Lecture 4- Antigens and Haptens Flashcards
(106 cards)
1
Q
What is an antigen?
A
Any substance (an organism, a molecule, or part of a molecule) that binds to a B cell receptor, antibody, or T cell receptor
[usually foreign]
2
Q
Antigens have the ability to combine specifically with ______ ______ or sensitized __________
A
antibodies produced ;
T-lymphocytes
3
Q
Where do the antigens originate for exogenous and endogenous?
A
- exogenous - comes from outside
- endogenous - comes from inside
4
Q
What is an immunogen?
A
an antigen that induces an immune response
5
Q
Where are bacterial antigens found?
A
surface of the cell or flagella
6
Q
A small molecule that cannot produce an immune response on its own unless combined with a larger carrier, such as a protein, is called what?
A
hapten
Things “happen everyday but not all things are bad” until combined”
7
Q
Name 3 features of haptens:
A
1) small, low molecular weight substances.
2) not immunogenic by themselves
3) they must use a carrier molecule (protein, albumin, globulins) to elicit a response
8
Q
Give examples of haptans:
A
Simple chemicals and drugs, like
1. penicillin (PCN)
2. sulphonium (ions attached to sulfur)
3. aspirin (ASA)
4. cosmetics
5. tranquillizers
6. neomycin skin ointment
9
Q
What is an epitope (antigenic determinant)?
A
Sites on or within an antigen that antibodies react
10
Q
Antibodies are specific for ______.
unique structures on a B or T cell
A
epitopes
11
Q
The portion of an antigen that is
recognized and bound by an antibody (Ab) or a Tcell receptor (TCR) is called?
A
epitope
12
Q
Another name for epitope is?
A
antigenic determinant
13
Q
How would you describe a multivalent antigen?
A
One type of B cell ;
Many epitopes of the same specificity.
14
Q
How would you describe a polyvalent antigen?
A
Multiple B cells react because it has many epitopes of different specificities.
15
Q
Antibodies only recognize _______ epitopes.
A
native
16
Q
Do pathogens contain multiple antigens?
A
Yes
17
Q
Do antigens contain multiple epitopes?
A
Yes
18
Q
What are the types of antigens?
A
- autoantigens
- transplant
- exogenous
- endogenous
19
Q
What is allograft?
A
tissue that is transplanted from a donor to a recipient who is not an identical twin
20
Q
Which antigens are proteins expressed on the donor tissue that have the capacity to initiate an immune reaction against the allograft?
A
Transplant
21
Q
What are the 2 types of human tissue antigens?
A
Blood group antigens &
Histocompatibility antigens
22
Q
What are the blood group antigens?
A
Type A, Type B, Rh, and O+ antigens
23
Q
What are the 2 histocompatibility antigens?
they are glycoprotein molecules on nucleotide cells that haptens bind to
A
- Major histocompatibility complex antigens (MHC)
- Human leukocyte antigen (HLA)
24
Q
Which class is most potent of the MHC?
A
class I and class 2
25
Describe the Major Histocompatibility Complex Antigens (MHC)
1. A set of cell surface proteins
2. Essential for the adaptive immune system
3. Recognition of foreign molecules
4. Determines histocompatibility (raid rejection of tissue
grafts)
26
MHC presents to which cells?
T-cells
27
The helper T cells recognize foreign antigens on the surface of APCs only when they are presented in the ______ of MHC 2 molecules
groove
28
Cytotoxic T-cells will only recognize antigens, on the surfaces of virus infected cells or tumor cells only when these antigens are presented in the groove of ________ molecules, (MHC _______)
Class I molecule ; restriction
29
How do exogenous antigens enter the body? 2 types are?
Open surfaces: cuts, nose, mouth, surgery, skin, urethra, etc.
bacterial or viral
30
What are the 2 types of bacterial antigen classifications?
those related to bacteria cells and those secreted by bacteria
31
Which antigens are related to bacterial cells?
1. Somatic antigen (O): part of cell wall gm –ve bacter.
2. Capsular antigen (K): usually polysaccharide
3. Flagellar Ag (H) : a protein made of flagellin
4. Fimbrial Ag: surface antigens in fimbriated bacilli
32
What are examples of antigens secreted by bacteria?
exotoxins and enzymes
33
Describe viral antigens AKA viruses:
1. Protein coated viral antigens and
2. Soluble antigens (soluble nucleoproteins as in influenza)
34
What are superantigens (SAgs)?
antigens that activate multiple clones of T-cells, produced by some bacteria and viruses
35
Give example of superantigens (SAgs):
food poisoning, toxic shock syndrome, rheumatic fever, arthritis, Kawasaki syndrome, atopic dermatitis, and guttate psoriasis
36
What are some of the bacterial superantigens?
1. *Staph. aureus*- toxic shock syndrome toxin (TSST), and enterotoxins
2. *Strep. pyogenes* - pyrogenic toxin A
37
Superantigens have the ability to bind to both ______ and _____ .
Class 2 MHC and TCR B chain
38
Superantigens act as a _______ between the MCH class 2 molecules and beta chain, providing a signal for the T-Cell
clamp
39
Superantigens are active at very low concentration causing release of large amounts of _________.
cytokines
40
The massive T-cell activation and release of large amounts of
cytokines cause ________ ________.
systemic toxicity
41
The method of stimulation of superantigens is NOT _______ for the pathogen.
specific
42
Superantigens do not lead to an _______ ______, so there is no memory.
acquired immunity
43
What are substances capable of immunizing the host from which they are obtained?
Autoantigens
44
Self-antigens are ordinarily ___________.
non-antigenic
45
___________ of self-antigens are capable of eliciting an immune response.
Modifications
46
Antigens found within the cytosol of the cell are called?
endogenous antigens
47
Examples of endogenous antigens?
1. viral proteins
2. tumor proteins
3. intracellular bacteria
48
_________ is the ability to induce a humoral (antibody) and/or cell-mediated immune response.
Immunogenicity
49
Immunogenicity can be either _____ or _____ immunogens.
weak or strong
50
What factors influence immunogenicity?
1. How foreign something is
2. Molecular size
3. Chemical structure
4. Route of administration
5. Method of administration
51
Any antigen present only in some of the **same** species that stimulates antibody production in those that lack the antigen is called?
alloantigen (**iso**antigen)
52
Any antigen that occurs in organisms of multiple species is called?
**xeno**antigen
53
allos- is the prefix meaning? (Greek origin)
other
54
xenos- is the prefix meaning? (Greek origin)
stranger
55
What is a xenograft?
a graft of **tissue** taken from donor of one species and grafted into the recipient of another species. Ex: pig heart valves in human hearts
56
T-cells cannot respond to free-floating hapten cells. They must be _____ by the MHC.
processed
57
Which cells are antigen presenting cells?
B-cells, dendritic cells, MOs
58
T-cells recognize antigens from what receptors?
Any receptor, (IgG, IgA)
59
Superantigens do not have to wait for ______ before activating an immunologic response.
a presentation from B-cells or MHC
60
How does molecular size increase or decrease immunogenicity?
High molecular weight increases immunogenicity.
61
How does chemical structure effect immunongenicity?
High complexity increase immunogenicity.
62
Which route of pathogens entering the body has the least effect on immunogenicity?
Oral because stomach acid will kill certain pathogens.
63
What methods of administration effect immongenicity?
antigen dose and adjuvant (immune response enhancer)
(low dose = low zone tolerance
high dose = high zone tolerance)
64
How does the adjuvant increase the immunogenicity?
the substance injected with the antigen can enhance the immunogenicity
65
How does the foreign factor affect immunogenicity?
Tissue from the same species, like allograft, produces a lower immunogenicity than tissue from different species, like xenograft.
66
What are the B-cell receptor (BCR) features?
1. Membrane-bound immunoglobulins (IgM and IgD)
2. Secreted in plasma as antibodies.
67
What are the T-cell receptor (TCR) features?
1. There are alpha and beta chains anchored to the T-cells.
2. There is a groove that binds small peptides presented by MHC on the surface of APCs.
68
What is important about MHC molecules?
They are essential for the presentation of peptides so the T-cell can recognize them and bind to them.
69
What does cross-reactive or heterophile antigens mean?
Heterophile antigens can react with antibodies produced against similar antigens in other species.
70
Usually different species have different antigen sets, but heterophile antigens mean they are ______ between species.
shared
71
The epitopes in cross-reactive or heterophile antigens are ______ or very ______.
identical or very similar
(there is a measure of how related the two antigens are)
72
What immunoglobulin class are heterophile or cross-reactive antibodies?
IgM
73
What example of cross-reactive antigen is given with Vanguard DA2MP?
This vaccine contains canine distemper (CD), **human measles virus**, canine adenovirus -2 (CAV-2) and canine parainfluenza (CPI). The measles virus stimulates cross immunity among 6-wk old puppies regardless of the mom's antibodies that **interfere** with active CD virus immunization.
74
What is Onchocerca cervicalis?
parasite that occurs in horses throughout the world, lives in the nuchal ligament in the neck (cervicalis)
Not zoonotic and affects people with O. volvulus, an invasion of the cornea of the eye, AKA "river blindness" from the eggs of black flies
75
What is moon blindness AKA equine recurrent uveitis (ERU)?
A chronic inflammatory eye disease that affects horses. It is an autoimmune disorder where the body mistakenly attacks the eye tissues.
Treatment aims to reduce inflammation and prevent further damage to the eye. It may include:
1) Corticosteroid eye drops or injections,
2) Immunosuppressant medications
3) Surgery to remove scar tissue or cataracts.
76
If foreign and self-antigens are similar, why is this bad for the host cell? What is this called?
It is called molecular mimicry ;
Not good for host b/c antigens resemble the host cells → host cells are attacked & targeted.
77
An anti-hapten antibody **CAN** bind to _____ hapten or _____ _____ hapten. The molecules are too **SMALL** for TCRs to see without a presenting molecule.
free hapten ; carrier-bound hapten
78
What can recognize specific epitopes whether surface-bound, as free soluble molecules, or degraded fragments?
B cell receptors
79
What receptors can only recognize epitopes when they are bound by MHC molecules?
T cell receptors
80
What is a hapten-carrier conjugate?
a molecule made by attaching a small chemical group (hapten) to a larger molecule (carrier)
81
What does the body produce upon the injection of a hapten carrier conjugate?
anti-hapten antibody and anti-carrier antibody
82
How is antiserum different from antibodies?
antiserum contains different classes of immunoglobulins which may or may not be the target antigen
83
What is auto-coupling?
Haptens spontaneously forming covalent bonds with host cell proteins or polysaccharides. This results in an allergic phenomena.
84
Are all antigens immunogens?
Are all immunogens antigens?
No; yes
85
Adjuvants are considered _______ and are commonly used in __________.
enhancers ; vaccines
86
What blood types are able to receive type A blood?
A and AB
87
What blood types are able to receive type B blood?
B and AB
88
What blood types are able to receive type AB blood?
AB only
89
What blood types are able to receive type O blood?
Everyone
90
Only blood types have the Rh protein?
Positive blood types
91
What recipients cannot receive Rh blood products?
negative
92
Why can't positive blood be donated to negative blood?
Negative blood lacks the Rh factor (protein found on blood cell)
93
Which blood type is the universal donor? universal recipiant?
donor O- ; receive AB+
94
When would the mother's antibodies cross the placenta to attack the baby's blood cells?
On the 2nd pregnancy if she has been exposed to the 1st baby's blood with a postive RH if she has negative RH on delivery.
95
What is a tolerogen?
a substance that causes the immune system to be non-responsive to an antigen.
Example RhoGAM
96
Which type of molecules are most immunogenic?
proteins
97
What is a superantigen?
A protein that activates T cells in a nonspecific and uncontrolled manner
98
What molecular weight is considered immunogenic?
>6000
99
What happens to the antigen presenting cell of a auto-coupled hapten during an immune response?
both the hapten and the presenting cell die
*shoots the messenger*
100
Immunogens contain epitopes that induce a response and is a ______ of the response.
target
101
Why are polyvalent antigens preferred during vaccinations?
It allows many antibody types to potentially bind to that antigen b/c of the higher number of different epitopes on a single antigen.
102
When a MHC antigen is presented to a T-cell what happens to the MHC?
MHC restriction (important for the body to reject transplants)
103
Bacteria can produce an immune response from parts that are related to it. They are?
1. Somatic antigen (O) - outer membrane of cell wall
2. Capsular antigen (K)
3. Flagellar antigen (H)
4. Fimbria antigen (Example K88 and K99 fimbriae is an E. coli that causes diarrhea in livestock, specifically pigs and cattle
104
Theory States: " A particular antigen dictates the formation of the antigen-binding site on B-cells/antibodies"
What theory is this and why is it incorrect?
Theory: Instructional Theory
Incorrect: An antigen-binding site is already formed before the antigen is stimulated.
105
Theory States: "Immune cells are ALREADY specific to a specific antigen
What theory is this and why is it incorrect?
Theory: Selective Theory
Incorrect: As we know, the immune cells [B & T] are DIVERSE and become specific after activation via hypermutations
106
Theory States: "Many clones of a single lymphocytes BEFORE antigen-stimulation"
What theory is this and why is it incorrect?
Theory: Clonal Selection Hypothesis
Incorrect: No, we know that clones are made AFTER antigen-stimulation to enhance specificity
