Lecture 11

Question 1

What are antibodies?
Produced by?

Answer 1

Any substance that prompts to trigger an immune response
Also called immunoglobin (Ig)

Produced by plasma cells (b cells) in response to & counteracting specific antigen

Question 2

What is the structure of a B cell receptor & Ig?

Answer 2

Has 2 heavy and 2 light chains
Has Fab ( antigen binding)– both light and heavy
And Fc domain– heavy chain only

FAB + FC joined by disulfide bonds

Question 3

What is an epitope?
What do antibodies recognize?

Answer 3

Specific portion of antigen that is contacted by antibody

Native epitopes

Question 4

What are Ig distinguished by?
What is an isotope?

Answer 4

Their heavy chain constant region
– have different constant FC domain that recognize differnt genes

Dif Ig products——isotopes
IgM, IgD, IgG, IgE, IgA

Question 5

What is the difference between isotype, idiotype, and allotype?

Answer 5

Idiotype is antigent specificity, which is different for every clone (IgG can be against antigen A or antigent B)

Isotype is the class of antibody determined by the structure of the Fc fragment (IgA, IgG)

Question 6

What is the most abundant isotype?
How do IgG and IgM differ in their ability to bind antigen molecules?

Answer 6

IgG, it is bi valent
IgM is a petamer with 10 identical binding sites

Question 7

How many antibody types are there?

Answer 7

IgA
IgD
IgE
IgG
IgM

Question 8

What is the role of IgM and IgG?

Answer 8

IgM: first antibody made during primary response
-against bacteria in early stage of antibody response
-found on surface

IgG: major antibody in late primary response & main antibody of secondary response
-main in blood
-secreted & crosses placenta

Question 9

What is role of IgA and IgE?

Answer 9

IgA: protect mucosal surface
- secreted in breast milk
- forms dimer

IgE: allergy & anaphylaxis
- secreted in allergic reactions

Question 10

What is function of IgD?

Answer 10

Found on surface bound form
-need for B cell maturation

Question 11

What are the 3 main ways by which antibodies function to protect the host?

Answer 11

Neutralization—binds toxin & blocks from entering its targets

Opsonization: —-binds bacterium via Fab region, then macrophages recognize Fc region

Complement activation

Question 12

What is B cell developement indepents of & what is needed for activation?

Answer 12

Antigen
Need antigen

Question 13

What happens during development of B cells?

Answer 13

Differtiate from precursor cells

Undergo random DNA recombination— receptor generated

Make sure there is single clone of BCR per cell (Allelic exclusion)

Eliminate that self regonize (self tolerance)

Question 14

What is BCR gene rearrangement?
Where does it occur?
How does it result in different gene sequences in each B cell?

Answer 14

DNA (VDJ segments) rearrangement of antigent receptor genes

In bone marrow

Permeantly changes receptor gene sequences, resulting in new & uniqe specificity

Question 15

What causes diversity of V regions ??

Answer 15

Random recombination of VDJ

And by random mutations

Question 16

What are require ments of successful VDJ recombination?

Answer 16

Requires RAG1 &RAG2 & DNA modifying enzymes

—successful—> prevents further recombination
—-unsuccessful—-> attempts again

Question 17

How does B cell development begin (what chain is first)?

Answer 17

Heavy is first—-DJ rearrange and rearrange VDJ (must not mess up)
Then moves onto light—-VJ rearrange (can mess up)

Question 18

What is somatic hyper mutation?
What immune cells are affected by?
Selection?

Answer 18

Or affinity maturation occurs in B cells following antigent contain

V regions of antibody undergo rapid point mutations— resulting in many variations in binding affinity

Those that bind the antigen the best & postively selected

-only affect somatic cells and are not inherited

Question 19

What is class switching?
What status the same?
What does this allow?
Where does this happen?

Answer 19

-changing of the constant region of BCR to switch from MEMBRANE bound to SECRETED
-allows Vh Exxon to be associated with different Ch genes
-switches constant region of B cells receptor

V regions is the same, which keeps antigen specificity same

Differentiate into antibody secreting plasma cells& make other antibodies ( diff isotypes)

In germinal centers

Question 20

What does immature B cells express?

Answer 20

IgM and IgD

Question 21

To generate viable BCR, precursors undergo_____ in __ stage

To verify functions ___ chain via ___ recombination, pro ___ cells express ____

To ensure single clone ,, VDJ recombination is blocked by ___

Answer 21

H chain VDJ recombination in pro B stage

H chain via VDJ, B cells, pre BCR

—-pre BCR signaling

Question 22

What two signals are required to activate B cells???
Activated by what types of cells?

Answer 22

By T helper follicular cells (both respond to same antigen)

T-B interaction—-> TCR (T) and MHC (B)
CD40L (T) and CD40(B)

Question 23

What are germinal ceneters?

Answer 23

Micro environment in the center of follicles where GC B cells go proliferation & apoptosis

Question 24

What is plasma cells & memory B cell?
Relationship?

Answer 24

Plasma— factory to produce secreted antibodies

B cell— remembers previous infection and can differentiate into plasma cell

Question 25

Initial contact with cognate antigen results in the _____ and _____ of ___ cells resulting in a _____ that expresses ____ of low affinity During proliferation, _______ selects subclones of ____. Recognition of the _______ cells, _________ resulting in B cell subclones that express and secrete different _______. These subclones develop into _______, that remain in circulation after the antigen has been removed. At the second antigen contact, ______ are activated , resulting in a more rapid, stronger, and more specific immune response

Answer 25

Activation & proliferation of B cells —-> clone, IgM Somatic hyper mutation, higher affinity Antigen by helper T cells, activated class switching, different antibody isotypes Long lived memory cells Memory cells

Question 26

How do primary and secondary B cell responses compare in terms of antigent contact ?

Answer 26

First antigen contact leads to primary response, secondary response happens with subsequent antigen contact

Question 27

How do primary and secondary B cells responses differ in antibody production?

Answer 27

Secondary gives more antibody production

Question 28

How do primary and secondary B cell responses compare in antibody affinity ?

Answer 28

Secondary is strong affinity for antibodies

Question 29

How do primary and secondary B cell responses compare in memory cells?

Answer 29

Memory developers during primary response and are needed for enchances secondary responses

Question 30

How do primary and secondary B cell responses compare in antibody isoytpe & speed of response?

Answer 30

Isotype: primary response & class switching Memory express isotype so that during secondary response, final isotype is expressed right Seconadry is more rapid

Question 31

What is responsible for the ability of BCR to regonize billions of distinct molecules structure ?

Answer 31

process that change variable region allow for receptors to recognize a lot includes: inclusion of diff gene segments (VDJ) to make the variable region & random motions where these segments are joined

Question 32

how are B cells with specificity for the next infectious agent amplified and others not?

Answer 32

B must be activated with antigen specific to their BCR then need conformation signal from T cell before can proliferate