EXAM 2 T Cells: Receptors, MHC, and Antigen Recognition Flashcards
what are the 6 types of effectors T cells?
- CD8 cytotoxic T cells
- CD4 Th1 cells
- CD4 Th2 cells
- CD4 Th17 cells
- Tfh cells
- CD4 regulatory T cells
what are the functions and targeted pathogens of CD8 cytotoxic T cells?
- functions in adaptive immune response: kill virus infected cells
- pathogens: viruses and some intracellular bacteria
what are the functions and targeted pathogens of CD4 Th1 cells?
- function in adaptive immune response: activate infected macrophages, provide help to B cells for antibody production
- pathogens: microbes that persist in macrophage vesicles, and extracellular bacteria
what are the functions and targeted pathogens of Cd4 Th2 cells
- functions in adaptive immune response: provide help to B cells for antibody production, especially switching to IgE
- pathogens: helminth parasites
what are the functions and targeted pathogens of CD4 Th17 cells?
- functions in adaptive immune response: enhance neutrophil response, promote barrier integrity
- pathogens: klebsiella pneumoniae, fungi
what are the functions and targeted pathogens of Tfh cells?
- functions in adaptive immune response: B cell help, isotype switching, and antibody production
- pathogens: all types
what is the function of CD4 regulatory T cells in the adaptive immune response?
suppress T cell responses
T cells are defined by ___
T cell receptors (TCRs)
TCRs primarily bind ___
polypeptides
the TCR is expressed on the ___, and is never ___
- cell surface
- secreted
TCRs are similar in structure to ___
immunoglobulins
do TCRs have effector functions?
no
TCRs do not recognize ___ in isolation
antigens
TCRs interact with ___ presented antigen
MHC
TCRs are ___ detectors
incidence
what are the two classes of TCR?
alpha:beta T cells and gamma:delta T cells
describe alpha:beta TCRs
- alpha and beta chain
- “classic” T cell
- adaptive immunity
- common in circulation, not tissues
- develops and matures in the thymus
- positive and negative selection
describe gamma:detal TCRs
- gamma chain and delta chain
- not involved in classic adaptive immunity
- monitor tissue health
- common in tissues, not circulation
- develops, but does not mature in the thymus
- limited positive and negative selection
- one class
can T cells express more than one TCR type?
no, they can only express one type
describe the rearrangement of the alpha chain
- V, J, C segments
- junctional diversity
describe the rearrangement of the beta chain
- V, J, D, and C segments
- junctional diversity
how many hypervariable/complementarity-determining regions are there per chain?
3
What happens if you have a mutation in the RAG 1/2 complex?
immunodeficient in TCRs, so T cells will not develop
TCRs require the ___ complex for signal transduction
CD3
plasma membrane TCR expression does not occur without the CD3 complex
do T cells or B cells have more diversity?
T cells
CD3 complex mediates ___
TCR signaling
what are CD3 complexes?
proteins that mediate the majority of TCR signaling
how do MHC complexes present antigens to TCRs?
describe MHC class I
- intracellular antigen (proteins within the cell)
- nearly all cells
- alpha chain and beta2 microglobulin
- ER antigen loading
- CD8 co-receptor
describe MHC class II
- internalized antigen (internalized by macrophage or phagosome)
- antigen presenting cells
- alpha and beta chains
- vesicular ER loading
- CD4 co-receptor
MHC bind peptides for ___
TCR presentation
do all cells express MHC?
almost…nearly all cells express some form of MHC
MHC is considered “promiscuous”; what does that mean?
a TCR can bind a lot of different types of MHC class I and II
what is the human leukocyte antigen (HLA) complex?
another word for the MHC complexes in humans
T or F:
MHC class I and II have the same antigen presentation
false, they have different antigen presentation
describe antigen presentaiton by MHC class II
- extracellular antigen is phagocytosed
- peptide production in phagolysosome
- peptide binding by MHC class II
- MHC class II presents peptide at cell surface
describe antigen presentation by MHC class I
- intracellular antigen is processed to peptides in the proteasome
- peptide transport into ER
- peptide binding by MHC class I
- processed through golgi body, then MHC class I presents peptide at cell surface
describe MHC class I antigen loading in the ER
- intracellular peptides of 8-10 residues
- peptides trimmed before expression
- allows detection of intracellular infection
describe MHC class I crosspresentation of endocytosed antigen
- MHC II presents most endocytosed antigen
- important in naive CD8 T cell activation
describe MHC class II antigen loading into vesicles
- by now, the MHC class II molecule has already gone through processing in the ER and golgi body
what is CLIP? how does it prevent self antigen presentation
- CLIP - class II associated invariant chain peptide
- any peptide that has a greater binding affinity for MHC II (NOT self antigen) will cause HLA-DM to remove CLIP and allow that peptide to bind
describe the T cell synapse of CD8 T cells
co-receptors dictate MHC specificity
describe the T cell synapse of CD4 T cells
co-receptors dictate MHC specificity
___ dictate MHC specificity
co-receptors
T cells have ___ and ___ effector functions
direct and indirect
describe the effector functions of CD8 T cells on virus infected cells. is this direct or indirect?
direct
describe the effector functions of CD4 T cells on macrophage. is this direct or indirect?
indirect
describe the effector function of CD4 T cells on B cells. is this direct or indirect?
indirect
which cells express MHC class II?
antigen presenting cells
dendritic cells, B cells, and macrophage
CD8 binds the ___ domain of MHC class ___
- alpha-3
- I
CD4 binds the ___ domain of MHC class ___
- beta-2
- II
which cells express MHC class I?
T cells, B cells, macrophages, dendritic cels, neutrophils, and non-hematopoietic cells (liver hepatocytes, kidney epithelium, and brain)
which cells express both MHC class I and MHC class II?
B cells, macrophages, and dendritic cells
