Quiz 4 Part 1 Flashcards
name similarities that T cells have to B cells
express highly variable ANTIGEN SPECIFIC receptors
receptors are produced by gene rearrangements (like somatic recombination)
express only a single type of receptor on each cell
the receptor on the T cell resembles the fab fragments
which are more diverse — T cells or B cells?
T cells.
Do T cells and B cells differ in the antigens that they recognize?
yes!
T cells recognize small peptides while B cells recognize structural components
Is there a secreted form of a T cell?
no — only receptor
does somatic hypermutation and isotype switching happen in T cells?
no
thoroughly explain the structure of a T cell receptor
very similar to a fab fragment
there is a variable region, constant region, and a transmembrane region. There is a cytoplasmic tail that branches off from the transmembrane region and sticks into the cytoplasm
there is an alpha chain and a beta chain.
hypervariable loops that serve as the antigen binding site
the alpha chain of a T cell receptor is similar to the ____ chain of an antibody
the beta chain of a T cell receptor is similar to the ____ chain of an antibody (B cell receptor)
alpha chain = light chain. undergoes a SINGLE somatic recombination event (VJ recombination)
beta chain = heavy chain. Undergoes TWO somatic recombination events. (dj, then vdj
What enzyme carries out recombination in T cells?
same as B cell — RAG complex and DNA recombinases
Does junctional diversity also exist in T cells?
yes! (P and N nucleotides)
What is the name of the disease in which the person has NO RAG PROTEINS
SCID (severe combined immunodeficiency disease)
What is the name of the syndrome in which the person has PARTIAL RAG activity
Omenn syndrome
is somatic recombination happening on DNA or RNA
DNA
T cells undergo virtually the same somatic recombination as B cells. However, what is the difference
T cells have more distinct gene segments
Which have more diversity —– T cells or immunoglobulins?
T cells
Which has more variability for the “J” (joining) segments —– alpha chain or beta chain?
alpha chain has more variability for the joining segments
Can T cell receptors be expressed on the cell surface without help?
NO – it needs help
what “helpers” aid the T cell receptor in being expressed on the surface
the T cell receptor associates with 4 invariant membrane proteins
3 in CD3 complex, called CD3Y (gamma), CD3delta, and CD3 epsilon
the TCR complex is assembled from how many polypeptides?
break it down
8 polypeptides
alpha and beta chains (2)
2 CD3episolon (2)
1 CD3delta (1)
1 CD3gamma (1)
2 zeta chains (2)
what are the functions of:
a.) the alpha and beta chains
b.) CD3epsilon, CD3delta, CD3gamma, and the zeta chain
the alpha and beta chains bring about antigen recognition
the others bring about signal transduction
TCR’s can either have alpha and beta chains or __ and ___ chains
gamma and delta
which are made more:
alpha and beta chains
or
gamma and delta chains
alpha and beta
alpha matches with _____ and beta matches with ____
alpha —> gamma
beta —> delta
Can a t cell express alpha and delta?
NO
it’s either alpha and beta OR gamma and delta
cant be both
which is more diverse (has more gene segments)
alpha and beta or gamma and delta
alpha and beta are more diverse
gamma:delta TCR’s are present in around what % of T cells?
less than 5%
where are gamma:delta TCR’s mainly found?
in TISSUES
they don’t really circulate in the blood/lymph
TCR’s recognize ______ as their ligands
short peptides
what presents these short peptides to the TCR?
The MHC COMPLEX
How are these short peptides that are presented to the T cell by the MHC complex generated, and what is the term for this?
these peptides are generated from the degradation of pathogen proteins.
this is called ANTIGEN PROCESSING
What does MHC stand for
major histocompatibility complex
“TCR can only bind antigenic peptide when peptide is bound to MHC proteins”
what is the term for this?
antigen presentation
what is the name of the cell that presents the peptide/MHC complex to the TCR?
APC —- professional Antigen-Presenting Cell
what are some examples of professional APC’s (antigen-presenting cell)
B cells, macrophages, and dendritic cells
MHC molecules can only get to the surface of the cell when….
it is bound to peptide
Each MHC molecule can bind how many peptides?
ONLY ONE
What are the 2 types of MHC molecules and explain the difference between them
MHC Class 1
MHC Class 2
MHC Class 1 contains an accessory protein called Beta-2 microglobulin. it recognizes INTRACELLULAR PATHOGENS
MHC class 2 does NOT have an accessory protein. it binds EXTRACELLULAR PATHOGENS
MHC Class 1 binds peptide antigen in the…..
ER
MHC class 1 presents the peptide to which cells?
presents INTRACELLULAR PATHOGENS to cytotoxic T cells (CD8+)
MHC Class 2 presents the peptide to which cells?
MHC class 2 presents EXTRACELLULAR PATHOGENS to CD4+ T cells
MHC Class 2 binds peptide antigen where?
in endosomes
what is the purpose of CD8+ T cells?
cytotoxic T cells that kill infected cells
what is the purpose of CD4+ T cells?
helper T cells that activate macrophages to enhance phagocytosis and cytokine/chemokine production
Which T cell stimulates B cells to promote affinity maturation of antibodies?
CD4+ T cells
HIV selectively infects ____ T cells
CD4+
what are TCR coreceptors?
CD4 and CD8
If a T cell is contacting a virus-infected cell, what type of T cell is it and what class of MHC presented the antigen?
antigen was presented by MHC Class 1 and CD8+ T cell made contact
T cells function by making ______ with other cells and inducing them to change
CONTACT
