Antibody Flashcards
What are the 2 fragments of antibody?
What are their functions?
Fragment Ag binding ( Fab )
-> Antigen binding ==?
Fragment crystallizable ( Fc )
-> Complement activation
-> FcR binding ( Fragment crystallizable Receptor )
Is it true that antibody is a tetramer?
Yes
What is the hinge in antibody?
What is its function?
Its between Fab & Fc
-> Allows opening / closing & twisting of Fab for better antigen binding
What do the following do to antibodies?
-> Pepsin digestion
-> Mercaptoethanol reduction
-> Papain digestion
Pepsin digestion
-> Cuts right below hinge
- -> F(ab)2 x1
Mercaptoethanol reduction
-> Breaks every disulfur bond
- -> H chain x2
- -> L chain x2
Papain
-> Cuts right above hinge
- -> Fab x2
- -> Fc x1
What does CDR 1, 2, 3 spikes in variability?
CDRs are the sites for antigen binding
-> Higher variability = more diversity for different antigen
What is the other region other than CDR region on an antibody?
What is its function?
Framework region
-> provides structural support
Does the top part of the variable segment or the bottom part of constant segment carries NH+ / COO- on an antibody?
Top part of V segment
-> NH+
Bottom part pf C segment
-> COO-
What are the 3 components of BCR?
BCR
-> mIg
-> CD79 ( Ig - alpha + Ig - beta ) x2
Is CD79 ( Ig - alpha / Ig - beta ) a B cell specific marker for cell identification?
YEET
Which 2 antibody classes are found on BCR membrane?
IgM & IgD
Which 2 antibody classes have an additional domain on their heavy chain C segment?
IgM, IgE
Are immune complex reversible?
why?
Immune complex: The state of Ag - Ab
Yes
-> Non covalent bonds = reversible
Which antibody class is mainly in mucosal transport?
IgA
Which antibody class is responsible for acute allergies?
IgE
Which antibody class dominates other classes in terms of number in circulation?
Why?
IgG
-> Higher half - life
Is IgM or IgD better at activating complements?
IgM
A woman & her fetus is infected by bacteria, what is the order for antibodies to cross the placenta and save DA BABY?
IgG
-> Only IgG can cross placenta
Match the following <:
mIgM
sIgM Monomer
IgD
IgG Dimers
IgE
IgA Pentamer
Monomer
-> mIgM
-> IgD
-> IgG
-> IgE
Dimer
-> IgA
Pentamer
-> sIgM
We learned about TCR - CD3
What about BCR - CD??
CD79
Explain first contact & second contact of allergy using the example of pollen
First contact with antigen ( Low level immune response )
-> CD79 activates naive B cell => Plasma cell
- -> Secretion of IgE
- - -> IgE attaches to Mast cells
Second contact with antigen ( Supaa high level immune response )
-> IgE on Mast cells grabs antigen
- -> Activation on Mast cell
- - -> Releases granules containing Histamine
- - - -> Allergic reaction
Where is pIgR found?
What is its purpose?
Mucosal epithelium
Function
-> To transport polymeric Ig across the mucosal epithelium to the mucosal surface
-> To offer protection & stability to polymeric Ig
What are the steps for secreting IgA from plasma cell in submucosa to the lumen?
Binding of dimeric IgA by pIgR
-> Endocytosis of IgA into mucosal epithelium in cytosolic vesicle
- -> Enzymatic cleavage of pIgR
- - -> Secretory IgA + pIgR
Secretion & composition of colostrum & milk
Match the predominates antibody class ( IgG, IgA ) to the following
Ruminants colostrum
Ruminants milk
Non ruminants colostrum
Non ruminants milk
Primates colostrum
Primates milk
Ruminants
-> IgG
Non ruminants colostrum
-> IgG
Non ruminant milk
-> IgA
Primates
-> IgA
What are the 4 reasons why antibodies can be absorbed and not be digested in newborn’s stomach?
Low protease activity
Trypsin inhibitors in colostrum
Special FcRs ( FcRn ) in intestinal epithelium
Permeability in intestine is highest
-> Declines after 6hrs
- -> FcRn+ => FcRn-
Which body parts immunity do colostrum & milk provide in Ruminants ?
Colostrum
-> System immunity
Milk
-> Intestinal immunity
Why aren’t vaccines useful for newborn?
Maternal antibody will neutralize antigen
-> B cell of newborn will not be activated
What did IgY evolve into in mammals?
IgG
IgE
Which antibody class is in egg white & egg yolk?
Albumin ( Egg white )
- IgA
Egg yolk
- IgY
What is the 3 reasons why IgY is so shitty?
Poor in
-> Opsonization
-> Complement activation
-> Activating allergic response
Why does IgY still exists then?
Extremely diverse environment meaning that not being too sensitive might actually be healthy for the animal
-> Being able to identify antigen without activating strong immunity is nice
What is an opsonin?
Any molecules that targets an antigen for immune responses
What is opsonization of antibody?
Allow binding of FcR of phagocytic cells to Fc for easier phagocytosis
What is the classic pathway of complement activation?
Activation of C1 - complex
What is the 3 antibody - mediated effector functions?
Opsonization
Activation of complement
ADCC
What is isotypic determinants?
Difference in C segment of heavy chain
-> Antibody classes
C region determinants collectively determines the antibody class within a specices
What is allotypic determinants?
Subtle a.a. difference in the same class
-> Different strain
- -> usually subtle, but might affect interactions with effector cells
Typically subtle
-> Still contributes to the general diversity of immunity between individuals in a species
What is idiotypic determinants ( Idiotopes )?
Difference in V segment
-> Different antibodies ( essentially what we have been learning about diversity of antibodies )
Difference in antibody within an individual
-> Sum of the individual idiotopes = idiotype of antibody
What are the 3 reason for B cell anergy?
Downregulation of mIgM
-> more than 5% of mIgM are occupied by monomeric soluble Ag
- -> Only mIgM
- - -> Not mIgD
B cell encountering antigen without the help of T cell
B cell unresponsive to antigen even with the help of T cell
Are there more IgM / IgG produced in first contact / second contact?
First contact
-> IgM
Second contact
-> IgG
What are the order for affinity ( Weakest to strongest ) for antibody class ?
IgM , IgD < IgG < IgE < IgA
What are the 3 coreceptors (CD) for B cell activation?
CD81
CD21
CD19
What is the coreceptor for B cell inhibitor?
CD22
What does bcl - 2 do?
Prevents apoptosis ( Inhibits apoptosis )
What does bax do?
Opposes bcl - 2 ( Promotes apoptosis )
What does Fas do?
Induces apoptosis ( Initiates apoptosis )
What is Idiotypic regulation?
When there is an immune response
-> Both idiotypic & anti idiotypic antibodies are produced
- -> Anti idiotypic antibodies can either inhibit / enhance idiotypic antibodies
- - -> This ensures the immune response is proportionate to the threat
- - - -> Prevent prolonged / excessive immune response
- - - -> Prevent inadequate immune response
What is polyclonal antibodies?
Mix of antibodies produced by difference plasma cell
Recognizes various epitopes
Produced naturally by immune system to combat infections
Polyclonal antibodies can be derived from serum of animals
What is monoclonal antibodies?
Identical antibodies with exact same VDJC segments
Highly specific & recognizing only 1 epitope
Produced by hybridoma cells
-> Plasma cells + Myeloma cells
(Myeloma cells : cancer cell originated from plasma cell)
