antibodies are??
targeted effector proteins
what are the three sources of antigen diversity?
genetic recombination
junctional diversity
somatic hypermutation
after negative and positive selection the B cells is considered
mature and leave the bone marrow and head to secondary lymphoid tissues
where do antibodies bind on antigens?
on the epitope of the antigen
1 antibody to 1 epitope
effector functions of antibodies
receptors in B cells and Granulocytes
neutralize
opsonize
signaling
the heavy chain determines what?
the isotype and thus the antibody class
what are the five antibody classes?
IgA IgG IgM IgD IgE
the heavy chain has a proportionally small or large variable region?
small because there is no hypermutation that occurs here
what are the two isotypes of the small chains?
kappa and lambda
heavy chain characterisitics
determines class receptor interaction (Fc portion) proportionally small variable region binds antigen
light chain characteristics
binds antigen
proportionally large variable region
two isotypes
T/F each isotype can bind the same antigen and the same epitope
true because the variable region doesn’t change in class switching
what antibodies interact with j chians
IgM pentameric
IgA dimeric
what antibody is good at neutralization and diffusion and opsonization into extravascular tissues?
IgGs
also cross placenta
what antibody is good at activating the complement?
IgM (mostly in the blood) and IgG
what antibody sensitizes basophils
IgD
what antibody is good at transporting across epithelium?
IgA
what antibody is good at sensitizing mast cells?
IgE
antibody variable regions do what?
bind antigens
antibodies can bind to what?
polysaccharides, globular proteins, lipids
what is the difference between linear and discontinuous epitopes?
linear the recognition site is one after another
- discontinuous the recognition sites are separated but due to structure are close
- linear are used for antigen testing
T/F antigens can different epitopes on their surface as well as repeated copies of epitopes on their surface?
true
antibody structure facilitates what?
function
what is the first antibody to be expression on a B cell?
IgM then an IgD
Gene rearrangement occurs where?
bone marrow
*as well as junctional diversity
once the B cell is in the secondary lymphoid tissue what happens?
somatic hypermutation and isotype switching
what are the three portions of the variable region of the heavy chain?
variable
diversity
joining
what are the two portions of the variable region of the light chain?
variable and joining
T/F each loci for the light chain and heavy chain are located on different chromosomes?
true
kappa light is on chrom 2
lambda light is on chrom 22
heavy is on chrom 14
what is the sequence of recombination?
the joining and diversity region are spliced together
- the the DJ region is spliced to variable region
- segments are randomly paired
what does the RAG complex do?
randomly pairs gene segments
order of pair gene segmentation
- Vh-Dh-Jh-> Vh-DJh
- Vh-DJh-> VDJh (heavy chain)
- VL-JL-> VJL
* remember heavy chain is first
what is junctional diversity?
2nd place of antibody diversity
- *-when you are pairing a junctional with a diversity region you are adding nucleotides to the sequence and thus altering the DNA sequence thus changing protein structure
- this occurs on light and heavy chains between the variable, diverse, and junction or joining regions
Can a single B cell express all antibody isotypes?
yes
is isotype switching permanent
yes with the acception of IgM and IgD
why is isotype swithcing not permanent with IgM and IgD?
because the termination sequence is after the conserved regions of both IgM and IgD
-this means that at an mRNA step either IgM or IgD conserved regions are cut giving both IgM and IgD due to alternate splicing
why are IgD important in B cell development?
they bind with Igalpha and Igbeta which allows for signaling
upon antigen activation of the B cell what happens?
antibody secretion
somatic hypermutation and class switching
**only in mature B cells
what are the three sources of antibody diversity?
Genetic recombination
Junctional diversity
Somatic hypermutation
what does polyclonal mean?
multiple antibodies targeted against the same antigen
what does monoclonal mean?
a single antibody targeted against a single antigen
isotype switching occurs within the light or heavy chain?
heavy chain
remember the heavy chain determines isotype**
