Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

YEAR 2 S2 IMMUNO > Theme 3 - 3a (antigens and antigen receptors) > Flashcards

Theme 3 - 3a (antigens and antigen receptors) Flashcards

1
Q

what is an immunogen

A

an antigen that promotes an immune repsonse in the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

are all immunogens antigens

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

are all antigens immunogens

A

no eg self antigens don’t promote a response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is an antigen

A

any molecule that can bind to an antigen receptor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are the 2 types of antigen receptor

A

on surface of B cell
or
on surface of T cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is the B cell antigen receptor called

A

IMMUNOGLOBULIN
either in the form of B cell receptor complex (on surface of B cell) or when they are SECRETED from the B cell (when the B cell become PLASMA CELLS) they are called ANTIBODIES

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what allows the immune system to respond rapidly to its SECOND encounter with a pathogen

A

its memory

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what triggers specific immune responses

A

antigens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

which cells are part of specific immunity

A
  • APCs (antigen presenting cells)

- B and T lymphocytes w/ specific Ag receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are the main APCs

A
  • monocytes
  • dendritic cells
  • macrophages
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are the phases of an adaptiive immune response

A

1) RECOGNITION phase
2) ACTIVATION phase (antibody producing cell, effector T cells)
3) EFFECTOR phase (elimination of pathogen)
4) DECLINE (homeostasis)
5) MEMORY (surviving memory cells)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

where does most antigen recognition occur?

A

in secondary lymphoid tissues (eg lymph node)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

different antigens are detected how/where

A

they are detected in different secondary lymphoid tissues

  • eg lymph node detects antigents from within tissue
  • spleen detects antigens from blood
  • mucosal tissues have other methods
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is an antigen

A

Ag is any substance that binds to specific receptors on lymphocytes ie B cell receptor (BCR) or T cell receptor (TCR)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is an antigenic determinant/epitope

A

the part of the Ag that binds receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is an immunogen

A

any molecule or group of molecules that induce an immune response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

describe the relatioship between immunogens and antigens

A

ALL immunogens are antigens, NOT all antigens are immunogens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is a hapten

A

a small molecule that can ACT as an epitope but NOT elicit an immune response on their own, they have to be BOUND to something else to elicit an immune response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

an antigen can be what

A
  • a protein/lipid/carbohydrate or a combination of these
  • may be FOREIGN or ALTERED SELF molecule
  • may be SOLUBLE or PARTICULATE, SIMPLE or COMPLEX with many different antigenic determinants each of which comprises a small number of AMINO ACIDS, CARBOHYDRATES or LIPID RESIDUES
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

antigens are most commonly what

give examples

A

proteins or large polysaccharides from foreign organisms: eg components of bacterial cell walls, capsules, pili, flagella, proteins of viruses, fungi and protozoa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

non micorbe derived antigens can be what

A
  • pollen
  • food
  • dust
  • ‘self’ antigens from dead/senescent cells or altered self molecules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

how can antigens enter the body

A
  • breaks in skin and mucous membranes
  • direct injection (bite/needle)
  • organ transplants/skin grafts
  • M cells in the mucosal surfaces
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

give examples of simple antigens

A
  • benzene
  • ovalbumin (from eggs)
  • pollen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

give examples of complex antigens

what do they invoke

A
  • Corona virus
  • bacteria

these can have multiple epitopes, they invoke a POLYCLONAL immune response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

give example of an exogenous antigen

A
  • bacteria
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

are viruses endogenous or exogenous antigens?

A

viruses aren’t ‘living’ until they are inside a host cell and can replicate

  • the proteins that they express can end up on the SURFACE of the infected cell
  • but since the cells are from the organism itself it is an ENDOGENOUS antigen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what type of antigen is a self antigen that cuases disease

A

an auto antigen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

all antigens are not equally immunogenic, tru or false

A

true

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what characteristics of an antigen give it HIGHER IMMUNOGENICITY

A
  • larger
  • INTERMEDIATE dose (high/low dose can cause lower immune response)
  • entrance via SUBCUTANEOUS (skin)
  • complex antigens
  • in a PARTICULATE form and DENATURED
  • have MULTIPLE differences to a self protein
  • slow release ADJUVANTS, BACTERIA
  • EFFECTIVE interaction with host MHC
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

how can we INCREASE the immunogenicity of an antigen used in vaccine

A

use of ADJUVANTS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what does an adjuvant do

what are they freq used in

A

enhance the immune response to an antigen, making it MORE immunogenic
- freq used in vaccines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what do adjuvants inc

A
  • persistence ‘depot’ (the antigen is present for longer before being cleared by liver)
  • effective size (for uptake by APCs)
  • activation of DENDRITIC CELLS, MACROPHAGES–> inflammatory cytokine production
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

what are examples of adjuvants

A
  • COMPLETE FREUND’S ADJUVANT (oil, water, dead:lysed mycobacteria)
  • alum (aluminium potassium sulphate)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

which receptors are part of the adaptive (specific) immune system

A

BCR- B cell receptor (immunoglobulin/antibody)

TCR- T cell receptor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

which receptors are part of the innate (non specific) immune system

A

Pattern Recognition Receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

which receptors are IN BETWEEN the innate and ADAPATIVE immune systems?

A

NK cells killer activatory immunoreceptors

KARs such as NKG2D

37
Q

what do B cell receptors bind

A
  • bind ‘native’ antigen in solution/suspension

- recognise the 3D conformation of the antigen via BCR (surface immunoglobulin or sIg)

38
Q

what is BCR sometimes called

A

surface immunoglobulin (sIg)

39
Q

what do T cell receptors bind

A
  • binds linear arrays of approx 9 aa via TCR

- antigen has to be processed and presented on an Ag presenting cell using MHC

40
Q

what is the structure of antigen receptors

A
  • includes IMMUNOGLOBULIN folds
  • this consists of ANTI-PARALLEL BETA PLEATED SHEETS held together by disulphide bonds
  • highly variable LOOPS on either side of B pleated sheet which give rise to functions
41
Q

where are immunoglobulin folds found?

A

antigen receptors, adhesion molecules, MHC molecules

42
Q

what are immunoglobulins

A

proteins that recognise and bind to a particular antigen with VERY HIGH SPECIFICITY

43
Q

what are the 2 forms of immunoglobulins:

the structure of the Ig or antibody molecule allows it to ?both recognise and bind

A

1) bound to the surface of B cells —> BCR
2) made in response to exposure to the antigen —> ANTIBODIES

  • both molecules have the same structure but are either bound to the membrane or secreted by fully activated B cells (plasma cells)
  • the structure of the Ig or antibody molecule allows it to both recognise and bind to antigen as well as carry out different effector mechanisms
44
Q

what are the differences between BCR and antibody

A
  • BCR has short SPACER segment which anchors it to the B cell
  • BCR is in the TRANSMEMBRANE DOMAIN

other than this they are identical

45
Q

the BCR and antibody made by one cell will do what

A

will recognise and BIND to ONE particular antigen with V HIGH SPECIFICITY
- will also be of the SAME CLASS of immunoglobulin (the constant regions of the antibodies will be same)

46
Q

what are the names of the parts of immunoglobulin structure

A

1) MONOMER
2) AMINO TERMINAL seq of variability ) - Fab (frag Ag Binding)
3) REST OF MOLECULE (CONSTANT) -Fc

47
Q

describe each part of immunoglobulin structure

A

1) MONOMER: flexible Y shaped molecule w/ 4 protein chains (2 identical light chains and 2 identical heavy chains)
2) AMINO TERMINAL has seq of VARIABILITY (V) has V heavy (VH) and VL (V light) which form ANTIGEN BINDING SITE - ‘Fab’ (fragment of antigen binding)
3) CONSTANT structure - Fc
- can be CL (constant light) which can be κ or λ chains
- or CH (constant heavy) which can be CH1, CH2, CH3, CH4 and stabilised by intrachain disulfide bonds
- Can be μ, γ, α, δ, or ε chains depending on the class

48
Q

what happens in the variable region of immunoglobulin

A

it is the antigen binding site

49
Q

what is the structure of the antigen binding site

A
  • made up of Ig folds that contain 3 hypervariable loops between the strands of the β-pleated sheets
  • called CDRs (complementarity-determining regions), which vary in length and amino acid composition
  • this variability is what gives the immune system diversity, because each BCR is different
50
Q

in which region of an immunoglobulin are effector functions ususally found

A

constant regions

- these are mediated through binding to cellular Fc receptors and complement activation

51
Q

what are the 5 classes of immunoglobulins

A
  • IgM: found on surface of naïve B cells
  • IgA, IgE and IgG – Found on the surface of B cells that have been activated and have undergone “class-switching”
  • IgD – Found on all B cells (function unknown)
52
Q

what determines the 5 classes of immunoglobulins

A

the genome of the B cell

O the BCR and the ANTIBODY made by a certain B cell clone will be the SAME

53
Q

different antibody types are induced by what

A

different types of antigen, the entry route of the antibody function needed to mould the immune response to the type of invader encountered

54
Q

IgM has what shape

A

pentamer (5 copies of antibody join together)

55
Q 
IgA is found where
what is the class specific structural features of IgA
A

mucosal secretions

  • it is a dimer, joined by the J chain and secretory component
56
Q

what is the function of IgA

A

agglutination and neutralisation

57
Q

what is the function of IgD

A

unknown

58
Q

what is the function of IgE

A

triggers histamine release from basophils and mast cells

59
Q

what is the function of IgG

A

Complement activation, agglutination, opsonization and neutralisation, crosses placenta to protect foetus

60
Q

what is the function of IgM

A

Complement activation, agglutination and neutralisation

61
Q

what does each B lymphocyte have in terms of immunoglobulin copies

A

has multiple copies of an immunoglobulin with single antigen specificity

  • due to the ‘randomly’ generated antibody variable regions that occur genetically during B cell development
  • but the BCRs on all an individuals B cells COMBINED can recognise millions of different antigenic determinants
62
Q

since immunoglobulins dont have signalling molecules to signal to B cell that they have bound antigen what do they do

A
  • using 2 Igα and 2 Igβ (CD79a and CD79b) and memb bound Ig (mIg)
  • they have long cytoplasmic chains that have Immunoreceptor Tyrosine kinase Activatory Motif: ITAM
  • when antigen binds variable region, you can get clustering of receptors which causes activation of ITAM
63
Q

what happens once the ITAMs of Igα and Igβ transmit the signal if the mIgM binds antigen?

A

leads to development of either plasma or memory cells

  • once developed into plasma cells they probably DONT express BCR on surface, instead they secret ANTIBODIES (same variable regions and Ig subclass as surface BCR)
  • memory B cells cont to express BCR (but as IgG, IgA or IgE)
64
Q

where do B cells develop from

A

progenitors in bone marrow

65
Q

describe the process of B cell expression of BCR

A

genes coding heavy and light chains are rearranged giving each cell a unique BCR to recognise an epitope

  • the resulting cells which cannot make functional heavy or light chains die by apoptosis (positive selection), as do those which bind to self molecules whilst arranging their BCRs (negative selection)
66
Q

immunoglobulin genes contain which segments

A

segments known as VDJ segments:

  • V = Variable Segments
  • D = Diversity Segments
  • J = Joining Segments
67
Q

heavy and light chains cont which segments each

A

BOTH cont V and J

HEAVY chain cont D segments

68
Q

how is diversity achieved

A

there are many copies of each of these segments, one of these is selected each

69
Q

antibodies recognise which part of an antigen

A

epitopes: the parts of antigen that contact the antigen binding sites of an antibody or T cell receptor

70
Q

what must be the case for the antibody to fit

A

the molecular ‘shape’ of the epitope and the variable regions must ‘fit’

71
Q

epitopes can be what

A

linear or discontinuous

72
Q

what is each antigen binding site made up of

A

the Complementarity Determining Regions (CDRs) of two different Immunoglobulin folds

  • These are at the furthest extreme of the heavy (VH) and light chains (VL)
  • These are so close together in the 3D structure of the antibody that they make one continuous paratope
73
Q

what determines how tightly the epitope and paratope bind?

A

their complementarity

  • the higher the complementarity the stronger the binding. The strength of the reaction is referred to as the affinity of the antibody
  • generally: a high affinity antibody is more protective against pathogen than a low affinity antibody because it will bind antigens at lower concentrations
74
Q

what is the antibody avidity

A

the total strength of binding of the Fab regions of the population of antibodies raised against an antigen, and involves the reaction with all antigenic determinants

75
Q

which class of immunoglobulin has low affinity

A

IgM

76
Q

describe affinity

A

ONE antigen binding site

ONE epitope

77
Q

describe avidity

A

MULTIPLE antigen binding sites

REPEATED epitopes

78
Q

IgM has high what and low what ?

A

LOW affinity
HIGH avidity: the 10 variable (Fab) regions, the have high avidity, and are still very effective against whole pathogens and are very effective activators of complement

79
Q

what are the 2 main components of BCR

A

1) memb bound Ig

2) signalling chains CD79 alpha and beta

80
Q

where are the parts of heavy chain of the memb bound Ig

A
  • a short cytoplasmic domain
  • a transmembrane region
  • the rest of it is EXTRACELLULAR
81
Q

what is the extracellular domain of the membrane bound HEAVY chains Ig on BCR composed of

A
  • 4/5 Ig like domains
    3/4 of these are CONSTANT regions
    1 is a VARIABLE region
82
Q

how are the two chains of the extracellular domain of memb bound Ig joined

A

disulphide bond in the HINGE region

83
Q

what is the structure of the light chains on the extracellular domains of the memb bound Ig on BCR

A

two light chains are ATTACHED to the heavy chain (they dont go through the membrane)
- form TWO Ig like domains

84
Q

on the memb bound Ig, where does the antigen bind

A

the TWO VARIABLE regions of the chains come together to form the antigen binding site

85
Q

how many antigen epitopes can one memb bound Ig bind

A

TWO as there are TWO sets of variable regions

86
Q

what does the memb bound Ig have to associate with to communicate to B cell that it has bound antigen?

A

CD79 alpha and beta

87
Q

what is the structure of CD79 alpha and beta

A
  • a small EXTRACELLULAR portion that has a Ig domain externally
  • a transmembrane region
  • a LONG CYTOPLASMIC tail that is able to SIGNAL (which have IMMUNORECEPTOR TYROSINE ACTIVATORY MOTIFS - ITAMS)
88
Q

what does ITAM stand for

A

IMMUNORECEPTOR TYROSINE ACTIVATORY MOTIFS

89
Q

what are the CD79 alpha chains joined by

A

BETA chains, which CO ASSOCIATE with MEMBRANE BOUND Ig to form BCR
- CD79 also has ITAMs

YEAR 2 S2 IMMUNO (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions