Antibodies Part 1 Flashcards
In antibodies, each chain is composed of domains helpd together by what?
intrachain disulfide bonds
What are the domains of the light chain? heavy chain?
light: one variable and one constant
heavy: on variable and three constant
In IgG, what pushes the CH2 domains of the heavy chains out a little bit to help them interact with components of the complement system?
a patch of carbohydrates
IgM forms a ___amer,
pentamer
What’s the chain holding the globulin units together in IgM?
J chains
What is IgM particularly good at?
activating complement
What’s an important distinction about IgA (besides the fact that it’s a dimer of globulin units)?
It has a secretory component that will keep it from being degraded by the secretions in the mucous membranes
Where are IgD located?
on the membranes on B cells - act as the BCR
Are the heavy chains always identical in antibodies? the light chains?
They are identical within the same antibody, yes.
What are the 5 kinds of heavy chains that define the class of natibody?
gamma, alpha, mu, epsilon, and delta
What are the two varieties of light chains?
kappa and lambda
During class switching (like going from making IgM to IgA for example), what changes: the light chains or heavy chains?
only the heavy chains switch - the light chains sill stay the same
The area at the N terminal of the antibody is called what domain?
the variable domain
Aminoa acid sequence variability is not distributed uniformly along the variable domain; most of the variability is in 3 areas called the _______ regions or _____-determining regions since they make the actual antigen binding site
hypervariable regions
complementarity-determining regions
What does valence refer to?
the number of antigenic determinants (epitopes) an antibody molecule can theoretically bind
What’s the valence of IgG? IgA? IgM? Fab? isolated VL or VH?
IgG = 2 IgA = 4 IgM = 10 Fab = 1 Vl or VH = 0 (it takes the combo of the two chains
What is the concentration of the 5 classes of antibodies in the serum?
IgG = 1000 mg/dL IgA= 200 mg/dL IgM = 100 mg/dL !gD = 5 mg/dL IgE = 0.02 mg/dL
What antibody is the main one in blood and tissue fluids?
IgG
What can IgG do?
It can neutralize toxins and blood-borne iruses, binds bacteria and facilitates their destruction by activating complment and by binding them to phagocytic cells
Where is IgA primarily located?
in secretions (does pretty much the same thing as IgG)
What is the first antibody to appear in the serum after immunization?
IgM
Although it is very efficient at activating complement, why is it less adept than IgG at other functions?
It does not get into tissue fluids very efficiently, nor is it bound efficiently by phagocytic cells
What type of hypersensitivity is associated with and IgE mediated process?
type 1 hypersensitivity (allergies)
Althouhg IgE is associated with allergies, what is it’s true importance for the immune system?
resistance to worms and other parasites
When an IgG or IgM antibody binds antigen, there can be a change in the angle between the two Fab pieces which causes a bulging of the structure of the Fc part so that….
- they can bind to phagocytic cells which have receptors for the altered Fc of IgG
- Clq (first component of complement) can bind to the Fc and be activated
Why is IgM so much better than IgG at activating complement?
Because IgM is a pentamer, it only needs one IgM molecule to activate complement, while IgG will have to have multiple binding close together on the same surface
Describe how the immunoglobulin genes are organized in the chromosome
They’re organized from 5’ to 3’: V (variable regions), then D (differentiating regions), then J (joining regions)
Describe the general mechanism by which the variable regions undergo gene rearrangement.
in the nucleus of the cell, the V, D, and J domains can be recombined at random
for the heavy chains you’ll get 1 V, 1 D and 1 J eventually linked together (everything else is spliced) formign a functional VDJ gene
For the light chains it’s similar, but you only have a V and J (no D)
What enzymatic complex is needed for recombination to occur?
RAG synatpic complex
How many subclasses of antibodies are there? What are they?
there are ten
IgG1, IgG2, IgG3, IgG4 IgA1, IgA2 IgM1, IgM2 IgD IgE
The allelic differences in the sequences of immunoglobulins between individuals are called what?
allotypes
Each antibody will have its own unique combining region which we call the…
idiotype
An antibody that actually recognizes the idiotype of another antibody is called what?
an anti-idiotype
