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IHL Exam 2 > Antigen/Antibody Reactions (Bowden) > Flashcards

Antigen/Antibody Reactions (Bowden) Flashcards

1
Q

Antibody

A

circulating antibodies
-soluble glycoproteins that recognize and bind antigens

-also function as membrane bound surface Antigen receptors on B cells and play a key role in B cell differentiation

they are the effector molecules of humoral immunity

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2
Q

5 classes of Antibodies

A 
IgG
IgM
IgA
IgE
IgD
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3
Q

what makes up the class of an antibody?

A

The heavy chains

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4
Q

Variable regions

A

Fab (fragment antibody)

where antigen binding occurs

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5
Q

Constant regions

A

Fc (fragment constant regions)

biology activity (site of effector function)

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6
Q

CDR’s

A

Complementary-determining regions
aka Idiotope
aka hypervariable region

within variable regions of both H and L chains
(Show exceptional diversity)

Hypervariable regions that are involved in Ag binding by creating an interaction site that is complementary in shape, charge, hydrophobicity to the epitope it binds

6 CDR’s per antibody

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7
Q

Classes also known as …

A

isotype

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8
Q

Allotype

A

Allelic differences in the heavy chains

we all have IgG but we all have subtle differences in the IgG

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9
Q

Idiotype

A

Antigenic determinants on the V regions

we all may see an antigen, but we respond with slightly different V region determinants

see the antigen differently

called Idiotypic Network

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10
Q

Which Ig isotype is NOT bifunctional

A

IgD

usually only on surface of b cells

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11
Q

Antibody functions

A

Binds to antigen and then:
-promotes killing or removal of the immune complex

does this by:

  • binding of the antibody to receptors expressed on host tissues
  • binding of the antibody to the first component of the complement system to initiate the classical pathway
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12
Q

Immune complex

A

Antibody bound to an antigen

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13
Q

IgM

A

Pentamer- expressed on B cells
first antibody produced in primary response to antigen

good for binding Ag’s with multiple repeating epitopes (viruses, RBC’s)
good at binding complement

ha J piece
-binds to secretory cells- provides mucosal immunity

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14
Q

How long does it take for primary response to come up?

A

Two weeks

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15
Q

Why is IgM the first Ab made

A

Because IgM is the first constant region in the gene when looking at the constant regions

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16
Q

sIg

A

Secreted antibody

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17
Q

mIg

A

membrane bound antibody

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18
Q

IgG

A

80 percent of serum

functions:

  • opsonization
  • complement activation
  • antibody dependent cell-mediated cytotoxicity
  • neonatal immunity
  • feedback inhibition of B cells

peaks at birth

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19
Q

4 Subtypes of IgG

A

IgG1
IgG2
IgG3
IgG4

All can cross the placenta

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20
Q

IgG1 and IgG3

A

Bind with high affinity to Fc receptors on phagocytic cells (antibody binds with its C region)

this is opsonization, which leads to increased phagocytosis

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21
Q

IgG2

A

restricted to carbohydrate Ag’s

binds with low affinity

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22
Q

IgG3

A

efficient activator of C’ b/c it has one more complement receptor

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23
Q

IgG4

A

binds with intermediate affinity

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24
Q

CD16

A

CD marker (Fc receptor for IgG)

located on NK cells, monocytes/macrophages and granulocytes

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25
Q

CD32

A 
CD marker (Fc receptor of IgG)
located on B cells (feedback inhibition), monocytes/macrophages and granulocytes
26
Q

CD64

A

Fc Receptor for IgG

located on monocytes and macrophages

27
Q

IgA

A

can have a J piece that binds secretory peptides (produced by epithelial cells)

primary antibody in external secretions (saliva, tears, mucus, bronchial, GU, digestive tracts)

Mucosal immunity***

Primary antibody for the entry point of antigens that you are exposed to through your mucosa

Polymeric-4 binding sites

Very important in baby immunity (breast milk)

28
Q

IgE

A

Low conc. in serum, very short half life

Binds to basophils and tissue mast cells by Fc receptors with very high affinity

Asthma, hay fever, peanut allergies

Helminth infections

29
Q

CD23 a and CD23b

A

Fc receptor for IgE located on mast cells and blood basophils

30
Q

IgD

A

not usually in serum

usually in monomeric form present as an Antigen specific receptor on mature B cells

31
Q

IgM and IgD on surface of B cells have what in common?

A

have same specificity

have the exact same complementary determining regions (CDR’s, aka idiotope, hypervariable region)

32
Q

Antigens

A

foreign molecules that bind to an antibody or TCR ***whether or not they induce an immune response

33
Q

Immunogens

A

Antigens that induce an immune response

34
Q

Epitope

A

part of the Ag that contacts the Ag-binding sites of an Ab or TCR.

this is what binds the idiotope

aka antigenic determinate

35
Q

Pathogen

A

organism that causes disease

36
Q

Haptens

A

small molecular weight molecules that can bind to an antibody but must be attached to a large carrier macromolecule to stimulate an immune response specific for the small molecule

these are used in vaccination
also seen in allergies (penicillin)

37
Q

Endogenous antigens

A

autoantigens- self antigen (autoimmune diseases)

alloantigens–> tissue specific antigen, present in one individual of a species but not in others (ABO)

Intracellular pathogens–> viruses, intracellular bacteria and parasites (chlamydia)

38
Q

Exogenous antigens

A

enter the body or system and freely circulate in the body fluids and are trapped by APC’s

allergens–> immunogen
Microbial
Iatrogenic–> doctor induced

39
Q

Factors influencing immunogenicity (whether something is immunogenic or not)

A

Molecular mass
Foreignness - usually only responds to non self
Chemical composition- more complex, more immunogenic
Physical form- particulate (more immunogenic) vs. soluble, denatured (more immunogenic) vs. native form
Degradability- Ags more easily phagocytosed are more immunogenic
Genetic factors- immunological repertoire
Age- very young and very old
Method of administration (dose, route, adjuvants)

40
Q

Chemical nature of immunogens

A

Proteins- vast majority, good immunogens
Polysaccharides- good immunogens
Nucleic acids- poorly immunogenic, but can be immunogenic when complexed with proteins or single stranded (like viruses)
Lipids-non-immunogenic usually, but may be happens

41
Q

what determines the size of the epitope?

A

The size of the antigen binding site on the Ab

42
Q

Epitopes recognized by B cells

A

B cell interaction with antigens is highly dependent upon the 3-D conformation of the antigen (so don’t have to see things in a linear manner)

epitopes can be associated with both soluble or particulate immunogens

epitopes are usually exposed on the cell surface

43
Q

Epitopes recognized by T cells

A

Only see primary sequence of amino acids in proteins (so not polysaccharides or nucleic acids)

so don’t need epitope on surface, b/c the T cell usually only see size 8-15 amino acid sequence on degraded smaller peptides

DO NOT recognize free peptides or soluble antigens

have to see peptides that are presented to them in bound to MHC (HLA) molecules

44
Q

Epitope properties recognized by B cells

A

Accessible
hydrophilic
mobile peptides containing sequential or nonsequential amino acids

45
Q

Epitope properties recognized by T cells

A

Internal linear peptides produced by processing of antigen and bound to MHC molecules

46
Q

T dependent antigens

A

An Ag that requires both Th cells and B cells to stimulate an Ab response

always proteins***

required for class switching of antibodies and affinity maturation

47
Q

T independent antigens

A

Non protein Ag’s (polysaccharides or lipids)

stimulate antibody response without T help

Usually identical epitopes that can cross-link BCR

48
Q

Mitogens

A

Substances that cause cells (lymphocytes) to undergo cell division

49
Q

LPS

A

a mitogen

activator of human B cells (does not need t cell help)

50
Q

Superantigens

A

Antigens that activate a large fraction of the T cells

these are not processed but bind directly to MHC class II molecules and Vbeta of the TCR

diseases that happen from these are in part due to hyper-activation of the immune system and subsequent release of biologically active cytokines by activated T cells

51
Q

Ab/Ag Binding

A

form non-covalent bonds (H bonds, electrostatic, Van der waals, hypdrophobic)

reversible interaction

52
Q

Affinity

A

the strength with which one Ag-binding surface of an antibody (idiotope) binds to one epitope of an antigen

53
Q

Avidity

A

Each antibody molecule can bind 2 to 10 epitopes of an antigen (depending if its IgA, IgM… etc.) or epitopes on two or more neighboring antigens.

The total strength of binding is much greater than the affinity of a single antigen-antibody bond

54
Q

The avidity of an Ab for its Ag is dependent on…

A

the affinities of the individual Ag combing sites

55
Q

how are hapten/carrier complexes used in drugs…

A

drugs alone are poor stimulators of immune responses due to simple/small structure

so…. these drugs form hapten-carrier complexes by binding a protein that is not immunogenic in free form

basis for many drug allergies

56
Q

Monoclonal antibodies

A

antibodies derived from a single B cell clone

using this means that monoclonal antibodies against virtually any antigen can be produced

57
Q

how do you make monoclonal antibodies

A

isolate spleen cells from mouse immunized with antigen X (Some of these are producing anti-X Ab)

fuse spleen cells with immortal myeloma cell line

Culture in medium

only fused cells (hybridomas grow)

select hybridomas that are producing monoclonal anti-X antibody

58
Q

First drug for melanoma

A

Yervoy (Ipilimumab)

this is a monoclonal antibody that downregulates the immune response ???

59
Q

ELISA

A

coat wells with antigen of interest

fill well with pt’s fluid of interest

if the pt’s fluid of interest contains antibodies against specific antigen it will bind

the wells are then washed…
next second antibody is added specifc for first antibody
also the second antibody has enzyme on it…

next wash again to remove all unbound second antibody

so next add substrate and if there is a color change then you know antibodies are present

60
Q

Flow Cytometry

A

?

61
Q

Recombinant antibodies

A

commonly used as therapeutic reagents in cancer immunotherapy

IHL Exam 2 (14 decks)

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