Antibody Structure and Function

Question 1

what are antibodies

Answer 1

specifically induced serum glycoproteins which recognize antigens

Question 2

where are antibody molecules found

Answer 2

• circulate in the blood
• present in body secretions
• found on the surface of B cells (act as antigen-spec receptors)

Question 3

how can antibodies inactivate pathogens

Answer 3

-directly inactivate pathogens following interaction w/ relevant antigenic determinants that they express

Question 4

what can antibodies stimulate

Answer 4

non-specific host effector mechanisms such as complement proteisn and cytotoxic cells
-can also act as opsonins

Question 5

which end of antibodies recognize antigenic determinants (epitopes) on the antigen

Answer 5

amino terminal end of the molec contains the antigen binding site which recognizes epitopes

Question 6

which end of ab binds various effector cells and molecules

Answer 6

carboxy terminal portion

Question 7

what were the major bands that were revealed when serum proteins were separated into fractions

Answer 7

albumin
alpha
beta
gamma globulins

Question 8

which fraction is the only one capable of passively transferring humoral immunity from an immunized donor to a naive recipient

Answer 8

gamma globulin fraction

known as passive immunization or vaccination

Question 9

how are gamma globulin and albumin different

Answer 9

gamma is not a homogenous protein, it consists of many diff molec having the same basic structural features but diff aa sequences

Question 10

what is the molecular weight of a typical gamma globulin

Answer 10

150,000 daltons

Question 11

what make up the basic immunologic structure

Answer 11

2 identical heavy chains of 50,000

2 light chains of 25,000 daltons

Question 12

what is papain

Answer 12

an enzyme that produces fragments of approx equal molec weight but of diff molec composition when digested with immunoglobulin

Question 13

what are fab fragments

Answer 13

fragments that retain their ability to bind antigen after being liberated by papain digestion
“fragments w/ antigen binding activity)

Question 14

what is an fc fragment

Answer 14

crystallizable fragment

Question 15

what is pepsin

Answer 15

an enzyme when digusted liberates a single fragment of approx 100,000 daltons which exhibi antigen binding capability

Question 16

why is f(ab)2 referred to as being bivalent

Answer 16

it can bind antigen at 2 sites

Question 17

what is f(ab)2 held together by

Answer 17

disulfide bond

Question 18

what do multiple myeloma tumor cells produce

Answer 18

a single homogeneous innunoglobulin w/ one aa sequence (confirming clonal selection theory)

Question 19

patients with multiple myeloma secrete what

Answer 19

prodigious amounts homogeneous antibody, which facilitate the sequencing of the molec

Question 20

what are immunogloblulin molec held together by

Answer 20

interchain disulfide bonds within each of the protein chains
non-covalent, ionic, and hydrophobic bonds

Question 21

what are the 2 classes of light chaisn in humans

Answer 21

kappa and lambda

-each antibody molec has either kappa or lambda chains, not both

Question 22

how many classes of heavy chains are there in humans

Answer 22

10

Question 23

what part of the light and heavy chain is responsible for antigen recognition (fab portion)

Answer 23

amino terminal half of the light chain

amino terminal quarter of the heavy chain

Question 24

where are the variable (V) regions located at

Answer 24

the end of the chain

-in the amino terminal

Question 25

where are the C regions located at

Answer 25

close to the hinge

Question 26

what are the hypervariable regions

Answer 26

-highly divergent stretched w/in the V regions

Question 27

what form the antigen-binding cleft

Answer 27

hypervariable regions of apposed heavy and light chains of each Fab fragment

Question 28

where is the hinged region, what does it do

Answer 28

in the heavy chains affects the flexibility of movement of Fab portions -in some it can allow both fab portions to bind antigen, rather than just 1, which increases the strength of ab attachment

Question 29

where are the constant regions of immunoglobulin on the heavy and light chains

Answer 29

3/4 of the heavy chains from the carboxy end and similar half of the light chains

Question 30

where are complx carbs located on the chains

Answer 30

heavy chains in the Fc region

Question 31

what involves the rearrangement of the germinline DNA endocding the heavy chain

Answer 31

first steps in B cell development

Question 32

what are the major classes of antibody isotypes

Answer 32

igG, A, M, E, D "Gamed"

Question 33

which isotypes can be subdivded into closely related subclasses "subtypes"

Answer 33

igA and igG

Question 34

what creates the different isotpes

Answer 34

sequence of aa in the heavy chain make the difference

Question 35

which is the first isotype that is released by plasma cells

Answer 35

igM

Question 36

which is the most effective complement-activating antibody isotype, why

Answer 36

igM | =secreted form found in serum is a pentamer (consits of 5 igM monomers => 10 antigen binding sites

Question 37

which isotypes are found on virgin B cells (havent seen antigen yet)

Answer 37

igM and igD

Question 38

how do you form secreted igM

Answer 38

monomers are polymerized in the cell by a process requiring the production of a separate protein called the J chain, which links and stabilizes them

Question 39

which is the first immunoglobulin produced during the immune response

Answer 39

igM

Question 40

what is the primary functino of igD

Answer 40

rare found in serum | to act as a second antigen receptor

Question 41

what is the major immunoglobulin class found in serum

Answer 41

igG

Question 42

what is the role of igG

Answer 42

activates complement | act as B cell surface antigen-receptors on memory B cells (cells that are produced after initial antigen stimulation)

Question 43

where is igA found

Answer 43

relatively low concentrations in the serum but is abundant in body fluids like intestinal and mucous secretions, saliva, tears, and colostrum

Question 44

what ist he only isotype that can be transported across epithelial cell boundaries

Answer 44

igA

Question 45

which isotype is critical for host defense againt organisms that cn invade the body

Answer 45

igA

Question 46

which isotype binds to polymeric immunoglobulin receptors on the basolateral membranes of lacrimal acinar cells

Answer 46

igA

Question 47

what does the secretory componene tsreve as

Answer 47

to protect igA from degradation by microbial proteases produced ex ocular surface bacteria

Question 48

what is immune repertoire

Answer 48

the established pool of immunoglobulin V regions that is present in an indiv

Question 49

what are the 3 mech by which the immune system generates an enormous variety of diff V regions on immuno heavy and light chains

Answer 49

1. multiple genes: large # of separte genes which encodes one V region domain 2. somatic (genetic) mutation: V region mutates during B cell devleopment to produce diff genes in diff B cell clones 3. somatic recombination: # of gene segments recombine to join the main part of the V regino gene. results in protein containing elements coded for by diff gene segments

Question 50

what are the antimicrobial functions of secretory igA

Answer 50

1. agglutination (clumps) 2. preventino of microbial attachment 3. inactivation of bacterial enzymes and toxins 4. antibody-dependent cell mediated cytotoxicity 5. opsinization (igA acts as opsonin)

Question 51

which isotype are good at complement activation | which is not

Answer 51

igG and igM | igA is not good

Question 52

how can antigens enter the body

Answer 52

- from the gut through M cells (delivers antigen directly to underlying immune cells) - through more common enterocytes (ep cells taht line the gut)

Question 53

who described monoclonal ab

Answer 53

georges kohler | cesar milstein

Question 54

what are hybridomas

Answer 54

immortilized cells produced with monoclonal antibodies of pre-determined specificity

Question 55

what are the applications of monoclonal antibody tech

Answer 55

1. identificatino of phenotypic markers of cell types 2. purified isolation of cell types with unique markers 3. purification of antigens 4. immunodiagnosis 5. functional analysis of cell-surface and secreted molec 6. immunotherapy and immunosuppresion