Unit 7 Antibodies I Structure and Function

Question 1

term antibodies is used in context of

Answer 1

antigens eg an antibody to antigen such as bacterium

Question 2

term Ig is used when

Answer 2

to emphasize antibodies are globulin proteins produced by immune system

Question 3

Ig are made up of

Answer 3

one pair of identical heavy chains and light chains

Question 4

each chain is divided into

Answer 4

constant (C) and variable (V) regioons

Question 5

what is variable region

Answer 5

high degree of variations among Ig. where the ABS is located (specificity)

Question 6

what is constant region

Answer 6

same/constant among class of Ig (eg all IgM have same heavy chain constant region)

Question 7

constant region is associated with

Answer 7

biological fn that could be unique to particular Ig class

Question 8

light chains are further divided into

Answer 8

2 domains VL and CL

Question 9

heavy chains are further divided into

Answer 9

4 domains Vh Ch1 Ch2 Ch3

Question 10

eg the antigen binding site can be represented as

Answer 10

VL + Vh

Question 11

enzyme papain cleaves Ig molecule into 3 fragments:

Answer 11

2 Fab and 1 Fc

Question 12

composition of the 2 Fab fragments

Answer 12

VL Cl Vh and CH1 domains

Question 13

composition of 1 Fc fragment

Answer 13

Ch2 and Ch3

Question 14

enzyme pepsin cleaves Ig into

Answer 14

1 F(ab’)2 fragment (contains intact ABS) and 1 pFc’ fragment

Question 15

constant region could contain (3)

Answer 15

1. receptors for complement
2. site that interacts w/transport protein in placenta to antibodies (IgG only)
3. receptors for macrophages, granulocytes or mast cells

Question 16

IgG (and C3b) can act as _ to do what

Answer 16

opsonin. help macrophage capture pathogen more easily

Question 17

Ig are classified into 5 classes according to

Answer 17

constant region of heavy chains

Question 18

Ig classes

Answer 18

IgG (four subclasses) IgA (2)

IgM, IgD, IgE

Question 19

what is hypervariable region

Answer 19

variable regions of light (VL) and heavy chains (Vh) which contain ABS

Question 20

features of IgG

Answer 20

most common in blood, major Ab of 2nd immune response, opsonin, when complexed w/Ag activates classical complement pathway, agglutinate antigen, pass through placenta passive immunity

Question 21

IgG through placenta is what type of immunity

Answer 21

naturally acquired passive immunity

Question 22

features of IgA

Answer 22

in seromucous secretions, saliva colostrum etc

Question 23

structure of secretion IgA

Answer 23

2 IgA joined (dimer) together by joining chain

Question 24

list benefits of secretory IgA

Answer 24

naturally acquired passive. lower incidence of GI and respiratory infections among breastfed

Question 25

features of IgM

Answer 25

pentamer. activate classical complement, first Ig that appears in primary immune response. effective agglutinating Ab

Question 26

IgM as a monomer found on

Answer 26

membrane of mature B lymphocytes. acts as cell surface receptors for antigens

Question 27

why is IgM so effective an agglutinating

Answer 27

multple ABS allows attachment of many antigen

Question 28

features of IgD

Answer 28

cell surface receptors for antigens on B cells

Question 29

features of IgE

Answer 29

scarce in peripheral blood, w/eosinophils defend against parasitic worms, w/basophil or mast cell responsible for allergy

Question 30

how is in vitro test of Type 1 allergy performed

Answer 30

checking serum level of total IgE or allergen specific IgE

Question 31

effect of eosinophil binding to Fc of IgE

Answer 31

frustrated phagocytosis against big worm ->release granules of destructive enzymes

Question 32

major fn of antibody (humoral) immune response (5)

Answer 32

neutralization, opsonization, activation of classical complement, agglutination, antibody dependent cell mediated cytotoxicity ADCC

Question 33

what is neutralization (anti-adhesion)

Answer 33

block attachment of microorganism to susceptible cells (viral). block binding of microbial products such as toxins to target cells

Question 34

what is opsonization

Answer 34

phagocytes are more effective in capturing extracellular Ag when coat with IgG

Question 35

activation of classical complement by forming of Ab-Ag complex leads to

Answer 35

chemotaxis, inflammation, opsonization, and formation of MAC

Question 36

agglutination is helpful how

Answer 36

increased number of antigens can be phagocytized when agglutinated

Question 37

what is antibody dep. cell med. cytotoxicity ADCC

Answer 37

PMNs, macrophages, NK cells have receptors for constant region of Ab. when bind to Ab attached to org can kill them more effectively

Question 38

primary vs secondary humoral response

Answer 38

primary generated following first encounter of antigen. secondary generated after in subsequent exposures

Question 39

what is lag or latent phase

Answer 39

stage where no antibody is detected in blood/plasma

Question 40

what is seroconverson

Answer 40

from sero -ive (no Ab detected) to sero +ive (Ab detected)

Question 41

testing during lag/latent phase gives what results

Answer 41

false -ive. infected but pathogen-specific Ab not detectable

Question 42

what is log phase

Answer 42

antibody titre (level) increases exp

Question 43

what is paired sera

Answer 43

serum taken during acute (illness/lag) and convalescent (recovered/log) phase to see evidence of infection

Question 44

what is plateau phase

Answer 44

when antibody titre reaches max and stabalizes

Question 45

what is decline phase

Answer 45

Ab is catabolized and returns to lower level