Antibody Flashcards
(48 cards)
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-
