Antibody Structure & Function: Key Terms for Biology Study

Draw an Ig molecule. Include V region, C region, hypervariable region, L chain, H chain, F(ab)'2, Fc, and antigen binding site.

What three genes code for the variable region of the H chain?

VDJ

The ______ gene codes for the constant region of the H chain.

C

VDJ genes are joined together through ______.

V(D)J recombinase

The heavy chain genes are rearranged ______ light chain genes.

before

What is the order of heavy chain gene rearrangement?

D-J first, then add V, then add C

What is the order of light chain gene rearrangement?

V-J, then add C

Because of alternative splicing, both ______ and ______ can be expressed on a mature B cell.

VDJ-µ (IgM), VDJ-δ (IgD)

Either ______ or ______ light chain isotype can be chosen for each antibody, not both.

kappa, lambda

Isotype switching is unique to the ______ region locus.

H chain C

Isotype switching occurs with ______.

antigen stimulation

______ and ______ are both requires for isotype switching.

cytokines (IFN-y, IL-4). activation-induced cytidine deaminase (AID)

Mature B cells express both ______ and ______.

IgM, IgD

After ______ exposure, enzymes cut segments of the gene sequence.

antigen

Whichever ______ chain gene segment is left (and first) is expressed.

heavy

Antibodies are essential in ______ immune response.

humoral immunity is

Abs can be ______ or ______.

membrane bound (BCR), secreted (plasma cells)

There are 2 ______ and 2 ______ chains of an Ab.

heavy, light

There are ______ bonds within an Ab.

disulfide

Papain cleaves Abs just above the hinge region to create what segments?

2(Fab) + Fc

Pepsin cleaves Abs to create what segments?

1 F(ab')2, 2 identical L chains, 2 identical H chains

What region distinguishes the 5 Ab isotypes?

The constant region

The nature of the ______ chain dictates properties of that Ab.

heavy

What are the two isotypes of light chains?

kappa and lambda

Isotype means Ab ______.

class

Allotype is the ______ Ab difference between 2 people.

whole

Idiotype is the Ab ______ difference between 2 people.

binding site

What is the most abundant Ig?

IgG

IgG is important in ______ immune response.

secondary

IgG has subclasses ______, in order of abundance in serum.

IgG1-4

IgG can cross the ______ and ______.

placenta (not IgG2), tissues

IgG causes ______ and ______ of antigen.

agglutination, precipitates

What are the biological functions of IgG?

- Opsonization

- Neutralization of toxins and viruses

- Activation of complement

- Antibody-dependent cell-mediated cytotoxicity (ADCC)

When the first protein in complement cascade (C1q) encounters IgG, the ______ complement pathway is initiated.

classical

IgM is the first class produced by the ______.

fetus

IgM is ______ in shape. How many antigen binding sites does it have?

pentameric

10

IgM functions in the ______ immune response.

primary

IgM can also be ______ on B cell surfaces.

monoemric

What is the first Ig present during primary immune response?

IgM

When IgM dies down, ______ increases.

IgG

Eventually, IgG ______.

dies down

During secondary response, ______ shows up first, in the same amount as in the primary response.

IgM

When IgM dies out during secondary response, ______ comes in very high amounts and stays high.

IgG

This allows for...

Lessened symptoms, quicker alleviation of disease

At birth, ______ levels decrease and ______ levels increase.

Maternal IgG

IgM/G/A

IgM is the first line of defense for ______ immunity.

neonatal

IgM has the best ______.

complement fixation

IgM is the best isotype at ______.

agglutinating

Why is IgM the best at all these?

Because of its increased number of binding sites due to its pentameric shape

IgA is found in ______.

secretions

IgA protects against ______ and ______ infections.

respiratory, GI

IgA is a monomer in ______, but has no function.

serum

IgA is a ______ in secretions.

dimer

IgA has ______ and ______ component when dimerized in secretions.

J chain, secretory

IgA is the most common Ab ______.

deficiency

IgE is important in ______.

type I hypersensitivity (allergy)

IgE binds to Fc receptors on what cells?

Mast cells, basophils

IgE increases during ______ infection.

parasitic

IgE can be responsible for the transfer of ______ between individuals.

allergy

The role of IgD is unknown, but it may play a role in ______ activation.

B cell

IgD is a receptor on naive ______.

B cells

Which Igs activate classical complement?

IgG (1,2,3), IgM

Which Igs can cross the placenta?

IgG

Which Igs are present on the membrane of mature B cells?

IgM, IgD

Which Igs are important in mucosal transport?

IgA, IgM

What Igs induce mast cell degranulation?

IgE

What contributes to the diversity and large number of Abs?

- Germline diversity (inherited genes)

- Combinational diversity (VDJ recombination)

- Junctional diversity (imprecise VDJ joining)

- Somatic hypermutation

- Class switching

Somatic hypermutation is a mutation that occurs in the V region that results in the creation of ______ Abs

variant

Some of these variant Abs have a higher affinity for their ______.

antigen

Monoclonal antibodies are a collection of ______ that interact with a single antigen site.

identical antibodies

mAbs are created through the combination of what three things? What does this create?

B cells, myeloma cells

Hybridoma

The hybridomas then undergo ______, individual screening, then mAbs are produced by hybridoma clones.

ELISE screening

mAbs are essential for what things within the clinical lab?

In vitro diagnostics, pregnancy, rapid tests, ELISA, flow cytometry, autoimmune disease treatment

RA and Crohn's disease can be treated with a mAb towards the cytokine ______.

TNFa

IgM heavy chain gene

μ

IgG heavy chain gene

γ

IgD heavy chain gene

δ

IgA heavy chain gene

α

IgE heavy chain gene

ε

Which immunoglobulins have a J chain?

IgM and IgA

Through allelic exclusion, only one ______ is kept for each Ab.

light chain (kappa or lambda)

If kappa rearrangement is successful, then ______ is not rearranged.

lambda

If kappa rearrangement fails, ______ rearrangement occurs.

lambda