antibody strx and fxn Flashcards
immunoglobulins
same as antibody; they are membrane bound and soluble receptors
epitope is? made of?
antigenic determinant; part of an antigen that is the binding site for an antibody; usually a carb or peptide
vaccine antigen
can be a single molecule, or can be a more complex particle
examples of a vaccine antigen
DTaP and HPV vaccine. can be a viral capsid that is empty on the inside
antibody can recognize
linear, folded, or denatured antigen/epitope proteins.
hapten
small molecules that can don’t induce an immune response ONLY when BOUND to a carrier molecule
example of a hapten
penicillin which disrupts the cell wall of bacteria which can make the cell wall bind to a RBC or something else; the immune system says NO and can get rid of it.
how many chains in an Ab/immunoglobulin?
2 light, 5 heavy
most common immunoglobulin?
IgG
Where is the N terminus/Cterminus in an Immunoglobulin
both of the N terminuses are at the tip of the Y; the C is at the base
special features of an immunoglobulin?
disulfide bond between two heavy chains in the hinge region
where is the antigen-binding site?
in the variable region
what does papain do?
it cleaves the disulfide bond and you get the separation of the Y into three parts: two identicle FAB molecules and one crystallizable base
pepsin does?
cleaves below the hinge region; there is no functionality of this molecule, but the Fab half can still bind to an antigen
what does the hinge region do?
it allows the two arms of the Ab molecule to have some flexibility; this way the Ab can bind to epitopes with different steric configurations
down side of hinge region?
this is where the Ab is more linear and therefore it is more subject to proteolysis
More specific Ab configuration
the heavy chain has three constant domains and one variable domain
structure of Fab?
made of Beta sheets that are linked together with a disulfide bond (think sandwich with a toothpick in it)
why is the folding of Ab important
by folding in the pleat the parts of the protein that are more variable are exposed to make a unique Ab to create antibodies with different specificities
what does the constant domain do?
determines the function and the class of the Ig. (remember that the constant domain is the heavy chain base)
each constant domain can combine with?
a lambda or kappa light chain
hinge regions are present in
igG, igD, igA; M and E have an extra heavy chain section on them.
allotypic differences defn.
differences between two IgG molecules; eg. like one from mom and one from dad
idiotypic differences defn.
differences between individual Ab molecules that will recognize different epitopes; their variable domain is different so they can recognize different stuff
Binding strength is determined by?
the fit. better fit means a stronger binding. its non-covalent bonding
affinity=
strength of interaction between the epitope and ONE antigen-binding site; there can be more than one binding site
avidity=
the SUM of the strength of binding between an epitope and antigen binding site
crossreactivity
sometimes two different Ab can share a same epitope;
monoclonal antibodies
immortalized plasma cells usually mouse derived; you take B cells with a specific antigen and fuse them with tumor cells that are “immortal”; select for the cells that produce the antibody that you are interested in
polyclonal antibodies
purified from serum of immunized animals (usually goats or rabbits) eg. ebola serum from recovered patients and give it to those with ebola
chimeric Ab
part human, part mouse; -ximab
humanized Ab
95% human, 5% mouse; -zumab
human Ab
100% human; -umab; best for treatments; this type is less likely to develop anti-antibody response
immunoassays. rank their specificity
radioimmunoassays and Elisa are most sensitive.
RIA, ELISA > agglutination > precipitation
what is precipitation immunoassay
when the antibody and antigen complex; ideally, you want an equal amount of Ab to Ag. that gives you the most amount of precipitation.
blood type
the antibodies for this are IgM. they don’t cross the placental barrier
coombs test
uses anti-human immunoglobulin to cross link the RBCs
rhesus factor
IgG antibodies that CAN cross the placental barrier
ELISA test for HIV
can use to test for HIV; coat the wells with antigen and ad the serum sample. use chemistry to see if the person developed antibodies for HIV
western blot for HIV
used as a secondary test for someone who had a positive HIV elisa test; test for proteins that are made by HIV
immunofluroescence
take a biopsy and rinse it with a fluorescent Ab for that virus. if it lights up, its positive
flow cytometry
take blood and mix with a fluroescent Ab for a cell type; you can run it through fluoroscopy and you can tell how many of cell type X you have present in a blood sample.
flow cytometry and HIV/AIDS
great way to track the progression of AIDS; count how many CD4+ cells are present in the patient infected with HIV
three loci that code for ___?
genes for the lambda(light chain), kappa(light chain); and heavy chain
diversity gene segements are only in
heavy chain
how do you regulate the chain genes?
recombination signal sequences that consist of spacers;
how specifically is the spacer important in gene selection
a 23 gene spacer can ONLY recombine with a 12 gene spacer; therefore a 23 spacer cannNOT combine with a 23 spacer
V(D)J recombinase
these enzymes are used to splice out parts of the Ab gene; RAG is one of the enzymes what works in the V(D)J group
TdT does?
enzyme that adds nucleotides to joining regions of the D and J gene when it links back together.
mutation in TdT
can cause a frameshift mutation of the coding sequence between the D and J regions
what are the factors that work together to create overall Ab diversity
the different chains (kappa, lambda, heavy), imprecise joining, and nucleotide addition (with TDT enzyme)
how could a naive mature B cell express more than one Ig type?
it is from alternative splicing; it just splices out different constant domains so it can co-express IgM and IgD. this is NOT isotype switching
what do Ig alpha and Ig beta do?
when a B cell binds to an antigen, it does a conformation change and the Ig pair sends an intracellular signal to create a kinase cascade
what doe b cells do after activation
they secrete antibodies, they do isotype switching, and somatic mutation(additional diversity)
coombs tests
for IgG; uses hemagluttination
