Immunology Test 1

Front 1

Adaptive Immune Response

Back 1

characterized by the recognition of foreign antigen and including both the humoral and cell-mediated response

Front 2

Two molecules are involved in the Adaptive Immune Response:

Back 2

1. immunoglobulins - humoral response

2. TCRs - cell-mediated response

Front 3

Immunoglobulins

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a group of glycoproteins present in the serum and tissue fluids of all mammals.

Front 4

Some immunoglobulins are carried on the surface of B cells where they act as ____.

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receptors

Front 5

An immunoglobulin is considered an antibody when...

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it is free in the blood and/or lymph

Front 6

Five distinct class of immunoglobulins

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IgG, IgA, IgM, IgD, IgE

Front 7

Immunoglobulins are bi-functional molecules. Name the two important areas on an Ig that are important.

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1. Fc portion
2. Fab portion

Front 8

Fc portion of an Ig

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binds to receptor on macrophage or to complement porteins; known as effector function - able to effect cells

Front 9

Fab portion of Ig

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antigen binding domain - binds to antigen

Front 10

Immunoglobulin class and subclass depends on ________.

Back 10

structure of the heavy chain

Front 11

The basic structure of all immunoglobulins is a unit consisting of _______ and _______.

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- light chain polypeptide chains
- heavy chain polypeptide chains

Front 12

variable region of immunoglobulin

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-top portion of light and heavy chain
-has a lot of variation
-needs to be different in order to recognize thousands of antigens
-accounts for variability

Front 13

hinge region of immunoglobulin

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-allows flexibility, which is necessary in order to extend outward to bind antigen

Front 14

2 heavy chains are linked by _____ bonds at the _____ region.

Back 14

disulfide, hinge

Front 15

The immunoglobulins differ in which chain?

Back 15

constant heavy chain

Front 16

Allotypic variation

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refers to genetic variation (different alleles at a given locus) between individuals within a species

Front 17

Idiotypic Variation

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variation in the variable domain produces idiotypes. Idiotypes determine the binding specificity of the antigen binding site

Front 18

Immunoglobulin subclasses

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there are subclasses of Ig that have slight differences in their heavy chains. they are named with a greek letter.

Front 19

IgG subclasses

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IgG1, IgG2, IgG3, IgG4 and their heavy chains are called gamma 1, gamma 2, gamma 3, gamma 4

Front 20

IgA subclasses

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IgA1 and IgA2 and their heavy chains are alpha 1 and alpha 2

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IgM, IgD, IgE subclasses

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there are no subclasses for these immunoglobulins

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Function of IgG

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-major Ig in normal human serum
-consists of a single four-chain molecule
-the early antibody: 1st Ig class produced in primary response to antigen because it has 10 potential binding sites (for 10 different pathogens)

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Function of IgD

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-less than 1% of total plasma Ig, but it is present in large quantities on the membrane of many B cells

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kappa and lambda

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Constant light chains exist in two distinct forms. These are isotypes.

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IgA

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-found in external secretions, such as breast milk, saliva, tears, mucosal surfaces
-has 2 subclasses: IgA1, IgA2

Front 26

Function of IgE

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-scarce in serum, found on surface membrane of basophils and mast cells
-has very short half life until it binds to the Fc receptor on surface of mast cells
-plays role in immunity against parasitic helminths
-associated with allergic diseases such as asthma and hay fever

Front 27

B cells can have more than one ______ expressed on its surface, both recognize the same antigen, but will only have one ______, ie. are only specific for one antigen.

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isotype, idiotype

Front 28

Isotypic Variation

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the genes for isotypic variants are present in all healthy members of a species,gamma1,gamma2,gamma3,mu,alpha1,alpha2,delta,epsilon,kappa,lambda are all present in the human genome and therefore they are isotypes
-isotypic determinants are constant region determinants that distinguis each Ig class & subclass w/in a species

Front 29

The enzyme ______ cleaves the IgG molecule in the hinge region between Cgamma1 & Cgamma2 to yield 2 identical Fab regions & 1 Fc fragment.

Back 29

papain

Front 30

The enzyme _______ generates two major fragments of IgG: the Fab’2, which includes the 2 Fabs + hinge region & the pFc' fragment that corresponds to the Cgamma3 domain

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pepsin

Front 31

a reason to digest antibodies:

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small antibody fragments are used to attach chemicals and target tumor cells (the entire antibody is too large).

Front 32

Within the variable region of the heavy & light chains are short polypeptide segments that show exceptional variability and are termed _____.

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hypervariable regions

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Hypervariable regions are located where on the variable regions of the heavy and light chains?

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amino acids 30,50,95

Front 34

Hypervariable regions are referred to as ______, which means _____.

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CDRs, which means complementarity determining regions

Front 35

when amino acids fold, the region at amino acid 30, 50, 95 in both heavy and light chain are the regions that _______________.

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the regions that reach out for the antigen.

Front 36

Framework regions (FRs)

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the intervening peptide segments situated between CDRs (hypervariable regions) within the variable regions of heavy and light chains.

Front 37

In both heavy and light chains, there are ____ CDRs and _____ FRs. (numbers)

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3,4

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TCR-1

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-called gamma/delta has a gamma and a delta chain
-present in low amounts (5-10%)

Front 39

TCR-2

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-heterodimeric molecule - made up of two different pp chains
-alpha and beta chain linked by disulfide bond
-90-95%

Front 40

Both forms of TCR (αβ and γδ) associate with a number of polypeptides which are collectively called _____.

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CD3

Front 41

CD3 association with the TCR is necessary for ______.

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surface expression of the TCR complex at the cell surface

Front 42

T/F: CD3 is a part of the TCR receptor

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False: CD3 is NOT a part of the TCR receptor but it is necesarry for surface expression of TCR complex.

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T/F: CD3 aids in generating diversity associated with TCRs.

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False: CD3 has no amino acid variability on different T cells, thus cannot generate diversity.

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T/F: CD3 is required for signal transduction

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True

Front 45

_____ comprises at least 5 invariant polypeptides called γ,δ,ε,ζ,η.

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CD3

Front 46

T/F: CD3 is not necessary for T cell activation

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False: CD3 is necessary for T cell activation

Front 47

Important feature of the transmembrane domain:

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it contains a negatively charged amino acid rather than being apolar

Front 48

the cytoplasmic domain of each CD3 contains a sequence motif called _____ that is important for signal transduction.

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ITAM (immunoreceptor tyrosine-based activation motif)

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What does ITAM do?

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interacts with protein tyrosine kinase, which phosphorylates tyrosines on the ITAM sequence and sends signal to the nucleus that tells the promotors of IL-2 and IL-2 receptor genes to start being expressed

Front 50

What happens in response to IL-2?

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-T helper cell proliferation
-B cell proliferation

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When is CD3 phosphorylated?

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T cell receptor must first bind to peptide and then engage CD3 before phosphorylation of CD3 occurs.

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Class ____ MHC is referred to as an open structure because it can bind 13-18 peptides.

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MHC II

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Several hundred different allelic variants of Class I and II MHC molecules have been identified. However, one individual only expresses a small number of these molecues. List the number of possibilities for MHC I and MHC II.

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MHC I - up to 6
MHC II - up to 12

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promiscuous binding

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MHC molecules do not exhibit fine specificity of antigen binding of antibodies or TCRs. Instead, a given MHC molecule can bind to numerous peptides and a give peptide can bind to numerous MHC molecules.

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Class ____ MHC has a peptide binding cleft that is blocked at both ends. What is the result of this?

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-Class I MHC
-as a result, it can bind peptides that contain 8-10 amino acid residues.

Front 56

Class ____ MHC has a peptide binding cleft that is open at both ends. What is the result of this?

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-Class II MHC
-as a result, it can accomodate larger peptides of 13-18 amino acid residues.

Front 57

Class I MHC molecues bind peptides and present to ______ T cells.

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CD8+ T cells

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Class II MHC molecules bind peptides and present to ______ T cells.

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CD4+ T cells

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anchor residues

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amino acids found on class I MHC molecules that anchor the peptide into the groove and give the MHC I molecule the ability to bind to a diverse spectrum of peptides.

Front 60

Locomotion of prokaryotes

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1. Flagella
2. Axial filament

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Axial filament

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-internal flagella
-found in periplasm
-not extending out of cell wall
-move in wiggling motion
-typical of spirochetes
ex. Treponema pallidum
Syphilis

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Attachment of Prokaryotes

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1. Pili
2. Fimbria
-N.gonorrhea
-mutans lacking fimbria
are not pathogenic

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Glycocalyx

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-capsule and slime layers
-loose polysaccharide or protein layers surrounding some bacteria
-aid in resistance to phagocytosis
-capsules are tight and slime layers are loose

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Peptidoglycan layers

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-chains of NAM and NAG

Front 65

What blocks the cross linkages of the peptidoglycan layer?

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Penicillin

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Cell wall of Gram + organisms

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-stain purple
-very thick peptidoglycan layer
-techoic acids embedded in peptidoglycan

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Cell wall of Gram - organisms

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-stain pink
-more complex cell wall
-very thin peptidoglycan layer
-outer membrane external to peptidoglycan
-LPS (lipopolysaccharide)

Front 68

T/F: both Gram + and Gram - cells produce endotoxins

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False: Gram - cells produce endotoxins.

Front 69

Cell wall of Genus Mycobacterium

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-stains gram +
-mycolic acids, waxy polysaccharides, embedded within peptidoglycan layer make these organisms more resistant to drying & other environmental factors

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Cell wall of genus Mycoplasma

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-lack peptidoglycan cell wall all together

Front 71

Site of aerobic respiration in bacteria

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-cytoplasmic membrane
-because bacteria lack mitochondria

Front 72

Diversity amongst bacterial populations occurs how?

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1. Mutations
2. Recombinations
-transformation
-transduction
-conjugation
-transposition

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Transformation

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-donor DNA from dead bacterial cell becomes fragmented
-DNA leaves cell when cell dies/bursts
-other cells can pick up free DNA if they are competent
-foreign DNA recombines with host cell DNA
-must occur during active phase of cell growth

Front 74

competent

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ability of cell to pick up foreign DNA

Front 75

Transduction

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-virus(bacteriophage) carrying viral DNA
-infects cell & causes cell's DNA to fragment
-sometimes the phage capsid assembles w/bacterial DNA instead of phage DNA
-therefore, if phage infects new cell, it does not kill it
-new DNA will find homologous area on bacteria chromosome & crossing over occurs
-replaces segment of bacterial chromosome

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Conjugation

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-F plasmid (Fertility plasmid) which possesses genes for pilus formation
-pilus is produced & attaches to F- bacterial cell
-through rolling circle replication, a piece of F plasmid & some of bacterial gene is tranferred
-this recombines with second bacterial chromosome
-Hfr(high frequency of recombination) cell

Front 77

Transposition

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-segments of DNA(aka jumping genes) can move around & are transposable elements
-transposable element is replaced & inserted into plasmid (or vice versa)
-some TE are not replicated but are lost at original location & move around
-believed that Resistance to antibiotics is because of Transposition
-really no way to stop it because it is random

Front 78

Endospore formation

Back 78

-helps to surpass adverse conditions
-Genera Bacillus & Clostridium
-in the face of adverse conditions, organisms cease metabolically active state(vegetation) to a dormant state(sporulation)
-endospores are formed
-dehydration w/in spore is believed to be reason that these cells can survive
-increased calcium & dipicolinic(?) acid causes dehydration
-normally boiling cells causes water w/in cell to release steam & cause denaturing
-by removing water, this can't happen

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Eukaryotic Structure

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-flagella-move in whip-like motion & are made of microtubules
-Cilia
-Glycocalyx
-Cell wall-not all have cell wall
-cell membrane
-organelles

Front 80

How do eukaryotic flagella differ from prokaryotic flagella?

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-eukaryotic: move in whip-like motion
-prokaryotic: move in 360 degree motion

Front 81

Eukaryotic Organelles

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-nucleus:contains the DNA which is carried on chromosomes
-nucleolus:site of RNA synthesis
-rough ER:site of protein synthesis
-smooth ER: site of protein
modification
-Golgi:protein sorting & glycosylation of protein
-mitochondria
-lysosomes

Front 82

Do all eukaryotes have a cell wall?

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Not all eukaryotes have a cell wall.
-protozoa lack cell wall
-molds, yeasts, algae have cell wall but it is not made up of peptidoglycan

Front 83

Types of Eukaryotes

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-Fungi: molds & yeasts
-Protista: protozoa, algae, slime molds
-Animalia - microscopic worms (helminths)
-Plantae

Front 84

Molds

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-multicellular = one cell/cross wall/another cell
-cross wall = septate
-no cross wall = aseptate
-vegetative hyphae
-reproductive hyphae: spores are formed & used for reproduction
-mycelium = a colony of mold that is visible to the eye

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Mycelium

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a colony of mold that is visible to the eye

Front 86

Yeast

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-unicellular
-ovoid structure
-reproduce through budding
-pathogenic upon inhalation
-enter body either directly through skin contact or inhalation

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Protozoa

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-single celled
-appear like animal cells because lack cell wall
-pathogenic protozoa typically appear in tropical locations
-ingestion in form of cyst
-can be intra or extracellular

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trophozoite

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actively feeding protozoa

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cyst

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-dormant form of protozoa
-can contaminate water sources
-ingested & switch to actively growing form
-amoebic disentary

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Animalia

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-Helminths
-either microscopic or visible to the eye
-enter body either through ingestion (larvae found in meat or pinworm eggs found in soil) or active penetration (muddy water; will break skin and travel up leg) and arthropod bites

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Viruses

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-not cells
-particles: phage or viral particles
-can be very small of large
-composed of protein capsid embedded w/nucleic acid either RNA or DNA but not both
-naked or enveloped

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__________ are the subunits of a capsid

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capsomeres

Front 93

T/F: A viral capsid is made of both RNA and DNA

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False: a viral capsid is made of either RNA or DNA but not both

Front 94

Types of capsids

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1. helical - ex. TMV
2. icosahedral: 20 equilateral triangles forming 12 vertices; most efficient way to hold nucleic acid
3. complex: are neither helical or icosahedral - ex. bacteriophage

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bacteriophage

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viruses that infect bacteria

Front 96

Virus: naked vs. enveloped

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1. naked
-nothing covering capsid
-naked cells survive longer than enveloped
2. enveloped
-virus obtains from host cell a cytoplasmic membrane
-do not lyse host cell but instead exit through a budding process during which they obtain the membrane

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Types of Viral Infections

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1. Lytic
2. Persistent - always making virus
3. Latent - do not produce viral particles rather latent RNA is present (LAT RNA) and reactivation event causes production of virus
4. Transformation of normal cells into tumor cells

Front 98

What type of cell are bacteria?

Back 98

-prokaryotes

Front 99

Explain the DNA of bacteria

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-have a long ds circular molecule of DNA
-the DNA is tightly coiled in a region called the nucleoid; may also contain extrachromosomal DNA called plasmids
-plasmids may encode toxins and other enzymes that increase the virulence of the
microorganism

Front 100

T/F: Bacteria have ribosomes but lack any membrane bound organelles

Back 100

True

Front 101

The NAM and NAG chains of peptidoglycan are connected by what?

Back 101

tetrapeptides

Front 102

LPS layer is composed of a polysaccharide called the ______ and a lipid part called the ______, which has toxic properties, ie. is the endotoxin.

Back 102

-antigen O
-lipid A

Front 103

T/F: endospores can stay resistant for years and are able to begin to grow as soon as they are placed
in suitable environmental conditions

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True

Front 104

Common forms of virus transmission are:

Back 104

-inhalation of droplets
-in food and water
-direct transfer
-bites of arthropods

Front 105

Types of Viral Infection

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1. Lytic - release of viral particles can destroy the cell- lysis ie. polio or influenza virus
2. Persistant - hepatitis B virus may remain alive and continue to release virus particles at a slow rate
3. Latent - virus remains quiescent and the genetic material of the virus may exist in the host cell cytoplasm ie. herpesviruses or may be incorporated into the genome
(retroviruses)
4. Transformation of normal cells into tumor cells - by introduction into the host genome of a viral “oncogene” or by viral proteins that induce cells to divide

Front 106

Innate Defense Mechanisms

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1. Inflammatory response
2. Fever
3. NK Cells
4. Phagocytic Cells
5. Soluble Mediators

Front 107

Inflammatory Respone

Back 107

-infected/injured cells release chemicals that send an alarm out to the WBC of your body calling them to come to the site of infection
-vasodilation of blood capillaries heading towards infection to aid migration of WBC to site
-capillaries carrying blood away from site are constricted
-incr'd permeability of capillaries allowing phagocytes to reach site of infection, leading to redness, swelling
-blood clots around site prevent microbe byproducts from spreading to other parts forming an abscess
-pus consists of dead inflammatory cells and tissue cells as well as dead and living microorganisms

Front 108

Fever

Back 108

-optimum growth temp. for most pathogens is 37 degrees
-increase temp to 40 & pathogens cannot grow

Front 109

How is fever produced?

Back 109

-macrophages produce & release a small protein called IL-1
-IL-1 sends signal to hypothalamus to raise body temp.
-endotoxins (LPS layer) from Gram negative bacteria are pyrogens which induce fever & shock

Front 110

NK Cells

Back 110

-large granular lymphocytes which lack conventional surface markers such as Igs and TCRs
-do not attack invading microbes but body cells that are infected by them
-release perforins that puncture the cell membrane of target cell allowing water to enter causing cell to swell and burst

Front 111

granulocytes

Back 111

-neutrophils
-eosinophils
-basophils

Front 112

agranulocytes

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-lymphocytes (B dddddddddddddddddd& T cells)
-monocytes

Front 113

Soluble mediators

Back 113

-Complement proteins that kill microbes
-lymphokines - soluble proteins produced by T cells
ex. IL-2 and Interferon

Front 114

Complement system

Back 114

-composed of over 20 proteins
-these proteins circulate in blood in an inactive state
-attach to membrane of encountered bacteria
-proteins form a complex of proteins called the MAC
-insert small holes into membrane of bacteria

Front 115

MAC

Back 115

membrane attack complex formed by conjugation of 20+ complement proteins

Front 116

IL-2

Back 116

-released by T helper cells
-major player in immune response
-activates B cells to proliferate

Front 117

Interferon

Back 117

-produced by virally infected cells
-released to the surrounding medium
-causes uninfected cell to synthesize a protein which inhibits infection by the virus by degrading its mRNA

Front 118

Antibodies and TCRs differ in the way they recognize antigen. Explain.

Back 118

-Antibodies: recognize antigens in solution or on a cell surface and in the proteins native (intact)state
-TCRs: recognize antigen in association with MHC molecules on cell surfaces and the antigen is not in its native state. It is processed or degraded so that it is only a small fragment of original antigen

Front 119

antigen processing

Back 119

refers to the degradation of antigen into peptide fragments which become bound to MHC I and II molecules

Front 120

invariant chain

Back 120

a polypeptide which associated with (covers)
MHC II molecules in the rough ER in order to prevent the binding of MHC II to intracellular peptides there. These are to be bound by MHC I, which is also in the ER

Front 121

MHC I and II are synthesized in the ______.

Back 121

rough ER