lecture 2b Flashcards
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.
bacteria
viruses
skin
gastrointestinal tract
respiratory tract
immature dendritic cells
Langerhans
epidermis
mature dermal dendritic cells
antigen
lymphatic vessels
lymph nodes
T cells
MHC molecule binds _, and only when a
_ then: travels from
_ to the _.
At the cell _, the _ is recognized by the _
a single peptide
peptide-bound MHC
inside
cell surface
surface
MHC-antigen complex
TCR
Antigens recognized by TCR
are _ ranging from
_ amino acids in length
short peptides
8-25
An MHC only exists on the cell surface when it _.
In the absence of infection, MHC molecules will _
forms a unit with a peptide
only carry self-peptides
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 _.
negative selection
thymus
negative selection
eliminated
autoimmunity
two broad kinds of pathogens:
intracellular and extracellular
which MHC presents to CD4+ T cells?
class II
which MHC presents to CD8+ T cells?
class I
which T cells bind to MHC class I?
CD8+ T cells
which T cells bind to MHC class II?
CD4+ T cell
for which pathogens the MHC I-CD8 T cell complex forms? and how are they degraded?
intracellular
Degraded in the cytosol (via proteosome)
for which pathogens the MHC II-CD4 T cell complex forms? and how are they degraded?
extracellular
Degraded in phagolysosomes
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.
virus-infected
bacteria-infected
intracellular
direct
their death
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 _.
activating other immune cells
macrophages
cytokines
macrophages
extracellular
B cells
B cells
plasma cells
high-affinity antibodies
binding and neutralizing extracellular
other immune components
CD4 and CD8 are T-cell _
co-receptors
Any cell harbors _ to degrade misfolded proteins;
activated cells also express specialized _
constitutive proteasomes
immuno-proteasomes
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.
constitutive
cytokines
interferons
immuno
more
Constitutive Proteasome: This is the _ form found in cells, involved in _ proteins that are damaged or no longer needed.
regular
degrading
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.
PA28 activator
Antigen processing for the class I MHC pathway
requires two specialized instruments:
TAP (Transporter associated with
antigen processing): let peptides into ER
Proteasome
TAP is associated with _ in the endoplasmic reticulum membrane, which guides the peptide loading of MHC class I
chaperone proteins
Peptide editing: peptides are trimmed by _ (endoplasmic reticulum aminopeptidase) to stably fit MHC-I molecule resulting in _ long peptide
ERAP
8-10 amino acids
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
conformational change
tapasin
The two ends of the peptide
are _ into the
pockets at each end of the
MHC-I groove
pinned down
