59-Antibody Structure and Function

Question 1

antigen receptors

Answer 1

on surface of lymphocytes
B cell receptors
T cell receptors
many different receptors to recognize unlimited number of foreign Ags
clonically expressed-1 unique Ag receptor per lymphocyte clone

Question 2

Surface BCR and soluble Ab molecules

Answer 2

identical except small transmembrane sequence on C terminal end

Question 3

function of BCR

Answer 3

recognition of antigen

initiates signal transduction using CD79a/b to start intracellular signaling

Question 4

CD79

Answer 4

needed for BCR to start intracellular signalling

Question 5

structure of Ab

Answer 5

2 heavy chains
2 light chains
hinge region for torsion
disulfide bonds to hold molecules together
N linked carb chains linked to heavy chain for 3D structure and half life

Question 6

variable region

Answer 6

heavy-VDJ
light-VJ
form antigen binding pocket, 2 identical pockets that bind identical antigens

Question 7

constant region

Answer 7

no recombination, ensure structural integrity

H chain is for key effector functions

Question 8

Fab region

Answer 8

Ag binding, 2 Fab regions=Fab2, bind 2 identical antigens

Question 9

Fc region

Answer 9

below hinge region, heavy chain constant region

effector functions

Question 10

Fab

Answer 10

cleave above hinge

Question 11

Fc

Answer 11

cleave above hinge

Question 12

Fab2

Answer 12

cleave below hinge

Question 13

hypervariability regions

Answer 13

3 regions in both heavy and light, “complementarity determining regions”
1 and 2 and encoded in DNA
3 is recombination of VDJ or VJ

Question 14

CDR

Answer 14

complementarity determining regions, variability in heavy and light chains
proximal in tertiary structure and form Ag binding pocket

Question 15

epitope

Answer 15

small segment of Ag bound by Ag binding pocket, non covalent interactions

Question 16

what can TCRs recognize vs BCR/Ag

Answer 16

TCR-peptides, require MHC

BCR/Ag-lipid, carb, protein, nucleic acid, interact with epitopes on surface of pathogens, do not require MHC

Question 17

end product of B cell activation

Answer 17

cell that secretes Abs (soluble version of BCR) that recognize pathogen epitope and bind then recruite innate immunity to mediate destruction

Question 18

Ab isotypes

Answer 18

defined by heavy chain constant region
5 isotopes encoded by loci
IgM, G, A, E, D

Question 19

subclasses of Ab

Answer 19

IgG-4

IgA-2

Question 20

IgM structure

Answer 20

4 constant regions, no hinge
large and inflexible=only in blood
secreted as pentamer-10 binding sites

Question 21

antibody that is a pentamer

Answer 21

IgM

Question 22

IgM functions

Answer 22

neutralization
agglutination
complement activation

Question 23

neutralization Abs

Answer 23

IgM, IgG, IgA

Question 24

agglutination Abs

Answer 24

IgM, IgG, IgA

Question 25

complement activation Abs

Answer 25

IgM, IgG

Question 26

IgG structure

Answer 26

3 constant regions with hinge secreted as monomer-2 binding sites most abundant found in blood and tissues

Question 27

antibody that is a monomer

Answer 27

IgG, IgA in blood, IgE

Question 28

IgG functions

Answer 28

``` neutralization agglutiniation complement activation opsonization/phagocytosis Ab dependent cellular cytotoxicity transplacental transfer ```

Question 29

opsonization/phagocytosis Abs

Answer 29

IgG, IgA

Question 30

Ab dependent cellular cytotoxicity Abs

Answer 30

IgG

Question 31

passive immunity to fetus through placenta Abs

Answer 31

IgG

Question 32

IgA structure

Answer 32

3 constant regions with hinge monomer in blood dimer in mucosal secretions

Question 33

antibody that is a dimer

Answer 33

IgA in mucosal secretions

Question 34

IgA functions

Answer 34

neutralization agglutination opsonization/phagocytosis immunity in breast milk

Question 35

immunity in breast milk Abs

Answer 35

IgA

Question 36

IgE structure

Answer 36

4 constant regions, no hinge region | monomer

Question 37

IgE function

Answer 37

bound to mast cells with high affinity | mediate type 1 hypersensitivity reaction/ allergic reaction

Question 38

allergic reaction Abs

Answer 38

IgE

Question 39

IgD structure

Answer 39

3 constant regions with hinge, rarely secretes, used as BCR on naive B cells

Question 40

no hinge

Answer 40

IgM, IgE

Question 41

agglutination

Answer 41

traps microbes in a complex impair movement, attachment, replication, colony formation IgM, G, A- lots of binding sites or hinge with torsion

Question 42

neutralization

Answer 42

prevent pathogens and toxins from binding to their host | IgM, G, A

Question 43

Complement activation-Classical pathway

Answer 43

Ab binding to Ag makes immune complex formation allosteric change in Fc to bind C1q to start complement cascade, Use IgM, G recruit C4 and 2, activation of C3 convertase cleave C3, C3a inflammation, C3b opsinization recruit and cleave C5, C5a inflammation C5b recruits C6, 7, 8, 9 to form MAC, create channel and lyse

Question 44

Opsonization

Answer 44

coating of pathogen with ligand recognized by phagocytic cells IgG, IgA, C3b

Question 45

Phagocytic cell receptors

Answer 45

Fc receptor bind antibodies C3b receptor bind C3b 4 IgG Fc receptors, 1 IgA Fc receptor, 4 C3b receptor

Question 46

natural killer cells

Answer 46

IgG Fc receptors bind IgG Abs with their Fc tail provide specifficity to NK cells to recognize and bind Ags on target cells kill using proteolytic enzymes and inducing apoptosis

Question 47

maternal IgG

Answer 47

to fetus through circulation can cause disease hemolytic disease of newborns IgG aBs against Rh blood group, give RhoGAM to Rh- moms

Question 48

maternal IgA

Answer 48

in mothers milk | protect baby's gut