Chapter 5 - T cell (Exam 3) Flashcards
similarities of antibodies to TCR
both have 2 chains
1 constant region
gene rearrangment
differences of antibodies to TCR
Ab is wide range, TCR is peptides only
no further change in TCR after Ag stimulation
Ab has 2 binding sites, TCR has 1
TCR is membrane bound only
unlike antibodies, TCR is membrane bound only. This means its function is to only _____________ and it has no ____________
recognize the antigen
no effector function
TCR resembles _______ of an antibody
Fab
somatic recombination in TCR
rearrange the beta chain
only 1 Ca gene segment
RAG proteins are essential for
adaptive immunity
omenn syndrome
partial loss of RAG protein activity
fatal
treatment for SCID and Omenn syndrome
bone marrow transplant at birth
MHC heterozygosity delays
AIDS progression
populations maintain a _________ of HLA Class I and II ______________
diversity
allotypes
gamma chain delta chain T cell receptor
1-5% of T cells
function is less defined
can bind peptide without MHC
the delta chain has more ___________ than the beta chain
junctional diversity
the delta chain locus is located between
V, J of alpha chain locus
TCR has more ___________ than Ig in somatic recombination due to _____________
diversity
J segment
antigen processing
degrading of pathogen derived proteins into peptides
antigen presentation
binding of peptide by MHC and display at cell surface
MHC class I targets ____________ by binding ____________
intracellular pathogens
cytotoxic T cells
MHC class II targets ______________ by binding _______________
extracellular pathogens
helper T cells
professional APCs
they have the highest expression on MHC class I and II
can present the best to T cells
which types of cells are professional APCs
B cells
Macrophages
Dendritic Cells
class I MHC is on
almost every cell
2 effector functions of T cells
kills infected cells (CD8)
helps other cells (inc microbicidal activity of macrophages or B cell differentiation)
MHC II also known as the
vesicular system
MHC II is continuous with
the extracellular fluid
MHC I is in the
cytosol
MHC is ___________ because it can bind
promiscuous
many different peptides
Do MHC I and MHC II bind the same peptides?
NO!
they bind different types
immunoproteasome
modified subunits and cap proteins
makes peptides with hydrophobic or basic terminus
For MHC I, the __________ degrades cytoplasmic proteins into ___________ to present to _________ T cells
proteasome
peptides
CD8
TAP
transporter associated with antigen processing
transports peptides into ER so it can bind MHC I
bare lymphocyte syndrome
TAP nonfunctional, no peptides enter ER
very few MHC I on surface
In MHC II, the ___________ pathogen peptide is generated in _________________
external
endocytic vesicle
how does proteases to degrade pathogen proteins into peptides?
the phagosome fuses with lysosome
Even without infection, MHC I and II are constantly presenting ___________ that should not be recognized by TCR
self peptides
2 stages of antigen presentation
T cell is primed by dendritic cell
T cell performs effector function
priming of T cell by dendritic cell occurs in
secondary lymphoid tissue
T cell modification of other cells occurs at
site of infection, secondary lymphoid tissue, periphery
CTL response (MHC I)
virus infects dendritic cell
priming of naive CTL -> effector
effector CTL migrates to infection site and kills
Helper response: MO activation
dendritic cell phagocytoses pathogen
migrates to lymph node and activates naive helper T cell
effector T cell migrates to infection site and helps MO there
Helper response: B cell activation
same steps as MO activation except effector T cell helps B cell in lymph
Cross presentation
APC captures virus by extracellular pathway then prevents complex to CTL of intracellular pathway
intracellular pathogen degraded by extracellular response
can pathogens prevent processing and presentation?
YES!
MHC has
inherited diversity
very different _______ molecules are usually expressed on APCs from ______________
MHC
different people
2 sources of inherited diversity of MHC
different gene families
genetic polymorphism
different gene families
each person has multiple genes for MHC Ia chain and HC II a and b chains
isotopes are different
proteins in a gene family
genetic polymorphisms
multiple forms of these genes in one person vs another
allotypes
different proteins encoded by different alleles
types of genetic polymorphisms
highly polymorphic
oligomorphic
monomorphic
MHC Class I isotypes
HLA-A HLA-B HLA-C
MHC class II isotypes
HLA-DP
HLA-DQ
HLA-DR
polymorphism in MHC alleles is
uniquely large
differences in MHC are usually in the
peptide binding groove
there is ______ polymorphism in MHC allotypes
high
in class II MHC, each alpha and beta chain are encoded by
separate genes
in class I MHC, each alpha chain is encoded by
a separate gene (A,B,C)
MHC alleles are
codominant
specific allotropes expressed are determined by
polymorphisms a person has
HLA haplotype
particular combination of HLA alleles found on chromosome 6 in a single human
is it likely that 2 people will share the same HLA haplotype?
VERY UNLIKELY
minimum HLA isoforms
in homozygote
3 class I, 3 class II
maximum HLA isoforms
in heterozygotę
6 class I, 12 class II
having multiple different HLA alleles
improves immune response
amino acid differences in MHC occur
at sites that contact peptide or TCR
MHC restriction
each T cell receptor recognizes a unique peptide:MHC combination
the specificity of T cells is dictated by
the distinct MHC molecules
heterozygotę advantage
covers more types of peptides to present
alloreactive T cells
attack a transplanted organ
alloreactive antibodies
produced by mother during pregnancy
react to HLA molecules in fetus specific to father
can also attack a transplanted organ
