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OD2-Immunology > Antibody Structure and Function > Flashcards

Antibody Structure and Function Flashcards

1
Q

what are antibodies

A

specifically induced serum glycoproteins which recognize antigens

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2
Q

where are antibody molecules found

A
  • circulate in the blood
  • present in body secretions
  • found on the surface of B cells (act as antigen-spec receptors)
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3
Q

how can antibodies inactivate pathogens

A

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

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4
Q

what can antibodies stimulate

A

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

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5
Q

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

A

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

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6
Q

which end of ab binds various effector cells and molecules

A

carboxy terminal portion

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7
Q

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

A

albumin
alpha
beta
gamma globulins

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8
Q

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

A

gamma globulin fraction

known as passive immunization or vaccination

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9
Q

how are gamma globulin and albumin different

A

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

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10
Q

what is the molecular weight of a typical gamma globulin

A

150,000 daltons

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11
Q

what make up the basic immunologic structure

A

2 identical heavy chains of 50,000

2 light chains of 25,000 daltons

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12
Q

what is papain

A

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

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13
Q

what are fab fragments

A

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

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14
Q

what is an fc fragment

A

crystallizable fragment

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15
Q

what is pepsin

A

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

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16
Q

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

A

it can bind antigen at 2 sites

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17
Q

what is f(ab)2 held together by

A

disulfide bond

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18
Q

what do multiple myeloma tumor cells produce

A

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

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19
Q

patients with multiple myeloma secrete what

A

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

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20
Q

what are immunogloblulin molec held together by

A

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

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21
Q

what are the 2 classes of light chaisn in humans

A

kappa and lambda

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

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22
Q

how many classes of heavy chains are there in humans

A

10

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23
Q

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

A

amino terminal half of the light chain

amino terminal quarter of the heavy chain

24
Q

where are the variable (V) regions located at

A

the end of the chain

-in the amino terminal

25
Q

where are the C regions located at

A

close to the hinge

26
Q

what are the hypervariable regions

A

-highly divergent stretched w/in the V regions

27
Q

what form the antigen-binding cleft

A

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

28
Q

where is the hinged region, what does it do

A

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

29
Q

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

A

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

30
Q

where are complx carbs located on the chains

A

heavy chains in the Fc region

31
Q

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

A

first steps in B cell development

32
Q

what are the major classes of antibody isotypes

A

igG, A, M, E, D

“Gamed”

33
Q

which isotypes can be subdivded into closely related subclasses “subtypes”

A

igA and igG

34
Q

what creates the different isotpes

A

sequence of aa in the heavy chain make the difference

35
Q

which is the first isotype that is released by plasma cells

A

igM

36
Q

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

A

igM

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

37
Q

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

A

igM and igD

38
Q

how do you form secreted igM

A

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

39
Q

which is the first immunoglobulin produced during the immune response

A

igM

40
Q

what is the primary functino of igD

A

rare found in serum

to act as a second antigen receptor

41
Q

what is the major immunoglobulin class found in serum

A

igG

42
Q

what is the role of igG

A

activates complement

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

43
Q

where is igA found

A

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

44
Q

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

A

igA

45
Q

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

A

igA

46
Q

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

A

igA

47
Q

what does the secretory componene tsreve as

A

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

48
Q

what is immune repertoire

A

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

49
Q

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

A
  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
50
Q

what are the antimicrobial functions of secretory igA

A
  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)
51
Q

which isotype are good at complement activation

which is not

A

igG and igM

igA is not good

52
Q

how can antigens enter the body

A
  • from the gut through M cells (delivers antigen directly to underlying immune cells)
  • through more common enterocytes (ep cells taht line the gut)
53
Q

who described monoclonal ab

A

georges kohler

cesar milstein

54
Q

what are hybridomas

A

immortilized cells produced with monoclonal antibodies of pre-determined specificity

55
Q

what are the applications of monoclonal antibody tech

A
  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

OD2-Immunology (4 decks)

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