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Immunology > lecture 2b > Flashcards

lecture 2b Flashcards

1
Q

Extracellular and intracellular pathogens, such as _ and _, enter the body through various sites like the _, _, and _. These pathogens are first captured by _, such as _ cells in the _. These cells then migrate to deeper skin layers and transform into _. They capture the _ and transport it via afferent _ to the _. Here, the antigen is presented to _, leading to their activation.

A

bacteria
viruses
skin
gastrointestinal tract
respiratory tract
immature dendritic cells
Langerhans
epidermis
mature dermal dendritic cells
antigen
lymphatic vessels
lymph nodes
T cells

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2
Q

MHC molecule binds _, and only when a
_ then: travels from
_ to the _.
At the cell _, the _ is recognized by the _

A

a single peptide
peptide-bound MHC
inside
cell surface
surface
MHC-antigen complex
TCR

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3
Q

Antigens recognized by TCR
are _ ranging from
_ amino acids in length

A

short peptides
8-25

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4
Q

An MHC only exists on the cell surface when it _.
In the absence of infection, MHC molecules will _

A

forms a unit with a peptide
only carry self-peptides

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5
Q

self-peptides in the (MHC-antigen complex) are generally ignored by T cells because of the process of _ in the _. During _, T cells that strongly react to self-peptides presented by MHC molecules are _, preventing _.

A

negative selection
thymus
negative selection
eliminated
autoimmunity

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6
Q

two broad kinds of pathogens:

A

intracellular and extracellular

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7
Q

which MHC presents to CD4+ T cells?

A

class II

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8
Q

which MHC presents to CD8+ T cells?

A

class I

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9
Q

which T cells bind to MHC class I?

A

CD8+ T cells

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10
Q

which T cells bind to MHC class II?

A

CD4+ T cell

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11
Q

for which pathogens the MHC I-CD8 T cell complex forms? and how are they degraded?

A

intracellular
Degraded in the cytosol (via proteosome)

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12
Q

for which pathogens the MHC II-CD4 T cell complex forms? and how are they degraded?

A

extracellular
Degraded in phagolysosomes

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13
Q

Cytotoxic T cells (CD8+): These cells specifically target and destroy _ cells, _ cells, or cells harboring other _ pathogens. They make _ contact with these infected cells and induce _, preventing the spread of the infection.

A

virus-infected
bacteria-infected
intracellular
direct
their death

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14
Q

Helper T cells (CD4+): They play a crucial role in orchestrating the immune response by _:

Activation of _: Helper T cells release _ that enhance the ability of _ to engulf and destroy _ pathogens.
Assistance to _: They help _ mature into _ that produce _. They are crucial for _ pathogens, facilitating their elimination by _.

A

activating other immune cells
macrophages
cytokines
macrophages
extracellular
B cells
B cells
plasma cells
high-affinity antibodies
binding and neutralizing extracellular
other immune components

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15
Q

CD4 and CD8 are T-cell _

A

co-receptors

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16
Q

Any cell harbors _ to degrade misfolded proteins;
activated cells also express specialized _

A

constitutive proteasomes
immuno-proteasomes

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17
Q

Normally, all cells contain _ proteasomes that degrade misfolded proteins. However, under the influence of antiviral _ like _, cells can express _ proteasomes, which are _ adept at processing antigens for immune responses.

A

constitutive
cytokines
interferons
immuno
more

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18
Q

Constitutive Proteasome: This is the _ form found in cells, involved in _ proteins that are damaged or no longer needed.

A

regular
degrading

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19
Q

Function Enhancement: the _ can be added to the immunoproteasome to speed up the release of peptides, enhancing the cell’s ability to present antigens and stimulate an immune response effectively.

A

PA28 activator

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20
Q

Antigen processing for the class I MHC pathway
requires two specialized instruments:

A

TAP (Transporter associated with
antigen processing): let peptides into ER
Proteasome

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21
Q

TAP is associated with _ in the endoplasmic reticulum membrane, which guides the peptide loading of MHC class I

A

chaperone proteins

22
Q

Peptide editing: peptides are trimmed by _ (endoplasmic reticulum aminopeptidase) to stably fit MHC-I molecule resulting in _ long peptide

A

ERAP
8-10 amino acids

23
Q

Peptide that binds tightly to
the MHC class I causes
_ that
break the hold of _,
allowing the peptide:MHC I
complex to leave ER in a
membrane-enclosed vesicle

A

conformational change
tapasin

24
Q

The two ends of the peptide
are _ into the
pockets at each end of the
MHC-I groove

A

pinned down

25
Q

In MHC class II, the two ends of
the peptide _ from
each end of the groove

A

extend out

26
Q

Peptides that bind MHC class I
molecules are _ amino acids
in length

A

8-10

27
Q

Peptides that bind MHC class I
molecules are usually _
amino acids long

A

13-25

28
Q

Some virus types do not infect dendritic cells and,
therefore, peptides of these viruses never reach the
cytosol of dendritic cells. These viruses will escape
adaptive immunity by not initiating appropriate antiviral
_ responses.
Solution:
_

A

CD8+ T cell
Cross-presentation

29
Q

cross-presentation:

A

antigen-derived peptides from phagolysosomes
are also presented on MHC class I molecules

30
Q

Cross-presentation
Dendritic cells have the special capability to _.
In this way, dendritic cells will present virus-derived peptides on MHC class I molecules after
_

A

leak peptides from phagolysosomes into the cytosol.
phagocytosis of dying virus-infected cells

31
Q

Leakage/escape
of phagolysosome
peptides into
cytoplasm in DCs:
_

A

Retrotranslocation
to ER

32
Q

All nucleated cells (so, not erythrocytes) can potentially
be _ by viruses. To challenge all virus types, all
cell types must express _ to allow virus
recognition and killing by cytotoxic T cells.

A

hijacked
MHC class I

33
Q

Dendritic cells are the only genuine “professional”
_ cells that pick up and
process and can _

A

Antigen-presenting
activate naïve T cells

34
Q

Macrophages require _ help to _

A

T cell
intracellularly kill ‘obligate’ endosomal pathogens

35
Q

B cells phagocytose and process antigen to require help from _ to produce _

A

effector T cells
antibodies

36
Q

Thymic epithelium cells: These unique cells
express _, which enables _ of the T cell repertoire

A

all human proteins
negative selection

37
Q

While TCRs are incredibly _ and can recognize _ pathogen-derived peptide-MHC complexes, the ability of MHC molecules to physically bind peptides is inherently _.

A

diverse
many different
limited

38
Q

The pool of presented peptides is enhanced by:
1. _
2. _
3. _

A

Promiscuity (the binding of look-a-like peptide types to a single MHC).
MHC isotypes (multiple genes).
MHC allotypes (polymorphisms)

39
Q

Human MHC molecules are called
_ (_)

A

HLA
human leukocyte antigens

40
Q

_ in MHC groove may differ in
characteristics
(hydro-/lipidophilic, basic/acidic, charged, etc) and form the _

A

Anchor amino acids
peptide-binding motif

41
Q

The anchor amino acids bind peptide
antigens with _ (hydro-
/lipidophilic, basic/acidic, charged, etc)

A

matching characteristics

42
Q

Anchor residues are essential
for _
* Positions white boxes at
which the identity of amino
acid sequence can _

A

stable peptide-binding
vary

43
Q

Diversity of MHC molecules in the human
population is due to _

A

multigene family

44
Q

Human cells express MHC gene isoforms:
* _ different class I molecules
(HLA-A, HLA-B and HLA-C)
* _ different class II molecules
(HLA-DP, HLA-DQ and HLA-DR)

A

Three
Three

45
Q

what Contribute to diversity of
MHC class I and II molecules
expressed by an indvidual

A

polygeny (multiple genes) and polymorphism (multiple alleles)

46
Q

Allotypes arise from _
(polymorphisms) and _
(gene conversion).

A

point mutations
interallelic

47
Q

MHC allelic variation is _

A

within peptide-
binding pocket and TCR contact
residues.

48
Q

Each of the class I and class II MHC molecules shows a
_ degree of polymorphism

A

variable

49
Q

Allotypes have different
_
_ of the allotypes
_ within
populations.
For example, HLA02 allotypes
are _ than
HLAA15 allotypes

A

fequencies
Frequencies
vary strongly
far more frequent

50
Q

Different HLA alleles bind different _,
which increases the diversity in antigen presentation

A

pathogen-derived peptides

51
Q

TCRs are very precise
A given TCR that
recognizes a certain
MHC/peptide combination
will not be able to
_

A

recognize the same petide
(X) in the context of
another MHC molecule

52
Q

TCR recognizes foreign antigen only when bound to _

A

particular self-MHC
molecule

Immunology (6 decks)

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