B cells and Antibodies Flashcards
definition of antibodies (imunoglobulins)
proteins made and secreted to bind with antigens. Once bound, helps inactivate/clear out microbial (or non-microbial) agent
Ig structure
2 identical heavy chains and 2 identical light chains
light chains isotypes and their frequnecy
kappa (60%), lambda (40%)
heavy chain isotypes
α - IgA 1, 2 δ - IgD γ - IgG 1, 2, 3, 4 ε - IgE μ - IgM
FAB
fragment antigen binding: portion of antibody that binds antigen
FAB is produced by digestion of Ig with what enzyme?
Papain
Fc
Fragment crystallizable: effector function of Ig, binds with other things that have an Fc receptor
Fc contains which portion of the antibody molecule?
C-terminal portion
F(ab’2) and produced by which enzyme
Bivalent FAB fragment, produced by pepsin
Ig molecule consists of how many FAB and Fc fragments?
2 FAB and 1 Fc fragment
how many hypervariable regions (CDRs) are on each light and heavy chain? How many in total on an Ig?
3 on light chain, 3 on heavy chain, a total of six
Basis of specificity for antigen
HV regions = CDRs (complementarity determining regions)
What makes up one FAB region?
VL, VH
CL1 CH1
How many variable (heavy and light) domains are on an Ig?
On variable heavy, one variable light on each half of Ig, so in total, 2 VH and 2 VL
How many Constant light domains are on each Ig?
One CL on each side of Ig, so a total of 2 CL domains
How many constant heavy domains are there on each Ig? Which two Igs are an exception
3 constant heavy domains on each side, so 6 in total. IgM and IgE can have a fourth constant heavy domain
less variable regions aligning hypervariable regions that provide structural integrity to variable domains
framework residues
Isotype
constant regions of heavy/light chains
idiotype
antibodies with different variable domains
Igs that are complement activators
IgG and IgM
B-cell membrane receptors (mature cell)
IgM and IgD
First antibody during immune response
IgM
The only antibody produced by immature B-cell
IgM
2 fates of IgM and structural form for both
- plasma membrane bound, serves as B cell receptor for antigen or B cell activator (monomer)
- secreted from plasma, potent activator of compliment classical pathway (pentamer)
Second isotype of Ig produced
IgD
very similar to IgM but contains different Fc portion
IgD
the “glue” that hold a pentamer Ig together
J-chain
Ig with highest serum concentration
IgG
5 important properties of IgG
1) longest half life (much more stable, resists degradation) ~23 days
2) the only Ig that can cross placenta to provide fetus immunity
3) can perform ADCC
4) acts as an opsonin
5) compliment activator
In opsonization, what party of the antibody binds to the bacteria? what part of the antibody binds to the phagocyte?
FAB binds to antigen of bacteria, FC site binds to an Fc (gamma) receptor on on phagocyte
What receptor is needed for IgG to perform ADCC?
CD16
Why is IgG a less efficient compliment pathway activator than IgM?
IgM is secreted as a pentamer, while IgG is a monomer, so its needs multiple monomers
“Prepare to ingest”
Opsonin
Ig involved in mucosal immunity
IgA
IgA is secrete as what structure?
Dimer
Which antibody does not activate compliment pathway? Way?
IgA, dont’ want a huge inflammatory response in GI tract
Mild, neutralizing antibody
IgA
This Ig is mostly found on epithelial cell surfaces and binds to bacterial toxin to prevent epithelial damage
IgA
least common Ig, small amounts in circulation
IgE
Ig for allergic reactions, hypersensitivity reactions, and parasitic infections
IgE
This Ig is mainly found in lungs, skin, and mucous membranes
IgE
Mast cells have these receptors fo IgE
Fc epsilon receptors
Crosslinking of antibodies and antigen on mast cell causes what to occur and what to be released?
Degranulation of mast cells, release of histamine
binds to antigen first, then triggers opsonization
mABs (3 properties)
monoclonal antibodies
- targets only a single polypeptide chain
- no variation between antibodies produced
- highly controllable
Rituximab
mAB, marker on B cells, used in treatment of lymphoma and leukemia
Infliximab
Anti-TNF (tumor necrosis factors, cause apoptosis)
hence why need to be careful with monoclonal antibodies. need these things as inflammatory mediator
Monoclonal antibodies bind to the same _______ of antigen, which serves to detect and purify a substance
epitope
Monoclonal antibodies work only because B-cells operate through this type of system
Clonal selection (each B-cell has a specific antibody as a cell surface receptor, and only B cells, which are antigen specific, can secrete antibodies. Produce antibody of a specific type which we can isolate and capture)
What type of interaction occurs between an antibody and antigen
noncovalent
Reaction between an antibody and an antigen that differs from the immunogen
Cross-reactivity
Type B blood type have what type of antigens
B antigens
Persons who are Type AB what what antigens
A and B antigens
What antigens to persons with Type O have
have neither A nor B antigens
The serum of people with Type A blood have what kind of antibodies
Antibodies against Type B antigens
Type AB blood type have what kind of antibodies
Neither antibody
Type O blood type have what antibodies
antibodies against A and B
Universal Donor
Type O
Universal recipients
Type AB (lack antibodies against A or B antigens
True or False: A person with type O blood may receive from a person with Type B blood
False (a person with type O blood has anti-B antibodies which would react against the type B antigen found on the red cells of type B blood
When Type B blood is given to a person with type A blood, antigen from the _____ reacts with anti-B antibody in the ____ (donor or recipient)
Donor, recipient
Blood group antigens are a system of antigens that are ____ in nature
glycolipid
What is the core glycan anchored in the erythrocyte membrane? Everyone has this, and will not react to this
Gal NAc–Gal–X
|
Fucose
Gal NAc =N-acetylated galactosamine
Gal= galactose
X= the R group that is different in each blood type
X group for O
nothing
Gal NAc–Gal
|
Fucose
X group for A
Gal NAc–Gal–GalNAc
|
Fucose
X group for B
Gal NAc–Gal–Gal
|
Fucose
immunogenicity
ability of a particular substance to induce an immune response (i.e. antigen or epitope)
What elicits the blood group antibody reaction?
GI flora (commensal bacteria) generate proteins/sugars/etc that are foreign to humans. Immunse system response to these antigens, but the bacteria never leave the GI tract. Bacteria are harmless within the GI lumen. But antibodies are ready in case any bacteria does cross epithelium
GI bacterial biproducts have structura similarity to
blood groups
True or false: Individuals do not make specific antibodies against bacteria in the gut that are similar to their own blood type
True. They do not.
Lipids and nucleic acids alone are (strong/weak) generators of antibodies
Weak. generate more robust response as lipoprotein or nucleoprotein, which will be processed by an APC
If a lipoprotein is degraded by APC, which part does Th cell recognize? Which part does B cell recognize? (but relies on Th still)
Helper T cell recognizes the peptide. The B cell can recognize the lipid or carb part, but need Th cell from protein to help it recognize the lipid or carb.
