Immunology Chapter 4

An antibody is a _____ BCR

Secreted

Name the 3 components of an amino acid

N group, central Carbon, Carboxy

What are the 5 classes of antibodies

IgG, IgA, IgM, IgD, IgE

What is the antibody repertoire?

Total number of antigen specificities

What can an antigen be?

Anything a BCR or TCR can bind to

Immature B cells have _____ on their surface

IgM

What do mature B cells have on their surface?

IgM and IgD

What protease cleaves the antibody into Fab and Fc fragments?

Papain

What does Fab stand for?

Fragment Antigen Binding

What does an Fc fragment do?

Binds to Fc receptors

What is Agammaglobulinema?

An inability to make an Ab response

What is the yellow component? What is the green?

Yellow: Light chain; Green: Heavy chain

What kind of bonds do peritopes make with epitopes?

Noncovalent

What kind of bond links the light chain with the heavy chain?

Covalent disulfide

The stem of an antibody is referred to as the ______ domain

Constant

What color is the variable region? The constant region?

Red; Blue

What is affinity?

The tightness of binding of an antibody site to an antigen

What is avidity?

The firmness of associated between a multideterminant antigen and the antibodies produced against it

How many isotypes are there of the light chain? What are they called?

2; κ & λ

What defines the immunoglobulin isotypes? (i.e., IgE, IgD, etc.)

Heavy chain constant region

What is the V region at the N terminal of the H or L chains composed of?

V domain, VH or VL

___ and ___ form the antigen binding site

VH and VL

What is the constant region of the light chain composed of?

CL domain

What is the constant region of the heavy chain composed of?

3-4 C domains (CH1-4)

___ and ___ have 4 domains with no hinge regions

IgM and IgE

How many CDR or HV regions in one binding site of an Ig?

6

What is another name for epitope?

Antigenic determinant

What is a multivalent antigen?

An antigen with two or more different epitopes

What is the difference between a discontinuous and linear epitope?

Linear is formed with contiguous amino acids; discontinuous uses different parts of the polypeptide

What is somatic recombination?

Bringing together V, D, and J segments to make a functional gene

What kind of cells can go through somatic recombination?

B cells

What is a monoclonal antibody?

Antibodies with identical antigen binding sites made from a single clone of a B cell

What does a flow cytometer do?

Allows individual cells to be identified by monoclonal Abs (CD markers)

____ codes for light chain CDR1&2

V segment

____ codes for light chain CDR3

V/J junction

____ codes for heavy chain CDR3

D segments; V/D & D/J segments

Can T cells use RAG1&2 to rearrange genes in the bone marrow? (T/F)

False; only B cells

Where does BCR somatic recombination occur?

Bone marrow

What does RSS stand for?

Recombination Signal Sequences

Can a B cell express RAG-1&2 in a secondary lymphoid tissue after activation?

No

What is VDJ recombinase?

Set of enzymes needed to recombine V, D, and J gene segments

What is the function of enzyme TdT?

Adds nucleotides randomly

What is the germline configuration?

DNA that has not been recombined/changed by somatic recombination (original DNA)

Define junctional diversity

Variation present in immunoglobulin and T-cell receptor
polypeptides that is created during the process of gene
rearrangement

What are P nucleotides?

Palindromic nucleotides; Additional nucleotides created after RAG opens hairpin in DNA

What are N nucleotides?

Non-templated nucleotides; Random nucleotides added by TdT

Recombination does not occur at every junction (T/F)

False

What is allelic exclusion?

Ensures only one heavy chain and one light chain is created

Are B cells diploid or haploid?

Diploid

When does somatic hypermutation take place?

After activation

Is μ always expressed on a immature B cell? (T/F)

True

When IgM and IgD are on a mature B cell, do they have the exact same binding site?

Yes

Are Igα and Igβ found on every Ig isotype?

Yes

Igβ is a BCR isotype (T/F)

False

IgG, IgD, and IgE change their isotype in the ___, IgM and IgD change their isotype in the ___

DNA; RNA

Immature B cells express both IgM and IgD on their surface (T/F)

False

What allows for the antibody to be soluble/secreted?

Hydrophilic sequence

What does somatic hypermutation do?

Introduces point mutations (single nucleotide substitutions) throughout V regions at a very high rate

What is activation-induced cytidine deaminase (AID)?

Enzyme that converts cytosine to uracil, which is then excised and replaced with normal DNA bases

What enzyme is somatic hypermutation dependent on?

Activation-induced cytidine deaminase (AID)

What is the benefit of somatic hypermutation?

Enables selection of B cells
making higher-affinity antibodies

____ has the highest avidity out of all of antibody isotypes

IgM

Define affinity maturation

The increase in affinity of the binding sites of antibodies

What is the first antibody produced during an immune response?

IgM

IgM has a (low/high) affinity but a (low/high) avidity

Low affinity; high avidity

IgM is secreted as a _____ with ___ binding sites

Circular pentamer; 10

Define isotype/class switching

The process by which a B cell changes the class of immunoglobulin
it makes

What enzyme is used during isotype/class switching?

AID

What occurs during isotype switching?

A somatic recombination process that attaches a different heavy-chain C-region gene to the existing V-region exon

What is the result of isotype switching?

Production of Igs with different C regions but identical antigen specificities

Switch regions are in front of every C gene except for ___ gene

δ

Why is there no switch region in front of the δ gene?

It is already being made in the RNA

Transcription begins at the ___ switch region

μ

What does AID do in isotype switching?

Changes cytosine to uracil in the Sμ and Sγ regions

What happens after the Sμ and Sγ regions are targeted by AID?

DNA in both regions is nicked on both strands and are looped/cut out

When does isotype switching occur?

After activation

Where does isotype switching occur?

Secondary lymphoid tissue; in germinal center of follicle

Isotype switching is a recombination event (T/F)

True

Does isotype switching take place in the DNA or the RNA?

DNA

Antibodies with different constant regions do not have different effector functions (T/F)

False

How many subclasses of IgG are there?

4

There are ___ subclasses of IgA

2

Do antibodies kill anything directly?

No

What is the main function of IgM?

Activates classical complement pathway

IgM is principally made by ____ cells in ____ organs

Plasma; lymphoid

IgM is composed of __ four-chain units with ___ combining sites

5; 10

What is the most abundant antibody in the internal fluids?

IgG

What can IgG do?

Can be bound to by Fc receptors, activate complement, cross the placenta

What differentiates the 4 IgG subclasses?

Slightly different H chains

How do we gain effector function?

Isotype switching

Monomeric IgA is found in the ____, while dimeric IgA is found in the ____

Circulation; lymphoid tissue

What is the principle antibody in bodily secretions?

IgA

______ is made the most out of any Ig isotype

Dimeric IgA

What Ig isotype is most abundant in the blood?

IgG

Dimeric IgA is synthesized locally by _____ cells in ____ and ____ glands

Plasma; Mammary and salivary

How does dimeric IgA get out into the lumen of the gut?

Poly-Ig receptor binds to the J chain which leads it into an endocytic vesicle, and then releases dimeric IgA into the lumen of the gut

What is the secretory component (SC)?

A portion of the Poly-Ig receptor that stays on the dimeric IgA

What kind of infections is IgE involved in?

Allergies, parasitic worm infections

IgE has a high affinity receptor on what kind of cells?

Mast cells

What does IgD do?

Aids IgM in recognition of pathogens and activation of B cells