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IMSE > Week 3 Lec: Antigens and MHC > Flashcards

Week 3 Lec: Antigens and MHC Flashcards

1
Q

The immune response of lymphocytes is triggered by materials called?

A

immunogens

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2
Q

This term refers to a substance that reacts with antibody or sensitized T cells but may not be able to evoke an immune response in the first place.

A

antigen

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3
Q

It is a foreign substance that can initiate an immune reponse.

A

antigen

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4
Q

These are macromolecules that trigger adaptive immune response.

A

antigen

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5
Q

Factors influencing the immune response?

A
  • Age
  • Overall Health
  • Dose
  • Route of Inoculation
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6
Q

Relationship between immunogens and the antigens?

A

All immunogens are antigens but not all antigens are immunogens.

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7
Q

Most common portal of entry?

A

mucous membrane

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8
Q

The ability of an immunogen to stimulate a host response depends on the following characteristics?

A
  • Macromolecular size
  • Chemical composition
  • Molecular complexity
  • The ability to be processed and presented with MHC molecules
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9
Q

Macromolecular size of immunogen?

A

10,000 daltons

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10
Q

Chemical composition of immunogen?

A

composed of protein and polysaccharides; proteins are more immunogenic than polysaccharides

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11
Q

Why do humans accept modifications within their body systems (hip replacement, knee replacement, elbow replacement, artificial heart valve, etc.)?

A

because the materials used for the procedure are made of teflon or nylon, which are non-immunogenic

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12
Q

True or false: pure lipids and pure carbohydrates are never immunogenic.

A

True

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13
Q

How do pure lipids and pure carbohydrates become immunogenic?

A

when they attach and combine with other molecules such as proteins and carbohydrates (ex: lipids + proteins = lipoproteins, nucleic acids + proteins = nucleoproteins, glycogen + lipids = glycolipids)

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14
Q

True or false: Although an immunogen must have a molecular weight of at least 10,000 Dalton, only a small part of the immunogen is actually recognized in the immune response.

A

True

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15
Q

These are molecular shapes or configurations that are recognized by B or T cells.

A

Epitopes

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16
Q

For proteins, epitopes recognized by B cells may consist of ______ amino acids.

A

6 to 15

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17
Q

This key portion of the immunogen is known as the determinant site or?

A

Epitope

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18
Q

Epitope where amino acids follows one another on a single chain.

A

Linear Epitope

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19
Q

Linear Epitope is also called?

A

Sequential

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20
Q

Type of epitope that results from the folding of one chain or multiple chains, bringing certain amino acids from different segments of a linear sequence or sequences into close proximity with each other so they can be recognized together.

A

Conformational Epitope

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21
Q

T-cell epitopes are?

A

linear

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22
Q

They are non-immunogenic materials that, when combined with a carrier, create new antigenic determinants.

A

Haptens

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23
Q

Examples of Haptens?

A
  • Poison Ivy
  • Drug related
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24
Q

Poison ivy (Rhus radicans) contains chemical substances called __________, which are haptens. Once in contact with the skin, these can couple with tissue proteins to form the immunogens that give rise to _______________.

A

catechols; contact dermatitis

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25
Q

Example of drug-related hapten?

A

The best known example of this occurs with penicillin, which can result in a life-threatening allergic response (thrombocytopenia).

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26
Q

Book written by Karl Landsteiner?

A

The Specificity of Serological Reactions

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27
Q

When was the book “The Specificity of Serological Reactions” published?

A

1917

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28
Q

Who was the author of the book “The Specificity of Serological Reactions”?

A

Karl Landsteiner

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29
Q

Karl Landsteiner discovered which concepts?

A
  • Haptens
  • ABO blood group
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30
Q

True or false: Hapten alone cannot stimulate antibody formation.

A

True

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31
Q

True or false: Haptens can still react with antibodies but no complexes form since it is monovalent.

A

True

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32
Q

True or false: When complexed to a carrier, the hapten can stimulate antibody formation.

A

True

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33
Q

If hapten is complexed to a carrier at multiple sites, _________ can take place.

A

agglutination

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34
Q

__________ are those antigens that belong to the host.

A

Autoantigens

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35
Q

True or false: Autoantigens are capable of antibody production.

A

False

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36
Q

__________ are from other members of the host’s species, and these are capable of eliciting an immune response.

A

Alloantigens

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37
Q

They are important to consider in tissue transplantation and in blood transfusions.

A

Alloantigens

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38
Q

Alloantigens are important to consider in?

A

tissue transplantation and in blood transfusions

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39
Q

True or false: Alloantigens are capable of antibody production.

A

True

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40
Q

Tissue transplantation from the host itself. Used for severe/3rd-degree burns (skin from leg/thigh part) and rhinoplasty (skin from earlobe).

A

Autograft

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41
Q

Tissue transplantation wherein the organ or tissues came from a different person. Example: kidney transplant. Tissue match is one criteria before transplantation is approved.

A

Allograft

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42
Q

Tissue transplantation from identical individuals (twins).

A

Isograft/Syngraft

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43
Q

Tissue transplantation from different specie. Example: pig heart to human.

A

Heterograft/Xenograft

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44
Q

Antigens from other species, such as other animals, plants, or microorganisms.

A

Heteroantigens

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45
Q

Those that exist in unrelated plants or animals but which are either identical or closely related in structure so that that antibody to one will cross-react with antigen of the other.

A

Heterophile antigens

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46
Q

Example of Heterophile antigens?

A

Polysaccharide type XIV of pneumococcus reacting with anti-A antisera

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47
Q

It is a substance administered with an immunogen that increases the immune response.

A

Adjuvant

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48
Q

Adjuvant is administered?

A

intramuscularly

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49
Q

Adjuvant acts by producing a ____________ that attracts a large number of immune system cells to the injection site.

A

local inflammatory response

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50
Q

________________ are the only adjuvants approved for clinical use in the United States, and these are used to complex with the immunogen to increase its size and to prevent a rapid escape from the tissues.

A

Aluminum Salts

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51
Q

Another example of adjuvant?

A

Freund’s adjuvant

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52
Q

Freund’s adjuvant consists of?

A
  • Mineral oil
  • Emulsifier
  • Mycobacterium butyricum
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53
Q

Freund’s adjuvant killed?

A

Bordetella pertussis, the causitive agent of whooping caugh

54
Q

Mycobacterium in Freund’s adjuvant accounts for about?

A

0.5 mg/mL

55
Q

True or false: Freund’s adjuvant can be used in humans.

A

False. Freund’s adjuvant cannot be used in humans because it could produce granulomas or large areas of scar tissue.

56
Q

Different Effects of Adjuvants?

A
  • Forms complex to antigen to increase its size
  • Prevent rapid escape from the tissues
  • Increase processing of antigen
  • Stimulate T-cells → that enhance CMI
  • Stimulate B-Cells → enhance HI
  • Also stimulates phagocytic cells
57
Q

Evidence now indicates that the genetic capability to mount an immune response is linked to a group of molecules originally referred to as?

A

Human Leukocyte Antigen

58
Q

The French scientist __________ gave them the name HLA, because they were first defined by discovering an antibody response to circulating white blood cells.

A

Jean Dausset

59
Q

The HLAs are also known as?

A

Major Histocompatibility Complex/MHC

60
Q

Why are HLAs also called MHC?

A

GRAFT REJECTION - because they determine whether transplanted tissue is histocompatible and thus accepted or recognized as foreign and rejected (in short, they place a role in graft rejection)

61
Q

True or false: MHC molecules are actually found on all nucleated cells in the body, and they play a pivotal role in the development of both humoral and cellular immunity.

A

True

62
Q

Gene coding for the MHC molecules in humans are found in the?

A

short arm of chromosome 6

63
Q

All MHC molecules are expressed in all nucleated cells in the body and in?

A

MHC class I

64
Q

Three categories or classes of genes coding for the MHC molecules?

A
  • Class I
  • Class II
  • Class III
65
Q

Class ___ molecules are coded for at three different locations or loci.

A

I

66
Q

Class I molecules are coded for at?

A

three different locations or loci

67
Q

Class I genes are found at three different locations or loci, termed?

A

A, B, and C

68
Q

Class I non-classical genes?

A

HLA - E, F, G

69
Q

Class ___ genes are situated in the D region, and there are several different loci.

A

II

70
Q

Class II genes are situated in the _____, and there are several different loci.

A

D region

71
Q

Class II genes are situated in the D region, and there are several different loci, known as?

A

DR, DQ, and DP

72
Q

Class II non-classical genes?

A

DM, DN, DO

73
Q

Class ___ genes are located in between class I and Class II regions.

A

III

74
Q

Class III genes code for the complement component proteins ________ and cytokine ________.

A
  • C4A
  • C4B
  • C2
  • Factor B
  • tumor necrosis factor (TNF)
75
Q

Class III genes are located in between?

A

Class I and Class II regions

76
Q

Category of MHC molecule involved in antigen recognition?

A

Class I and Class II

77
Q

At each of the loci, or locations of MHC molecules, there is the possibility of?

A

multiple alleles

78
Q

These are alternate forms of a gene that code for slightly different varieties of the same product.

A

Alleles

79
Q

The MHC system is described as __________, because there are so many possible alleles at each location.

A

polymorphic

80
Q

HLA-A has at least _____ different alleles.

A

580

81
Q

HLA-B has at least _____ different alleles.

A

921

82
Q

HLA-C has at least _____ different alleles.

A

312

83
Q

True or false: The probability that any two individuals will express the same MHC molecules is high.

A

False. The probability is very low.

84
Q

There is a possibility of two different alleles for each gene on the chromosome unless that person is __________ (has the same alleles) at a given location.

A

homozygous

85
Q

Means that all alleles that an individual inherits code for products that are expressed on cells.

A

Codominant

86
Q

Contribution from both parental generation.

A

Codominance

87
Q

Because the MHC genes are closely linked, they are inherited together as a package called a?

A

haplotype

88
Q

Thus, each inherited chromosomal region of an MHC molecule consists of a package of genes for?

A

A, B, C, DR, DP, and DQ

89
Q

The full genotype of an MHC molecule would consist of ___________ at a particular locus.

A

two of each gene

90
Q

Class ___ MHC molecules expressed on all nucleated cells.

A

I

91
Q

Highest concentration of Class I MHC molecules are found on?

A

Lymphocytes

92
Q

Class I MHC molecules are low or undetected on?

A

liver hepatocytes, neural cells, muscle cells, and sperm

93
Q

Class I MHC molecules are made up of?

A

Alpha and β2-Microglobulins polypeptide chains

94
Q

Alpha polypeptide chain is folded into three domains?

A

α1, α2, and α3

95
Q

The α chain is folded into three domains is inserted into the cell membrane via a ________________.

A

transmembrane segment that is hydrophobic

96
Q

Alpha polypeptide chain has a molecular weight of?

A

44,000 daltons

97
Q

The α3 region reacts with _____ on cytotoxic T cells.

A

CD8

98
Q

Polypeptide chains that do not penetrate the cell membrane, but it is essential for proper folding of the α chain.

A

β2-Microglobulins

99
Q

β2-Microglobulins has a molecular weight of?

A

12,000

100
Q

True or false: The occurrence of class I MHC molecules is much more restricted than that of class II.

A

False. The occurrence of class II MHC molecules is much more restricted than that of class I.

101
Q

The major class II molecules consist of _______________ that are both encoded by genes in the MHC complex.

A

two noncovalently bound polypeptide chains

102
Q

Most polymorphic MHC class II molecule?

A

DR, which has 18 different alleles

103
Q

The class II has __________ and __________ anchored on the cell membrane.

A

2 alpha chain and 2 beta chain

104
Q

The class II has 2 alpha chain and 2 beta chain anchored on the?

A

cell membrane

105
Q

MHC class II molecule that is expressed at the highest level, as it accounts for about one-half of all the class II molecules on a particular cell.

A

DR

106
Q

The groove where the antigen recognition happens is called?

A

peptide-binding cleft

107
Q

The main role of the class I and class II MHC molecules is to bind peptides within cells and transport them to the plasma membrane, where T cells can recognize them in the phenomenon known as?

A

Antigen Presentation

108
Q

Class I molecules mainly present peptides that have been synthesized within the cell to?

A

CD8+ / T-Cytotoxic cell

109
Q

Class II molecules mainly bind exogenous proteins and present it to?

A

CD4+ / T-helper cell

110
Q

It is thought that the two main classes of MHC molecules have evolved to deal with two types of infectious agents?

A
  • those that attack cells from the outside
  • those that attack from the inside
111
Q

Both MHC class (Class I and II) are synthesized in the?

A

rough ER

112
Q

It keeps the α-chain in a partially folded state while it awaits binding to β2–microglobulin.

A

Calnexin

113
Q

Other term for calnexin?

A

Chaperone

114
Q

Three other chaperone molecules _____, _____, and _____ are associated with the complex and help to stabilize it for peptide binding.

A

calreticulin, tapasin, and ERp57

115
Q

Characteristics of Class I in summary?

A
  • Effective for endogeneous antigens (Tumors, Viruses, Parasites)
  • Presented in CD8+ T-cytotoxic cells
  • Proteasomes/proteosome
  • Transporting peptides (TAP1, TAP2)
116
Q

Function of proteasomes?

A

helps class I for antigen recognition

117
Q

TAP means?

A

transporters associated with antigen processing

118
Q

Characteristics of Class II in summary?

A
  • Effective for exogenous antigens (Bacteria)
  • Presented in CD4+ T-helper cells
  • Invariant chain, Invariant chain peptide (chain that protects the binding site)
119
Q

Digestion of these defective or early proteins is carried out by proteases that reside in large cylindrical cytoplasmic complexes called?

A

proteasomes

120
Q

These are a packet of enzymes that play a major role in antigen presentation.

A

Proteasomes

121
Q

Once cleaved, the peptides must then be pumped into the lumen of the endoplasmic reticulum by specialized transporter proteins called?

A

transporters associated with antigen processing (TAP1 and TAP2)

122
Q

It helps TAP transporters to have close proximity to the newly formed MHC class I molecule and mediates interaction with them so that peptides can be loaded onto the class I molecules.

A

Tapasin

123
Q

Once the alpha-chain has bound the peptide, the MHC I-peptide complex is ______________ to the cell surface.

A

rapidly transported

124
Q

Unlike class I molecules, class II molecules must be transported from the endoplasmic reticulum (ER) to an ______________ before they can bind peptides.

A

endosomal compartment

125
Q

_______________ are the most potent activators of T cells, and they are excellent at capturing and digesting exogenous antigens such as bacteria.

A

Dendritic cells

126
Q

This prevents interaction of the binding site with any endogenous peptides in the endoplasmic reticulum.

A

Invariant chain (Ii)

127
Q

The invariant chain is degraded by a protease, leaving just a small fragment called _____________________ attached to the peptide-binding cleft.

A

class II invariant chain peptide (CLIP)

128
Q

CLIP is then exchanged for __________.

A

exogenous peptides

129
Q

Applications of MHC Typing (HLA typing)?

A
  • Tissue/Organ Transplantation
  • Disease Association
  • Paternity Testing
  • Studies of Racial Ancestry and Migration
  • Forensic Medicine
130
Q

MHC Class II are found in what cells?

A

B cells, APC/Dendritic Cells, Monocytes, Macrophages

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