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cellular basis of immunity > 5 - antibody structure and function > Flashcards

5 - antibody structure and function Flashcards

1
Q

humoral immunity

A

involves soluble substances
mediated by macromolecules in extracellular fluid
e..g secreted antibodies, complement proteins, antimicrobial peptides

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2
Q

antibody defn

A

host protein produced in response to the presence of foreign molecules in the body

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3
Q

antibodies produced by

A

plasma cells

lymphoid lineage

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4
Q

B cell effector cells

A

antibodies

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5
Q

antibody-antigen complex

A

antibodies bind to Fc regions of antigens and opsonise the cells

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6
Q

linus pauling 1940s importance

A

interested in antibody polypeptide structure and its ability to recognise antigens
proposed one immunoprotein that changed its conformation

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7
Q

clonal selection for self tolerance

A

B cells producing antibodies against self antigens are tested and deleted

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8
Q

clonal expansion

A

B cells producing correct specific antibody for the target antigen is activated and multiplied

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9
Q

B cells after infection is over

A

become memory cells and wait in lymphatics

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10
Q

antibodies are

A

glycoproteins

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11
Q

shared functional properties of antibodies

A

all bind to both antigens and immune cells

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12
Q

shared structural properties of antibodies

A

all have Y shaped unit

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13
Q

where do antibodies bind to on an antigen

A

epitope

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14
Q

epitope

A

amino acid sequence on a polypeptide coat protein

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15
Q

paratope

A

antigen-binding region of antibody

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16
Q

where do antigens bind to on an antibody

A

paratope

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17
Q

features of antibody antigen binding

A

reversible
non-covalent

antibodies can change places for a better fit

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18
Q

CDR

A

complementarity determining region

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19
Q

describe structure of an antibody

A

4 polypeptide chains

held together by disulphide bridges and non-covalent bonds

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20
Q

importance of hinge region of antibody

A

enables contortion allowing binding

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21
Q

importance of CDRs

A

hypervariability regions

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22
Q

porter (1959) and Edelman (1961)

A 
worked on structure of IgG
used enzymes to break up antibody  (papain cleavage and pepsin cleavage)
3 fractions (Fab) showed that there were 4 polypeptides
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23
Q

classes of immunoglobulin

A 
IgG
IgM
IgA
IgE
IgD
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24
Q

how are classes of immunoglobulin distinguished

A

by their number of y-units

by their type of heavy chain polypeptide

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25
how many types of light chain polypeptide are there
2
26
no of light chains =
no of heavy chains
27
subclasses of IgG
IgG1 IgG2 IgG3 IgG4
28
valency of 2
2 potential binding sites to target antigen
29
IgM
first response low affinity binding (hypermutation of B cell receptor causes class to switch to IgG) pentameric --> 5 Y units
30
IgG
secondary response principal antibody --> high serum concentration heavy chain = gamma
31
IgA
protects mucous membranes secreted in breast milk and other secretions (tears, mucous, saliva) heavy chain = alpha
32
IgE
protects against parasites and allergies | Fc receptors on mast cells, basophils, eosinophils
33
J chain
holds 5 Y components to make pentameric IgM
34
M cells
relay info to DCs
35
subclasses of IgG
IgG1 IgG2 IgG3 IgG4
36
valency of 2
2 potential binding sites to target antigen
37
IgM
first response low affinity binding (hypermutation of B cell receptor causes class to switch to IgG) pentameric --> 5 Y units
38
IgG
secondary response | principal antibody --> high serum concentration
39
IgA
protects mucous membranes
40
IgE
protects against parasites
41
J chain
holds 5 Y components to make pentameric IgM
42
M cells
relay info to DCs
43
transcytosis
movement of antibody across the epithelium into the lumen side of the gut movement stimulated by docking of antibody to polymeric Ig receptor (with secretory component) on epithelial cell
44
describe release of IgA after transcytosis into gut
protease cleaves the Ig receptor near the membrane IgA - secretory component - polymeric Ig receptor complex
45
role of secretory component
protects and anchors antibody complex at desired location | so phagocytic cell can bin to the Fc receptor and destroy
46
Fc receptor
found on immune cells binds to Fc component of antibodies that are attached to pathogenic cells binding triggers phagocytosis
47
ITAM
immunoreceptor tyrosin-based activation motif important signalling molecule
48
lectin activation pathway of complement
recognition and binding of carbohydrates by collectins e.g. ficolin or mannose-binding lectin is a collecting that binds to mannose on the surface of a pathogen C4 and C2 components are cleaved C2a and C4b bind to form classical C3 convertase on pathogen cell membrane
49
classical activation of complement
triggered by antibody binding to antigen or pentraxins antibody-antigen complex forms series of proteins form C3 convertase cleaves C3 protein C3b binds to C3 convertase to form C5 convertase cleaves C5 protein cleaved products attract phagocytes to site of infection assembly of membrane attack complex conformational change 'fluid-phase' C3 convertase forms cleaves multiple C3 proteins into C3a and C3b
50
CMC
complement mediated cytotoxicity
51
ADCC
antibody attracts to cytotoxic cells via Fc receptors target cell antigens become bound to lots of antibodies effector immune cell lyses target cell
52
Complement mediated cytotoxicity
antibody binding results in fixation of complement onto target cell results in membrane attack complex and cell lysis
53
complement system
formed by soluble/humoral components of serum | 3 activation pathways
54
effects of complement (4)
triggers inflammatory response attracts phagocytes degrades membranes stimulates antibody production
55
3 activation pathways
lectin classical alternative
56
lectin activation pathway of complement
recognition and binding of carbohydrates by collectins e.g. mannose-binding lectin is a collecting that binds to mannose on the surface of a pathogen C4 and C2 components are cleaved they bind to form classical C3 convertase on pathogen cell membrane
57
alternative activation of complement
occurs directly at microbial cell surfaces triggered when C3b protein binds to a microbe ``` conformational change 'fluid-phase' C3 convertase forms cleaves multiple C3 proteins into C3a and C3b C5 convertase forms all pathways follow the same ```
58
ficolin
collectin that binds to N-acetylglucosamine
59
MASP
mannose-binding lectin associates serine protease
60
MAC
membrane attack complex | terminal complement complex that ruptures wall of pathogen
61
3 types of Fc receptor
Fc- gamma Fc-alpha Fc- epsilon

cellular basis of immunity (21 decks)

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