What are Isotypes?

Differences in Ig's resulting from structural varitions in heavy chains. 

Divided into 5 classes: IgA, IgG, IgM, IgD and IgE

They all have different mechanisms and may combine with the same epitope but trigger different biological responses

What are allotypes?

Form of variationg in the structure of Ig based on genetic differences between the individial. 

Usually result changes of one or two amino acids

* we both have IgG but the sequances are a litle different

What are Idiotypes?

antbodies that recognize different specific epitopes

What determines this is way at the end of the variable region

It is composed of a bunch of different idiotypes (combining sites)

Which Ig is the smallest yet most abundant?

(150,000 Da)

IgG

Which Ig can cross the placenta to help protect the baby?

IgG

Which Ig neutralizes toxins, immobilizes bacteria inhibiting their ability to invade tissues and to spread, and neutralized viruses. Ab binds to Ag’s on the various portions of the virus, keeping it from replicating

IgG

Opsonization

In this process Fab portion binds with microorganism or tumor cell, the  Fc portion binds with receptors on lymphs called natural killer cells, the IgG focuses killer cells on their target cell and destroy target with the release of cytokines. What is this called?

Antibody-Dependent, Cell-mediated Cytotoxity

Briefly explain complement and what Ig is involved in it?

  IgG’s can activate complement which Leads to release of several important chemicals which lyse antigen if the antibody is bound to the antigen

The complement system  activation is a series of cascading enzymatic events leading to the generation of specific complement components that cause opsonizatoin, phagocytosis of infectious agents and direct lysis of the invading organism among other important immunologic phenomena.

Which Ig is the first released following immunization?

IgM

Which Ig is Poor at neutralizing toxins or viruses

but excellent at fixing or activating complement to assists in the lysis of organisms?

IgM

What to elevated levels of IgM indicate?

How much does IgM weigh?

900,000 Daltons

Where are IgM's found?

Blood and lymphs

Why are IgM great agglutinators?

 These are efficient agglutinators because they can form maromolecular bridges between epitopes too distant to agglutinate otherwise

IgM's are isohemagglutinins what does this mean?

Can IgM cross the placenta?

Which Ig is found in secretions such as saliva, mucus, gastric fluid etc..?

IgA

Which Ig Does not fix complement, Is efficient against viruses,  In the presence of lysozymehas some bactericidal activity against gram negative organisms, and is good against viruses

IgA

How much does IgA weigh?

165,000 Daltons

which Ig is present in serum in low amounts short half life because of susceptibility of its long hinge to proteolytic breakdown. Function is unclear, may be to destroy B cells which have self reactive antibodies

IgD

What is the weight of IgE?

Which Ig canattach to mast cells or basophils when Ag appears, and causes cross linking of IgE which activates the cells they’re bound to which then release their histamine heparin etc.

IgE

o   (1-2 weeks after antigen exposure) no Ab seen in serum. T and B cells come into contact with Ag, to proliferate and differentiate

Ab concentration in serum increases exponentially

production and destruction of Ab are equally balanced

immune response begins to shut down. Ab concentration declines. 

During the secondary response what happens compared to primary reponse?

After Ab production ceases in primary response, memory cells are left. These mount a secondary response.

1.Lag phase is shorter.

2.Ab’s reappear in half the time, and there are many more of them.

3.secondary response is much stronger

4.Ab production continues for a longer period.

5.Class switching occurs

What is class switching?

 they are present on the surface of B cells where it serves as antigen specific receptors

also associated with a heterodimer (a-dimer made up of two similar but not identical amino acid sequences called Iga/Igb) (NOT IGA/IGB)

The heterodimer helps to activate the B-cell

they are produced by plasma cells - terminally differentiated B cells that serve as antibody factories and are housed largely within bone marrow

   Specificity is attributed to the hypervariable region (AKA complementarity-determining region, CDR)

    That region is what restricts the AB to combine only with a specific antigen

Fab, Fab, and Fc

(Fragment antigen-binding)

(Fragment Crystallizable)

Edelman later treated AB’s with mercaptoethanol (an reagent that breaks disulfide bonds) and they fell apart differently...How did they fall apart?

  His AB’s separated into 4 chains :2 light and 2 heavy, they are held together by disulfide bonds

Edelman later treated AB’s with pepsin (an enzyme that breaks down proteins in the stomach) what happened then?

  This cleaved the AB at the hinge. This results in a divalent frag referred to as F (ab) `2 [2 Fab fragments] along with several Fe frags

All species studied have two major classes of L-chains what are they?

The H-chains of all species can be divided into 5 diff classes or isotypes name them:

 The H chain gives the AB its unique biological properties; name a few..

What are immunoglobulin fold domains?

intrachain disulfide bonds that form loops within the chains and create antiparrelle B-pleated sheets of AB. 

  These domains are globular in shape each L-chain has two domains and each H-chain has 4 or 5

The AA sequence if the first domain of the light chain is highly variable from one AB to the next, what is it called?

amino acid sequances of the second domain are much more constant and are designated 

What are hinge regions?

   The hinge is composed of a short segment of AA’s between the Ch1 and Ch2 regions (IgE and IgD are exceptions in that they have long hinge regions)

The region of the heavy chain is important in that it gives flexibility to the two Fab regions, allowing them to open and close to accommodate bonding two epitopes separated by a distance

What is the variable region?

This is the region that binds to a specific antigen part. The greatest variability

the number of different  AA at a given position, occur in three areas of the L and H chains

Is it possible for 2 antibodies with different amino acid sequence have specificity to the same epitope?