Term
| What are the three main (general) properties of antibodies? |
|
Definition
1.) They are found in a number of different bodily fliuds and excretions.
2.) Chemical and Physical
3.) Immunogenic Properties |
|
|
Term
In which bodily secretions are antibodies found?
Which has teh highest concentration of Ab? |
|
Definition
Tears, mucous, saliva, feces, urine, breast milk and serum.
Serum |
|
|
Term
| What type of structure do antibodies resemble? |
|
Definition
| Glycoproteins, possessing chemical and physical properties of glycoproteins |
|
|
Term
| What is the globulin fraction of serum? |
|
Definition
| The INSOLUBLE fraction which contains ANTIBODY activity. |
|
|
Term
| What is the albumin fraction og serum? |
|
Definition
| the SOLUBLE fraction of serum...NO ANTIBODY activity. |
|
|
Term
| Where does the term Immunoglobulin (Ig) come from, in respect to Antibodies?? |
|
Definition
| The GLOBULIN fraction of serum contains antibody activity...or immunologic activity. |
|
|
Term
| What is the cause of difference fractions of whole serum being formed? |
|
Definition
| Serum proteins precipitate in different concentrations of AMMONIUM SULFATE. |
|
|
Term
| Explain the electrostatic charge of an Ab. |
|
Definition
As proteins, Ab's are chains of amino acids that possess either a net (+) or (-) or neutral charge at a certain pH.
Electrostatic charge is the neutral charge. |
|
|
Term
|
Definition
| The separation of proteins based on the net charge at certain pH's across an electrical potential. |
|
|
Term
| When you send a sample of serum through electrophoresis, how many fractions yield, and what are these fractions? |
|
Definition
(+)---Albumins-alpha-beta-gamma---(-)
1 Albumin + 3 globulin factions (a,B,Y) |
|
|
Term
| Where is most of the antibody activity on the Ab?? |
|
Definition
| In the GAMMA globulin fraction, hence the term GAMMAGLOBULIN for Ab or Ig. |
|
|
Term
| What is the relative molar mass/size of an Ab? |
|
Definition
| A range from 150 - 900 kDa |
|
|
Term
| What are the immunogenic properties of an Ab? |
|
Definition
An Ig can act as a potent immunogen in other species and can elicit Ab production against Ig-associated epitopes.
They allow for the division of In's into 5 major classes of ISOTYPES. |
|
|
Term
| What are the five major Ig isotypes or classes? |
|
Definition
1.) IgG: gamma epitopes...4 sub-isotypes in humans... IgG1,IgG2,IgG3,IgG4
2.) IgM: mu epitopes
3.) IgA: alpha epitopes...2 sub-isotypes in humans...IdA1 & IgA2.
4.) IgE: epsilon epitopes
5.) IgD: delta epitopes |
|
|
Term
| In what direction does electrophoresis go? |
|
Definition
| From negative to positive. |
|
|
Term
| Which three reagents were used to reveal the basic structure of an antibody? |
|
Definition
Mercaptoethanol (S-S reducing agent)-break disulfide bonds.
Papain - Protease
Pepsin - Protease |
|
|
Term
| What did treatment with mercaptoethanol produce? |
|
Definition
| 2 Heavy chains and 2 light chains[image] |
|
|
Term
| What did treatment of an Ab with Papain produce? |
|
Definition
| 2 Fab's and 1 Fc
Fab = fragment antigen binding
Fc = Fragment, crystallizable, and did NOT bind to an antigen.[image] |
|
|
Term
| What did treatment of Ab with Pepsin result in ? |
|
Definition
| 1 F(ab')2 and several Fc fragments.[image] |
|
|
Term
| What was the proposed model for Ig(G)Structure? |
|
Definition
4 polypeptides (2H, 2L)
2 Ag-binding sites (each is a Fab)
Each Fab fragmen associated with 1L chain
Fc fragment forms BASE of "Y" sheped molecule |
|
|
Term
| What is special about the L chain molecules in Humans? |
|
Definition
There are 2 of them present: KAPPA and LAMBDA.
But only 1 type of L chain is found per Ig molecule. Either κ or λ, NOT BOTH!!
In Humans, 60% are kappa and 40% are lambda. |
|
|
Term
| Serum contains a ______ mixture of Ig...explain |
|
Definition
| Heterogeneous...the Ig's have similar structure, BUT with a wide range of specificities available (variability). |
|
|
Term
| The variability of Ig's in serum ia part of the ____ structure of Ig. |
|
Definition
|
|
Term
| What part of the Ig was examined to see HOW variability is achieved. |
|
Definition
| Examining amino acid sequences on H & L chains. |
|
|
Term
| How many regions or domains can the Light chain be divided into? |
|
Definition
| 2: 50% constant(CL) and 50% variable (VL) region |
|
|
Term
| Describe the CONSTANT region of the LIGHT chain. |
|
Definition
| The Light chain can be either Kappa or Lambda. All light chains have the SAME CONSTANT region. It is near the C-Terminal...COOH. |
|
|
Term
| Describe the VARIABLE region of the LIGHT chain. |
|
Definition
| The VARIABLE region changes, its variable from L chain to L chain and from kappa chain to lambda chain. It is near the N-terminal, 50% of L chain sequence. |
|
|
Term
| Howmany regions or domains are HEAVY chain sequences usually divided into? |
|
Definition
|
|
Term
| Describe the CONSTANT region of the HEAVY chain. |
|
Definition
| It is constant for EACH ISOTPYE (so all ε chains of IgE have the same constant region, but a diff. constant region thatn IgG) |
|
|
Term
| Describe the VARIABLE region of teh HEAVY chain. |
|
Definition
| Variable from H chain to H chain...N-terminal is 20-205% of H chian sequence. |
|
|
Term
| VL and VH possess WHAT two general features?? |
|
Definition
1) Complementary Determining Region(CDR)
2) Framework Regions |
|
|
Term
|
Definition
| Complementary Determining Regions: Located on variable regions of H&L chains. Here, variability is essentially LIMITED to specific regions composed of amino acid sequences whose chemical groups directly interact with an EPITOPE on an Ag molecule - hypervariable regions. |
|
|
Term
|
Definition
Complementary Determining Regions: Located on VARIABLE regions of H&L chains. Here, variability is essentially LIMITED to specific regions composed of amino acid sequences whose chemical groups directly interact with an EPITOPE on an Ag molecule - hypervariable regions.
Basically....CDRs are the antigen-binding regions of antibodies. |
|
|
Term
| What are hypervariable regions? |
|
Definition
|
|
Term
| How many CDRs are there on each variable region? |
|
Definition
| There are THREE CDRs on each VARIABLE region of both L and H chain. |
|
|
Term
| What are FRAMEWORK regions? |
|
Definition
Relatively constant sequences w/in variable regions.
Important in aligning CRDs in correct spatial orientation w/in Ag-binding site (ABS). |
|
|
Term
| What is the main structural characteristic of Constant regions? CH and CL? |
|
Definition
| H chain constant regions and L chain constant regions contain "repeated" sequences of amino acids termed DOMAINS!!...forming a structural motif known as the.....immunoglobulin-fold (Ig-fold). |
|
|
Term
| How are the VL & VH similar to the constant regions? |
|
Definition
| REMEMBER: The VL & VH sharea similar Ig-fold structural motif. |
|
|
Term
| Describe the domains that are present among the different isotypes. |
|
Definition
IgG,IgA & IgD have 3 CH domains(CH1,CH2,CH3).
IgE & IgM have 4 CH domains (CH1,CH2,CH3,CH4) |
|
|
Term
| What makes up the antigen binding site for each Fab? |
|
Definition
| VH and VL domains pair to form the Ab-binding site. |
|
|
Term
| How do the domains pair in a simple IgG antibody |
|
Definition
CH1 - CL
CH2 - CH2
CH3 - CH3
CH4 - CH4 in IgE & IgM |
|
|
Term
| What is the Hinge region? |
|
Definition
Fab fragments ("arms") of some Ig isotypes exhibit free range of movement about the Fc fragment("base") of the molecule... appear HINGED
Connects the Fab arms to Fc |
|
|
Term
| Which isotypes have SUB isotypes? |
|
Definition
|
|
Term
| Which isotypes have a hinge region? |
|
Definition
| each IgG subisotype, IgS subisotype, adn IgD |
|
|
Term
| Which Isotypes do not have a hinge region? |
|
Definition
|
|
Term
| Does the 3-dimensional structure of Ig's change between isotypes? |
|
Definition
| No, the overall 3D structure of an Ig monomer is fairly consistent among different isotypes. |
|
|
Term
| What provides variability to the ABS? |
|
Definition
| CDRs w/in V-regions of both H & L chains. |
|
|
Term
| Describe the 3D regions of a typical Ig. |
|
Definition
| A typical Ig has 3 globular regions...2 Fab and 1 Fc. |
|
|
Term
| Describe the Fab of a normal Ig. |
|
Definition
It contains the: ABS (VL-VH) and CL-Ch pairing.
The variable regions of H and L chain combine to form a deep cleft lined w/ amino acids of CDRs to compose teh ABS. |
|
|
Term
| What pairs together in the Fc? |
|
Definition
CH2 - CH2 via carbohydrate I think.
CH3 - CH3
CH4 - CH4 (in IgE and IgM) |
|
|
Term
| Which Ig Isotype is the most abundant in the serum? |
|
Definition
| IgG = 80% of total serum immunoglobulin. |
|
|
Term
| What does an IgG isotype consist of? |
|
Definition
2 γ HEAVY chains
2 λ or κ LIGHT chains |
|
|
Term
| How many subisotypes are there for IgG, and why are they numbered as so? |
|
Definition
FOUR IgG sub-classes.
Distinguished by differences in gamma-chain constant region sequenced .
They are numbered according to their decreasing average serum concentrations. i.e. IgG1 in in the highest concentration in Serum.
Vary based on size of hinge region and the no. and position of the interchain disulfide bond betweern heavy chains. |
|
|
Term
| Why are the subtle differences in amino acid sequences between IgG sub-isotypes important? |
|
Definition
| They affect the biological activity of the molecule. |
|
|
Term
| Describe the biological activity of IgG1, 3, and 4. |
|
Definition
| They readily cross teh placenta and play an important role in protecting the developing fetus. |
|
|
Term
| Describe the role of IgG sub-types in terms of activating the complement system. |
|
Definition
IgG-3 is the most effective complement activator, followed by IgG-1.
IgG-2 is less efficient, and IgG-4 is not able to activate complement at all!
Complement activator: IgG 3 > 1 > 2 > 4 |
|
|
Term
| Describe the role of IgG sub-types towards opsonization. |
|
Definition
IgG-1 & 3 bing with HIGH affinity to Fc receptors on PHAGOCYTIC cells and this promote opsonization.
IgG-4 has an intermediate affinity for Fc receptors.
IgG-2 has an extremely low affinity.
Opsonin: IgG 1=3 > 4 > 2 |
|
|
Term
| I what 2 forms are IgG's found? |
|
Definition
|
|
Term
Where are IgG's found when in MEMBRANE form?
What are their functions? |
|
Definition
They are found present on some MEMORY B CELLS. An Additional transmembrane domain anchors into the membrane.
Functions as an Ag-component of BCR. |
|
|
Term
| What are the functions of IgG's while in SERUM form? |
|
Definition
1) They are able to move in&out of serum and tissues and can cross placenta providing protection for infant early in life.
2) Major effector molecule (Ab) of LATE PRIMARY AND SECONDARY HUMORAL responses.
3) Major OPSONINS
4) Neutralize Ag (i.e. toxins)
5) Activate (fix) complement system, primarily IgG1 and 3. |
|
|
Term
| What does each monoer of IgM consist of? |
|
Definition
2 LIGHT chains (κ or λ)
2 HEAVY chains (μ) |
|
|
Term
| Which IgG is the 3rd highest in Ig concentration in the human SERUM? |
|
Definition
|
|
Term
| What are the two forms that an IgM can be found in? |
|
Definition
Serum form as a PENTAMER
Membrane form as a MONOMERIC IgM |
|
|
Term
| How are the 5 monomers held together in the IgM pentamer? |
|
Definition
Held by interchain DISULFIDE BONDS (S-S).
One end of the chain is attached to the other by a J-chain polypeptide - Forming a circle. Each side is S-S bonded to the J chain. |
|
|
Term
| How many ABS's are present PER monomer of an Ig generally? |
|
Definition
|
|
Term
| How many Antigen molecules deos a typical PENTAMER IgM bind to? and WHY? |
|
Definition
The pentamer binds to 5-10 Ag, not: 2x5=10...
because of STEARIC hindrance. |
|
|
Term
| What are the main functions of IgM? |
|
Definition
1.) 1st Ab produced during teh primary humoral response.
2.) Early neutralization and agglutination of Antigen.
3.) Very efficient at activating ("fixing") complement |
|
|
Term
| What is a benefit of the large size of the pentamer IgM? |
|
Definition
| Its large size limits its movement out of serum but can undergo MUCOSAL TRANSPORT. |
|
|
Term
| In what form is the IgM when it is a pentamer? |
|
Definition
Serum form....
Pentamer is in serum! |
|
|
Term
In what form is an IgM when it is membrane-bound?
Describe IgM in its membrane form. |
|
Definition
Monomeric form.
Possesses additional transmembrane region arrached to Cμ4 domain (on heavy chain) that anchors it in membrane of NAIVE mature B cells. |
|
|
Term
| What is the 2nd most abundant isotype in human Serum?? |
|
Definition
|
|
Term
What are the 2 sub-isotypes of IgA??
What chains are IgA's composed of? |
|
Definition
IgA1 and IgA2
Each IgA monomer compoesed of 2 light chains (κ or λ) and 2 heavy chains (α1 or α2) |
|
|
Term
| What forms are IgA's found in? |
|
Definition
1: membrane form (as a monomer)
2: serum form (mostly as a monomer, but sometimes as a dimer or tetramer)
3: SECRETORY form (as a DIMER: 2IgA monomers joined by S-Sbonding to a J-chain, same as J-chain from IgM pentamer) |
|
|
Term
| Where are membraneous IgA's found? |
|
Definition
| on SOME memory B cells as part of the BCR. |
|
|
Term
| Explain the process of how IgA's are secreted? |
|
Definition
Secreted by plasma cells as a DIMER, in submucosa. They bind to the BASAL side of the mucosal epithelial cell, to a POLY-Ig RECEPTOR. Dimeric IgA:poly-IgReceptor binding promotes endocytic transport to lumenal side of epithelial cell where poly-Ig receptor is cleaved at its base.
Part stays w/IgA and forms the SECRETORY COMPONENT of secretory IgA(SIgA). |
|
|
Term
| What components make up the secretory IgA (SIgA)? |
|
Definition
| Part of the poly-Ig receptor from the basal side of the mucosal epithelial cell, and the whole dimeric IgA. |
|
|
Term
| Extra facts about secretion of Ig's |
|
Definition
- The endocytosis involved in transporting IgA from the plasma cell is RECEPTOR-MEDIATED endocytosis.
- The poly-Ig receptor is enzymatically cleaved adn becomes the secretory component.
- The Secretory IgA is released into the mucous secretions.
- The secretory component masks sites susceptible to protease cleaveage in the hinge region of secretory IgA, allowing the polymeric molecule to live linger in the protease-rich mucous. |
|
|
Term
| Extra facts about secretion of Ig's |
|
Definition
- Pentameric IgM is also transported into mucous secretions by the same mechanism as IgA.
- However, secretion of IgM accounts for a much lower % of Ab in the mucous secretions than does IgA.
- The poly-Ig receptor interacts with the J-chain of both polymeric IgA and IgM antibodies. |
|
|
Term
| What is the purpose of the secretory component of secreted IgA?? |
|
Definition
| To mask the site that are vulnerable to protease cleavage in the hinge region of secretory IgA. This allows the poymeric IgA to exist longer in the protease-rich environment of the mucous. |
|
|
Term
| What are the main functions of IgA's? |
|
Definition
1) Major Isotype in bodily secretions-mucis, tears, saliva, breast milk, GI.
2) Blocks adherance of microbes to receptors on host cell.
3) agglutinates microbes facilitating their shedding w/in mucus.
4) In BREAST MILK, provides important GI IMMUNITY FOR INFANT. |
|
|
Term
| Which two isotypes are found in very low concentrations in Human Serum? |
|
Definition
|
|
Term
| What chains comprise the IgE isotype? |
|
Definition
2 light chains (kappa & lambda)
2 heavy chains (epsilon)
possesses a 4th CH domain!! |
|
|
Term
| How many forms is IgE found? |
|
Definition
| 2: membrane and serum form |
|
|
Term
| What is special about IgE in its serum form? |
|
Definition
| It is mainly found in tissues on MAST CELLS or BASOPHILS, rather than free in serum. Explains why IgE has such low concentrations in the serum. |
|
|
Term
| What are the main functions of IgE?? |
|
Definition
1) defense against certani prasites...URT & GI immunity.
2) Key role in type I hypersensitivities (ALERGIES)...UNIQUE sites in Fc region BIND STRONGLY to HIGH AFFINITY RECEPTORS ON MAST CELLS AND BASOPHILS. |
|
|
Term
| What chains is IgD composed of ? |
|
Definition
2 light (kappa or lambda) chains
2 heavy (DELTA) chains |
|
|
Term
| Why is IgD susceptibleto protase digestion?? |
|
Definition
| Because it has a hinge region like IgG and IgA. IgA when secreted has secretory component which prevents digestion though. |
|
|
Term
| What is special about IgD in its membrane form?? |
|
Definition
It is a monomer found on the membranes of MATURE B CELLS----
It acts as an Ag receptor w/ mIgM on NAIVE MATURE Ag-reactive B CELLs.
Remember: IgM is the 1st Ab produced during the primary HUMORAL response!! |
|
|
Term
| Isotypes reflect differences between _________. |
|
Definition
Species.
ISOTYPES ARE COMMON TO ALL MEMBERS OF A SPECIES. |
|
|
Term
| Where are isotype epitopes located on an Ig and what are they called? |
|
Definition
| Located within teh CONSTANT,HEAVY... and CONSTANT, LIGHT regions and are called ISOTYPIC DETERMINANTS. |
|
|
Term
|
Definition
They are encoded by different genes...reflect gene amplifications and mutations,...create additional epitopes associated with CH or CL domains.
Common to all members of a particular species. |
|
|
Term
| Allotypes reflect differences between ________. |
|
Definition
| Members of the same species. |
|
|
Term
|
Definition
A group of potential epitopes that are located w/in the CH or CL (allotypic determinants).
They are expressed in some but not all individuals of the SAME species.
Genetically determined (ALLELIC) VARIATIONS in genes encoding C regions of L&H chains.
Different allotypic determinants represent differences in 1-4 amino acids that are encoded by different alleles of the same gene. |
|
|
Term
| What happens when you inject the antibodies of 1 person into another member of the SAME SPECIES? |
|
Definition
| Antibody to allotypic determinants can be made because person B carries different allotypic determinants than person A. |
|
|
Term
| People have 2 copies of each of their genes, leading to....... |
|
Definition
HOMOzygous individuals - single allotype for each Ig isotype or sub-isotype
HETEROzygous individuals - 2 possible allotypes for each Ib(sub)Isotype; so theoretically, 1/2 of any Ig (sub)isotype will be of 1 allotype and 1/2 will be of the other. |
|
|
Term
|
Definition
| Differences between epitope-specific Ig within the same individual producing them. All idiotypes are the same within the SAME IG...but different when you switch to another IG that is still in the same person. |
|
|
Term
| Idiotypes are immunogenic within the _____ the Ig. |
|
Definition
|
|
Term
| Where are idiotypes located? |
|
Definition
They are unique amino acid sequences of the VARIABLE heavy and light domains of a given antibody.
They can be associated with ABS sometimes combining to be the actual antigen binding site. Some comprise variable-region sequences that are OUTSIDE of the binding site. |
|
|
Term
| Remember this about idiotypes: |
|
Definition
| B/c the antibodies produced by individual B cells derived from the same clone have identical variable-region sequences, they all have the SAME IDIOTYPE. |
|
|
Term
| Explain what the Ig SUPERFAMILY is? |
|
Definition
| Ig H & L chains have structural features found in several other membrane proteins that play some role in the immune responses suggesting they evolved form a common ancestral gene. |
|
|
Term
| What are some common feature that are shared among the IG superfamily? |
|
Definition
1) They have 1 or more Ig-FOLD STRUCTURAL DOMAINS.
2) Proteins that posses Ig-fold domains are members of the Ig superfamily eventhough they have diff. functions and are not genetically linked. |
|
|
Term
| What members are included in the Ig Superfamily?? |
|
Definition
Ig-Heavy Chain
Ig-Light Chain
Ig-alpha/Ig-beta of BCR
TCR
CD4
CD8
CD3 subunits
MHC I
MHC II
poly-Ig Receptor
Other cell adhesion molecules (VCAM-1, ICAM-1 /-2) |
|
|
