T cells 2 Part 1 Flashcards
What do Tk cells do?
kill other cells
What do Th cells do?
help other cells
Where are T cells made?
bone marrow
Where do T cells mature?
in the thymus (T for thymus)
T/F: T cells circulate in the blood and lymph.
true
T/F: T cells cannot enter tissue
false; they can
What are the antibody like receptors on the surface of T cells called?
T cell receptors (TCRs)
What do TCRs specialize in?
recognizing protein antigens presented by MHCs (this means the antigen is a peptide)
T/F: there are about 300 million T cells in the body on average.
False; 300 billion, with a B.
What are killer T cells also called?
cytotoxic T cells (CTLs)
How are killer T cells activated?
by MHC I being presented on cells
T/F: most cells in the body can present antigens to CTLs via MHC class II molescules.
False; should say MHC I molecules
What connects to the target cell and triggers it to commit suicide killing the cell and the virus inside it?
Killer T cells/CTLs
What activates Helper T cells (Th)?
MHC II on Antigen Presenting Cells (APCs)
What is secreted by Helper T cells?
cytokines IL-2 and IFN-y (interferon gamma)
What kind of cells keep the immune system from overreacting?
Regulatory T cells
T/F: regulatory T cells are probably the one part of the immune system that we know the most about.
False; much is still unknown about regulatory T cells
T/F helper T cells do not require activation to perform their function.
False; both helper and killer T cells require activation
What kind of cells help Helper T cells?
APCs (activated dendritic macrophage and B cells)
What must a TCR recognize in order to be activated?
cognate antigen
What must the Co-receptor recognize in order for activation to occur?
MHC (either I or II)
What happens during Co-stimulation?
other receptors recognize other molecules (besides for cognate antigens and MHCs)
T/F: more is known about Helper T cell activation than Killer T cell activation.
True (think alphabetical order)
What happens to T cells that see “self” being presented by other cells?
These die. T cells that would kill self need to go away.
How are T cells anergized?
When T cells recognize self antigen, but do not get co-stimulated they will be rendered inactive or anergized.
What happens to a T cell that sees non-self and gets co-stimulated?
activation
What happens when a TCR recognizes MHC plus self peptides?
T cell commits suicide (apoptosis)
What happens when TCR recognizes cognate antigen on MHC with no co-stimulation?
T cell is anergized (inactivated)
What happens when TCR recognizes cognate antigen on MHC plus co-stimulation?
T cell is activated
T/F: T cells recognize MHC I and/or MHC II molecules.
False; T cells only recognize peptides presented by MHC molecules
T/F: TCRs are more diverse than BCRs.
False; BCRs are more diverse
T/F: All TCRs on mature T cells are identical except for a few exceptions.
True
What are the two types of TCRs?
traditional (alpha beta) ad non-traditional (gamma delta)
T/F:about 95% of TCRs are alpha beta TCRs.
True; the other 5% are gamma delta)
What is the name given to the group of signaling proteins?
CD3
What kind of receptors are expressed by non-traditional T cells?
gamma delta receptors
Where are non-traditonal T cells most abundant?
in the intestine, uterus and tongue
T/F: non-traditional T cells have more diversity than the alpha beta receptors (traditional T cells).
False; they less diversity
T/F: non-traditional T cells are more effective at recognizing protein fragments from invaders.
True, at least around the intestine uterus and tongue they are
T/F: more is known about non-traditional T cells than the traditional T cells.
False; less is known about non-traditonal Tcells
Why are TCR proteins important for actviation?
antigen recognition
Why are co-receptor proteins (CD4 or CD8) needed for activation?
MHC recognition
What co-stimulatory molecules are needed for activation?
B7 proteins on APCs
Why are CD3/CD4 proteins needed for activation?
for signaling
Why is CD28 on Tcells important for activation?
co-stimulation and signaling
Where is the T cell co-receptor CD4 usually expressed?
on helper T cells
What kind of molecule does CD4 attach the TCR to?
MHC II molecules
Where is the T cell co-receptor usually expressed?
on Killer T cells (CTLs)
What kind of molecules does CD8 attach the TCR to?
MHC I molecules
T/F: CD8 signals “likely to help”
False; this is what CD4 signals, CD8 signals “likely to kill”
T/F: Without the co-receptor, the T cell would not know if an APC is presenting protein fragments and needs help (helper T) or if an APC is infected and need to be killed (killer T)
True
T/F: MHC I molecules are eaten by the APC.
False; this is true of MHC II molecules
T/F: MHC I molecules are peptides being made in the cell.
True
What is implied by the CD8 co-receptor?
MHC I
What is implied by the CD4 co-receptor?
MHC II
T/F: CTLs bind to kill.
True
What do B cells, Dendritic cells, and macrophages have in common?
These are all APCs
MHC presents the antigen (peptide) which is recognized by the TCR. What recognizes the MHC? And what sends a signal of this to the nucleus of the T cell?
co-receptor; CD3
T/F: B7 is a receptor molecule on the T cell. When activated, it amplifies the signal and lowers the number of TCR crosslinks needed for activation.
False; this is true of CD28; B7 is a co-stimulatory molecule expressed on the surface of APCs.
What does the combination of co-stimulation molecules depend upon?
the pathogen and the area of the body (regional identity)
T/F: the connection between the receptor and the nucleus of naiive T cells is weak.
true; activation with co-stim creates a better connection.
Once T cells are activated by co-stimulation, many more cholesterol lipid rafts form. What do these lipid rafts contain?
large numbers of signaling molecules
T/F: experienced T cells have few rafts.
False; experienced T cells have many, naive T cells have few.
What is the benefit of Experienced T cells maintaining the lipid rafts?
they don’t need co-stim for reactivation
What is easier, Reactivation or co stimulation?
reactivation because the raft has formed
Dendritic cells may first activate T cells in a lymph node. What re-stimulates/activates T cells once they reach the battle site?
Macrophages
