Immunity Mediated By B Cells And Antibodies

Front 1

Is Ig by itself destructive?

Back 1

no

Front 2

Do all isotypes of Ig initiate the same signal transduction cascade?

Back 2

yes

Front 3

What is the step of antigen activating BCR?

Back 3

1)antigen binds to BCR
2) tyrosine kinases blk, lyn and fyn become activated
3) blk, fyn, lyn phosphorylate ITAM on Ig&B; and Igα
4)Syk docks on Igβ
5) signal transduction

Front 4

What are the three components of the BCR co-receptor?

Back 4

CD-81
CR 2 /CD 21
CD19

Front 5

What are the complement receptors on B cells? Which one of the complement receptors is in the Co-BCR?

Back 5

CR = complement receptor
CR1
CR2 in co-BCR

Front 6

How is the mechanism of how complement works in B cell activation?

Back 6

1) CR1 binds factor C3b --> iC3b+C3d
2) CR2 binds C3d

Front 7

How does the BCR and co-BCR work together?

Back 7

1)CR2:C3d interaction juxtaposes BCR and Co-BCR
2)BCR lyn tyrosine kinase can posphorylate CD19
3)CD 19 amplifies signal of BCR 100X

Front 8

What are the two types of signals B cells can recieve for activation?

Back 8

1) thymus dependent (TI-1, TI-2)
2) thymus independent

Front 9

How do TI-1 antigens activate B cells?

Back 9

via the innate immune sytem

Front 10

What are examples of the way TI-1 works?

Back 10

1) LPS - specific and non specific
2) Bacterial DNA - specific

Front 11

What is the mechanism for TI-1 LPS B cell activation?

Back 11

1) Specific - anti-LPS mIgM binds LPS, LPS activates TLR4
2) Non specific - anti-another surface molecule IgM and LPS activates TLR<b>4</b>

Front 12

What is the mechanism for Bacterial DNA activation of B cells via TLR4

Back 12

mIg binds DNA
DNA activates TLR<b>9</b>

Front 13

What is the mechanism for how TI-2 antigens work?

Back 13

1) antigens have uniform highly repetitive epitopes
2) they crosslink strongly with BCR and co-BCR
3)generate strong signal

Front 14

Which B cell activation type is produced in congientially athymic individual?

Back 14

TI-1, TI-2

Front 15

What B cell antigen is found to prime T cells?

Back 15

TD only

Front 16

Which B cell antigen activates polyclonal B cells?

Back 16

TI-1

Front 17

Which B cell antigen requires repeating epitopes?

Back 17

TI-2 antigen

Front 18

How does T-dependent response work?

Back 18

1) B cell uses CAMS and integrins to get to T dependent area
2) B cell picks up antigen
-----meanwhile
3)T cell meets up with dendritic cell and gets antigen
4) T cell waits for a B cell with antigen in MHC II
5)cognate interaction occurs
6)T cell has CD40L and B cellhas CD40 receptor
7) T cell sends cytokines to B cell to activate it

Front 19

What is cognate interaction?

Back 19

T and B cell recognize same antigen but different epitopes

Front 20

What cytokines are released from T cell to B cell that stimulate differentiation and proliferation?

Back 20

proliferation- IL4
differentiation - IL5, IL6

Front 21

What do the B and T cell need to do inorder for the T cell to secrete the cytokines to the B cell?

Back 21

T cell needs to reorient its cytoskeleton and secretory apparatus towards the B cell

Front 22

What structure forms after the B:T cell conjugation occurs?

Back 22

Primary focus forms in the T cell

Front 23

When a B cell is in the primary focus what two things can occur?

Back 23

1) B cell matures to plasma cell and goes to bone marrow
2) B cell enters follicle along with T cell to form a secondary focus

Front 24

How is a secondary focus formed?

Back 24

1)A secondary focus is formed when FDCs bind intact antigen
2)FDCs bind antigen using the CR1 and CR2 to bind to 3cd from degradation of complement
3)retain them for long periods of time
4)T cells also help drive the secondary focus formation

Front 25

What is located in the germinal center?

Back 25

1)rapidly dividing B cells in dark zone called centroblasts undergoing somatic hypermutation
2)centroblasts differentiate into centrocytes and move to the light zone

Front 26

How does a helper T cell influence centrocyte fate?

Back 26

Centrocyte without high affinity BCR: T cell interaction will die by apoptosis
Germinal center centrocyte with high affinity surface Ig is cross-linked and antigen is presented to helper T cell

Front 27

What directs isotype switching in B cell?

Back 27

CD40-CDL interaction
cytokines like IL-4, IL-5, INF&gamma;, TGF-&beta;

Front 28

What is hyper IgM syndrome?

Back 28

no germinal centers

Front 29

What causes the lack of germinal centers?

Back 29

T-cells
CD-40L

Front 30

What cytokine directs whether a cell will become a memory cell or a plasma cell?

Back 30

memory cell - (IL 4)
plasma cell - (IL-10)

Front 31

What are the characteristics unique to plasma cells?

Back 31

dfasd

Front 32

What characteristics does a resting B cell have that a plasma cell does not? (5)

Back 32

-Surface Ig
-Surface MHC class II
-Growth
-Somatic hypermutation
-Isotype switching

Front 33

What characteristics does a plasma cell have that a resting B cell does not?

Back 33

high rate Ig secretion

Front 34

Which Ig can cross the placenta?

Back 34

IgG

Front 35

When does a infant start making their own Ig?

Back 35

6 months

Front 36

Where are the different types of Igs located in the body? (3)

Back 36

IgM and IgG: plasma
IgE:epithelial surface
IgA: mucosal secretion

Front 37

What determines the anatomical location and functions of isotypes?

Back 37

Fc portions

Front 38

How does IgG get into the extracellular space?

Back 38

Bramble Receptor=FcRn

Front 39

What is the mechanism of IgG exocytosis? (4)

Back 39

1)FcRN on endothelial wall
2) IgG binds to it and gets into a endocytotic vesicle
3) acidic pH of vesicle causes association with IgG with FcRn protecting it
4)basolateral surface basic pH causes IgG to dissociate from FcRn

Front 40

What two Igs are transported across epithelial cells?

Back 40

IgA, IgM

Front 41

What is the mechanism of IgA/IgM transcytosis?

Back 41

1)poly Ig receptor on basolateral surface of epithelial cell
2) receptor mediated endocytosis
3) transport to apical phase
4) cleavage of receptor

Front 42

What is transcytosis?

Back 42

unidirectional xport of macromolecules through a cell

Front 43

Is neutralization isotype specific?

Back 43

no

Front 44

How do neutralizing antibodies work?

Back 44

block ability of toxin to bind receptor on cell surface and get endocytozied

Front 45

What are the two types of Ig that are best able to activate complement?

Back 45

IgG and IgM (especially IgG3)

Front 46

How does IgM activate complement?

Back 46

1)pentameric IgM
2) binds C1
3) classical C3 convertase to C3a and C3b

Front 47

What is special about IgM activating complement?

Back 47

since it is a pentamer only 1 IgM molecule is needed

Front 48

What does C1 bind?

Back 48

pentameric proteins like IgM pentamer and CRP of innate immune response

Front 49

What is the problem with the IgM and complement response?

Back 49

IgM activates complement efficiently but has limited access to tissues and low affinity

Front 50

What happens once you have a antibody:antigen complex?

Back 50

1) C1 binds
2) classical pathway occurs because C1 activates C4bC2a
3)C3b is made which activates more complement deposition

Front 51

How does IgG activate complement?

Back 51

2 molecules of IgG are needed they bind C1q of C1

Front 52

Does IgG have higher or lower affinity than IgA

Back 52

higher affinity

Front 53

How do erythrocyte help with clearing immune complexes?

Back 53

CR1 on ethryocyte binds C3b
RBC carries complex to liver or spleen where a macrophage gets rid of it

Front 54

What are the advantages and disadvantages of the IgG flexibility?

Back 54

adv: bind two epitopes
disad: hinge is non globular and susceptible to protease degradation

Front 55

Which IgG is the best activator of complement?

Back 55

IgG3

Front 56

What is the least abundant isotype of IgG?

Back 56

IgG4

Front 57

What happens to IgG4 in serum?

Back 57

heavy and light chain exchange so IgG becomes monomeric and therefore non-inflammatory

Front 58

What two effects does IL4 have on isotype switching?

Back 58

promote switching to IgE and IgG4

Front 59

What is the high affinity receptor for IgG?

Back 59

Fc&gamma;RI
&alpha; chain binds with high affinity IgG1 and IgG3
&gamma; chain activates signaling cascade

Front 60

Where is the FC&gamma;RI receptor found?

Back 60

monocytes
macrophages
dendritic cells

Front 61

What is the purpose of the FCR receptors?

Back 61

interact with coated IgG to increase efficiency of phagocytosis

Front 62

Are all FCRs activating?

Back 62

No some FcRs are inhibitory and have ITIMs on cytoplasmic domains instead of ITAMs

Front 63

How do NK cells use Igs to kill infected cells?

Back 63

1)IgG1 binds target cell
2) FcRIII(CD 16) on NK cell binds IgG1
3) NK gets activated to kill

Front 64

How is IgE releated to the allergic response?

Back 64

IgE crosslinking on Fc&epsilon;R results in release of granule

Front 65

Which FcR activates almost all cells? inhibits almost all cells?

Back 65

Fc&gamma;RIIIA (excitatory)
Fc&gamma;RIIIB2 (inhibitory)

Front 66

What is the common activating signal in the FcR?

Back 66

&gamma; chain

Front 67

What Ig do most FcRs interact strongest with?

Back 67

IgG1

Front 68

What are the exceptions to the fact that most FcRs react strongest with IgG1?

Back 68

Fc&epsilon; (IgE)
Fc&alpha; (IgA)

Front 69

Do FcRs have restricted expression?

Back 69

yes, most types of FcR are on macrophages and neutrophiles