Immunoglobins 1 Flashcards
what is plasma and what is serum?
plasma = cell free fluid that contains clotting factors. serum = residual fluid when blood / plasma forms a clot
what is an anti-serum?
a serum that contains antibodies that bind to a particular antigen.
what are polyclonal serums and monoclonal serums?
- polyclonal serum = serum with many different antibodies from different B cells
- monoclonal = many identical antibodies from B cell clones.
how does a naive B cell become a plasma B cell that secretes antibody?
it interacts with an antigen
what is multiple myeloma?
this is a disease in which you get over proliferative antibody production –> this disease lead to antibody discovery.
what is a hybridoma?
Researchers took mutated multiple myeloma cells and spleen cells from an immunized mouse. They fuzed these together to form what is called a hybridoma.
hybrodomas can be grown in special medium (HAT) and spew out antibody of interest.
what is HAT? what are HGPRT and TK?
HAT is a medium that hybridomas are grown on.
A - stops nucleotide synthesis
H and T are rescue functions which allow the cell to survive as long as HGPRT and TK enzymes are present.
Explain how mutant multiple myeloma cells and mouse spleen cells are created and the fuzed.
- the mouse is immunized to an antigen of interest
- the spleen creates plasma B cells that have antibodies to this antigen
- then we mutate the multiple myeloma cell so it cant have enzymes HGPRT and TK.
- then we use electrics to fuze cells
- we place in HAT medium
fuzed cells survive since mouse B cell provides HGPRT and TK.
B cells die cause they cant survive on their own
myeloma cells die since they lack enzymes to survive in HAT.
t or f, hybridoma fuzed cells are immortal and produce many antibodies
true
what is the basic monomeric structure of a antibody (4 chain heterodimer) ?
heave chain and light chain.
at tips of heavy and light chain is variable region. The rest is conserved. The base of the antibody is the Fc region which binds Fc receptors –> e.g. opsonization
once bound to an antigen, what are the three main antibody effector functions?
- neutralization
- opsonization
- complement activation
explain the three effector functions of antibodies
- neutralization –> many antibodies bind the antigen toxins and inhibit its toxicity. This will probably be eaten by a macrophage.
- opsonization –> many antibodies bind and surround an antigen. This is a signal for a macrophage to engulf it and digest it
- complement –> the bound antibodies will signal for complement proteins to come. These cause cell lysis
What is antibody-dependent cell-mediated cyto-toxicity (ADCC) (4 steps starting at infecting a host cell)
- a cell gets infected (usually by virus) and foreign proteins get expressed onto the surface of that cell
- antibodies bind these viral proteins
- the Fc regions of the antibodies gets recognized by NK cells which bind them via Fc receptors
- NK cells kill the infected cell via apoptosis
true or false, ADCC is the same thing as APC and T cells?
false. APC’s and MHC receptors is different process.
Explain in terms of variable / conserved and light/heavy chains the structure of an antibody.
from bottom to top
at the very top we have the light chain bound by disulphides to the heavy chain. At the very tip we have the VL region and the VC region.
slightly down is the CL region and the CH1 region
towards the base we now have only CH2, CH3, (CH4 in some cases) on both sides of the antibody.
what is the antibody hinge region?
middle of AB –> flexibility
What two AB’s out of GAMED do not have hinge regions?
igE and igM
think ME!!!
what two AB’s have an extra CH4 region?
igM and igE due to the lack of a hinge!
think ME!!!
some AB’s also have carbohydrates on CH2 and immunoglobulin folds, t or f
true
if proteins contain one or more regions of the same immunoglobulin fold they are…?
immunoglobulin super-families.
what are hyper-variable regions of an antibody?
extreme variable regions where Ag binding occurs
what two proteases are used to cleave antibodies?
pepsin and papain
Where does papain cleave and where does pepsin cleave?
papain makes one clean cut at the hinge region
pepsin makes a cut at the hinge region and several more at the heavy chain conserved regions
what is a Fab?
fragment antigen binding –> used after protease cleaves AB.
different AB heavy chain classes in greek letters??
Y-G = young gangster Mu = pokemon A-alpha = frat house AA Ee = young e D-delta
makes sense gamma with g, mew with M, A with alpha etc.
different AB hevay chain subclasses?
only G and A have subclasses
G –> y1-4 (gamma 1-4)
A –> alpha 1 and 2
true or false, all Ig’s have subclasses
false only G and A do
explain the light chain classes for all AB’s.
all AB’s (GAMED) all either have kappa or lambda classes.
what is the predominate class of light chain?
60% kappa
40% lambda
note: upside down Y is lambda not gamma!!
true
heavy chain = igG = gamma 1-4
light chain = GAMED = lambda
In SERUM, what is the order of percent composition of total AB’s.
G A M D E
Properties of: IgG --> Where is it found? structure? effector function? placenta?
- ubiquitous in blood / plasma and extravascular fluids
- monomeric Y shape
- effector: activates compliment, binds Fc receptors, and activates ADCC pathway.
- it CAN cross placenta
Properties of: IgA --> Where is it found? structure? effector function? placenta?
- found in most secretions such as tears, sweat, breast milk, GI tract
- dimeric in secretions BUT monomeric in serum
- major anti-bacterial agent in secretions, Mainly neutralizes them and prevents them from entering cells.
- DOES NOT ACTIVATE COMPLIMENT OR CROSS PLACENTA
has a valency of 4 in secretions
explain the formation of the secretory IgA (j chain and secretory component)
- B cell produces and secretes dimeric IgA.
- the B cell adds onto this dimer the J chain
- this goes to basal side of epithelial cell where it binds a poly-Ig receptor (PIgR)
- this transports the igA through the epithelial cell.
- it exports out the other side and the PIgR receptor stays attached and becomes what is called the secretory component.
what is the J chain and secretory component function?
J chain = holds igA monomers together
secretory component = protects dimer from proteases outside the cell
Properties of: IgM --> Where is it found? structure? effector function? placenta?
- largely confined to the blood
- in SERUM = pentamer of 5 igM’s held together by disulphide bonds and a J chain
- on B cell (BCR) = monomer
- very good compliment activator once bound to an antigen
- good aggulator since it cross links Ag binding well
- does not cross the placenta
true or false, igM was the first discovered ig
true
Does IgM have J chain? explain why if it does?
IgM in serum is a pentamer held together by disulphide bonds and a J chain. IgM lacks the hinge region (and so does igE) and also contains an additional constant heavy chain region (CH4)
true or false, the lack of hinge for IgM means lack of flexibility
false.
This would be true but other compensatory measures prevent loss of flexibility
what is IgM’s valency?
10
Properties of: IgD –>
Where is it found?
structure?
effector function?
- largely found on membrane of mature B cells
- Is NOT EXPRESSED by immature B cells
- monomer
- no known function
Properties of: IgE --> Where is it found? structure? effector function? placenta?
- is found near mast cells and basophils where it binds their Fc receptors.
- monomeric AB that slightly larger then IgG
- important in allergic reactions (works with mast cells and basophils)
- has low blood levels
- DOES NOT CROSS PLACENTA
t or f, IgG is the only antibody that significantly crosses the placenta.
true
true or false, IgE lacks a hinge region but has an extra CH4 region.
true –> so does IgM
explain how a mast cell and IgE work?
- IgE typically binds Fc-epsilon-receptors on the mast cell and chill there.
- the mast cell is filled with granules that contain histamine and other inflammation modulators.
- antigen comes by and binds the IgE and cross-linking of antigens occur.
- histamine granules released from mast cell
what are isotypes?
refers to differences in H and L chains that distinguish each class and subclass.
Alpha vs. epsilon
etc.
what are allotypes?
differences in H / L chain of same isotype.
e.g. constant regions of IgG1 and another IgG1 are slightly different.
what are idiotypes?
same isotype but they recognize different antigens. therefore the variable region of each is slightly different.
t or f, the effector functions of an AB are typically regulated through the Fc region binding to an Fc receptor on a macrophage, dendritic cell, mast cell, basophil, NK cells and more.
true
when papain cuts an antibody what fragments are left? what are they called? where it it cleaved?
- cleaves the hinge region creating three fragments
- two Fab regions where Fab = fragment antigen binding
- one Fc region
the valency is now reduced to one
when pepsin cuts an antibody what fragments are left? where is it cleaved? what are the fragments called?
- cleaves near the hinge region but the upper conserved regions and variable regions (Y) remain together
Y –> pepsin –> V + I
then the lower conserved regions such as CH2 and CH3 get cut up more.
the top region is called F(ab’)2
the bottom Fc area is called pFc’
valency is still two since variable regions are still connected.
true or false, papain cuts its AB into two Fab’s and a single pFc’.
false
papain cuts into 2 Fab’s and one Fc region
pepsin cuts into one F(ab’)2 region and one pFc’ region
