Antibodies

Question 1

Describe basic structure of monomeric antibody. specify 3 forms other than for monomeric

Answer 1

there are 2 light chains covalently linked to 2 heavy chains. Each region has a variable region (n terminal) and a constant region (c terminal). Dimer, trimeric and pentameric

Question 2

Name 2 different types of light chain constant regions

Answer 2

Kappa and Lambda. 2 kappa can join together or 2 lambda, but never 1 of each. - kappa is more common. demonstrates allotypy (similiar to alleles for genes). Kappa chain allotypes=Km

Question 3

List 5 antibody isotypes. Specify greek name and symbol of the heacy chain constant regions that defines each type

Answer 3

IgG (gamma)
IgE (Epsilon)
IgD (delta)
IgA (Alpha)
IgM (Mu)

Question 4

Define the term subclass as it relates to IgG and IgA

Answer 4

IgG has different variations in individuals (IgG1,2,3,4)

IgA has different variations in individuals (IgA1,2)

Question 5

Define the term allotype as it relates to IgG and IgA

Answer 5

allotypes are differences between individuals

Question 6

Regarding antibodies: Explain what is meant by bifunctional molecule, biological activity and specificity

Answer 6

bifunctional molecule=antigen binding ability and biological activity region.
biological activity= Fc region mediates the atibody effector function
specificity=variable region has amino acid variations, and recognize specific antigen and then binds to it. hyper variable regions are called complementary determining regions (CDR). these forms paratopes which bind epitopes via hydrophobic/ionic components

Question 7

Specifiy 3 names for sites within the variable region that bind the epitope

Answer 7

CDR, Fab, Fv bind the epitope

Question 8

Define Avidity, the type of interaction, the # of identical binding sites on a monomeric antibody

Answer 8

avidity=describes the overall binding energy of the interactions the strength. Affinity is how easy/strength the binding is.
Digest with papain: 3 molecules: 2 copies of Fab (2Fab/2F(ab)) and 1 Fc (won’t bind)
Digest with Pepsin: 1 molecule with 2 binding sites (Fab2)
the Fc fragment is degraded

Question 9

IgE

Answer 9

monomeric, sparse in serum b/c its binds to FcER on mast/basophils. Multivalent antigen binding, causes crosslinking of FcER which will relase inflammatory and vasoactive mediators from preformed granules

Question 10

IgD

Answer 10

only exists as membrane bound form on naive B cells. Low levels indicates cell death. Not much else is known

Question 11

IgG

Answer 11

found on monocytes, macrophages, neutrophils, and Bcells (very low affinity of B cell). T1/2= about 1 month. comprises 75% of total Ig. All subtypes can cross the placenta. IgG1=highest conc. IgG3=shortest t1/2 of a week, most effective activator of compliment. IgG4= lowest conc. does not activate compliment and does not bind to Fc gamma R

Question 12

IgG Elimination of microbes

Answer 12

Opsinization: phagocytosis triggered by Fc binding, bound to pathogen to Fc gamma R
ADCC: antibody dependent cell cytotoxicity, NK cells express low affinity Fc gamma R which interacts with IgG bound target cell. This causes the release of cytotoxic molecules to destroy it.
Complement: cascade of molecules/complex to destroy cells
Neutralization: viruses or other toxins neutralized when IgG antibody binds to the antigen to inhibits its ability to bind to a receptor.

Question 13

IgA

Answer 13

monomer, dimer, trimer connected by J chain. Subtypes A1, A2. t1/2=1 week. the major antibody of milk and clostrum. Found in gut, tears, sweat, saliva. Present on all external surfaces that aren’t skin. Infants that breast feed have moms immunity to gut pathogens. Secreted as dimeric for. It binds to a secretory component ad activates alternative compliment pathway.

Question 14

IgM

Answer 14

monomeric when membrane bound. Pentomeric when secreted from plasma cell. J chain holds it all together. 10 binding sites but due to steric hinderance not all are bound at the same time. 15% of total Ig are IgM. Expressed on immature B cells and mature B cells. t1/2=1week. activates compliment pathway=increase phagocytosis and lysis of bacteria.

Question 15

IgM Blood

Answer 15

isohemagglutinins. A, B, O. A type has A antigens on cell surface and makes Anti B. O has know antigens on surface and makes Anti A and Anti B. O is universal Donor because it has no antigens to be detected. AB is universla recipient because it has both antigens and there is no anti A/B. Accepts it all.

Question 16

monoclonal antibody

Answer 16

Antibodies from a single clone of antibody secreting plasma cell

Question 17

Polyclonal antibody

Answer 17

Antibodies from many clones of antibody secreting plasma cells.

Question 18

cross linking

Answer 18

when 1 antigen is bound by 2 antibodies

Question 19

Cross reactivity

Answer 19

when antibodies that can bind to 1 epitope on antigen, can bind to another similar epitope on differnet antigen.

Question 20

Idiotope

Answer 20

Antigenic determinants from hypervariable region

Question 21

Anti isotypic antibodies

Answer 21

antigenic determinants from constant region

Question 22

Rh factor

Answer 22

antigen on the RBC that about 85% of population has. Rh+. Problems occur when mom is Rh- and baby is Rh+. When the baby is born, blood mixes and mom makes antiRh. So next baby that is Rh+ will be attacked when the IgG crosses the placenta. this causes jaundice/anemia. Erythroblastosis fetalis, hemolytic disease of the newborn.

Question 23

explain how antibodies can function as antigens. Explain the rationale for injecting animals with human antibodies

Answer 23

antibodies are proteins. you can have antibodies bind to variable or constant regions of other antibodies.