isotype diversity

Question 1

The B cell can do three things

Answer 1

secrete antibodies; undergo somatic mutation to create additional diversity; can do isotype switching (eg to can switch between IgA, IgB etc)

Question 2

when a b cell differentiates to a plasma cell, what happens to the Ig expression?

Answer 2

antigen binding site on transmembrane IgM is the same as the one that is secreted

Question 3

how do you get increased variability in expressed IgM etc after immunization

Answer 3

the regions that encode for these immunoglobulins are changed by activation-induced cytidine deaminase. changes one base to a random one in the CDR region

Question 4

what does a base pair change in CDR region do?

Answer 4

it can change the antigen specificity of the antibody molecule. (it can be a neutral, detrimental, or helpful change)

Question 5

what does a base pair change in CDR region called

Answer 5

somatic hypermutation

Question 6

isotype switching results in???

Answer 6

the immunoglobulins will have a different C region, but it will have an IDENTICAL antigen specificity

Question 7

besides somatic hypermutation what does activation-induced cytosine deaminase do?

Answer 7

it helps in isotype switching by splicing out DNA parts for recombination.

Question 8

how does the cell decide to do isotype switching?

Answer 8

gets a signal from cellular cytokines

Question 9

what are the three functions of Ab?

Answer 9

neutralization - Ab binds to antigen or bacteria. hold hostage; opsonization - Ab binds to antigen and then calls for a neutrophil/macrophage to eat it; compliment activation - leads to induce inflammation or proteolysis

Question 10

IgM

Answer 10

first Ig to be synthesized; on naive B cells as monomer; no hinge region; activated B cell will secrete it as a pentamer; 10 potential binding sites; fairly low binding affinity to epitopes; activates the compliment pathway; can agglutinate/crosslink bacteria (ABO blood); can be transported into mucus, intestine, gut

Question 11

IgG

Answer 11

prototypical Ig; high amount in the serum; 4 subtypes; compliment cascade 3>1>2>4; binds to neutrophils and macrophages (opsonization with their Fcgamma receptors)

Question 12

IgG ultrastructure

Answer 12

has a hinge region regardless of the subtype, but makes it more susceptible to proteolytic enzymes

Question 13

IgG 4 is special because

Answer 13

it can dissociate at the disulfide bridges and can then recombine after synthesis to make a hybrid; that makes it less effective sometimes; this type does not activate compliments; its thought to be an anti-inflammatory action to dampen allergic response

Question 14

IgA

Answer 14

this is the other class of molecules that can be present in a multimeric form; both 1 and 2 can be present as dimer; it has a J chain like IgM; it can be transported into respiratory,gut, mucus; neutralization effect; some upper respiratory infection bugs synthesize IgA proteases so that they are not caught and coughed up; therefore, this has a hinge region

Question 15

IgA a compliment?

Answer 15

no. you wouldn’t want any type of inflammation to happen at the mucosal membranes anyways.

Question 16

IgE

Answer 16

usually present in low concentrations; important in protection against helminths, parasites, allergies; lacks a hinge region; has an extra heavy chain constant domain; it binds to the FC sigma receptor on mast cells and basophils which causes them to release inflammatory things

Question 17

IgD

Answer 17

usually present in low concentrations; produced with IgM on naive mature Bcells; you’ll find IgD plasma cells in upper respiratory tract, but we don’t know what they do there

Question 18

what is the biggest Ig

Answer 18

IgM; five times bigger, because its a pentamer

Question 19

what is the Ig that is the msot prevalent

Answer 19

IgG

Question 20

The only two ig that can go across epithelium

Answer 20

IgA, igM

Question 21

only ig that can go across the placenta

Answer 21

igg

Question 22

what changes in ig are reversible?

Answer 22

co expressing IgM and IgD; this is because these changes are done at the RNA level