

what is non-precised process

A

recombination of VJ and VDJ segments

33
Q

how is B cells activated and its first and second signal

A
  • it is required to be stimulated by antigen through BCR which is signal one
    -present antigen on MHC class II
  • talk to CD4+ T helper cells that recognize the same antigen which is signal two
34
Q

what are two signal of B cells

A
  1. antigen binds to BCR
  2. CD4+ T cells recognize MHC class II- peptide complex on BCR surface
35
Q

How does the TH-cell know when to communicate with the B cell?

A

by T cells being activated by dendritic cells (by when TCR bind to MHC class II of dendritic cells) and and T cells will later activate B cells

36
Q

explain 3 signal of T cells

A

1.TCR/CD4 that binds to MHC II peptide complex of dendritic cells
2. CD28 that binds to CD286/80 of dendritic cells
3. CD40L that binds to CD40 of dendritic cells

37
Q

how does second signal of B cells occurs

A

when T cells is activated by dendritic cells they produce CD40L that bind to the BCR of B cells and activate it

38
Q

what is linked recognition

A

is when T cells activate B cells and they can both recognize different epitope of antigen as long as they belong to same antigen

39
Q

what does B cells do after being activated

A
  • they differentiate into memory or plasma cells
40
Q

where does antibody proliferate or divide

A

into primary follicles and they form germinal centra

41
Q

where in germinal centra do we find cetroblast and centrocytes

A

cetroblast in dark zone and centrocytes in light zone
cetroblast they proliferate at higher degree than centrocytes

42
Q

what is somatic hypermutation

A

process where random mutation is produced while B cells proliferate and can lead to single aa substitutions

43
Q

what is follicular dendritic cells

A

capture antigen on their surface in order to make it accessible to B cells.
only B cells with high affinity of CDR will be able to bind

44
Q

what is positive selection

A

B cells with low affinity BCR will not be able to bind antigen so they can not bind MHC II of T cells.

and they will be killed by apoptosis

45
Q

how does antibodies goes from one class to another

A
  • naive B cells : produce IgM and IgD.
    so in order for B cells to produce other isotype they have to go through class switch, by replacing constant region (between mouse and human) while retaining variable region
46
Q

what does it mean class switching process to be irreversible

A

means once one constant region gene is moved out it can not be included again

47
Q

where does class switch occure

A

in germinal centra in dark zone (centrobrust) only for B cells that has been activated by T cells

and once they get activated they receive signal on which class they should switch to

48
Q

different IgG and IgM

A

IgG has high affinity and fewer binding site
IgM has low affinity and more binding site

49
Q

what is avidity

A

total binding strength of antibody
that why IgM is considered as best antibody to fight antigen due to its more binding site

50
Q

what is plasma cells

A

-short-lived plasma cells are B cells that do not enter into the germinal centra to differentiate.

-long lived plasma cells are B cells that enter in germinal centra to differentiate

51
Q

what antibody does short-lived plasma cells produce

A

IgM that can act on antigen immediately

52
Q

what antibody does long-lived plasma cells produce

A

IgG in large quantity and they reside in bone marrow

53
Q

what is B cell memory

A

B cells that are develop in germinal centra can also be differentiated into memory B cells

54
Q

do study question on slide 81

A

immunotech (16 decks)

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