E3: L21 Flashcards
Tcells originate in the __ and mature in the __ __
thymus, bone marrow
what cells go to the thymus from the bone marrow (not just Tcell)
Lymphoid progenitor cells
where do lymphoid progenitor cells become thymocytes
thymus cortex
what 2 cells do thymocytes contact within the thymus medulla
dendritic and thymic epithelial cells
what are the 4 charesterics of DN (double negative) Thymocytes
- No CD4 or CD8 expression
- go through 4 DN stages
- Proliferate under IL-7
- TCRs develop to recognize specific epitopes
what 2 charesterics must be present of TCRs for them to be fully functionsl
double Pos (DP), express CD4 and CD8
cortical epithelial cells screen what type of thymocytes
DP
what type of epithelial cell expresses both MHC1 and 2
cortical epithelial cells
if DP thymocyte has a strong binding with MHC1 it is ___ committed
CD8+
if DP thymocyte has a strong binding with MHC2 it is ___ committed
CD4+
if DP thymocyte has a weak interaction
apoptosis
positive selection is cells that
recognize either MHC 1 or 2
T/F: can DP cells be single positive for either CD4 or CD8?
T
in negative selection, the interaction between what 2 things is occuring
self-peptides, MHC interactions
what is another name for negative selection
central tolerance
1 of what 2 cells must be present MHC molecules for negative selection
mTEC or bone marrow derived APCs
only cells that pass positive and negative selection are released as
Naive T Cells
Positive selection –>
about recognition of ___ –>
___ mediate, they express __ MHC 1 and MHC 2 –>
__ ___ have the ability to recognize self
MHC, cTEC, both, T cells
Negative selection –>
is about ___ of ___ –>
____ and bone marrow derived ___ mediate, __ binding too strong or too weak –>
Self-___ cells are removed
recognition of self, mTECs and APCs,
TCR, self-reactive
As the quantity of thymocytes decrease, TCR affinity ___
increases
high TCR affinity means
thymocyte doesn’t bind too tight/loose to MHC 1 or MHC 2
tolerance is the prevention of an immune response against ___ structures
self
___ tolerance - deletion of lymphocytes before they mature
central
where does central tolerance occur
primary lymphoid organs
in central tolerance, ___ cells are selected and later used to regulate the immune response
Thymic regulatory T cells
___tolerance occurs outside bone marrow and thymus (primary lymphoid organs)
peripheral
peripheral tolerance occurs vis induction of what cell
pTreg
___ selection occurs with the recognition of foreign antigens
clonal
__ tolerance is deletion of cells or induction of pTreg cells for those cells which recognize self antigens
peripheral tolerance
___ cells negatively reg immune responses
Treg
name for antibodies that induce tolerance
tolerogens
3 things that can occur when T cells interacting with tolerogens
apoptosis, become anergia, regulated by Treg secretions
can tolerogens deplete pro inflammatory cytokines
yes
can tolerogens help to shut down allergic responses
yes
can tolerogens inhibit APCs
yes
can tolerogens secrete inhibitory cytokines
when tolerogens bind Ag-MHC 2 via TCR the effect is
down regulated immune response
when tolerogens secrete inhibitory cytokines, the effect is
decreased inflammtion
The following mechanisms Promote ___
fetal exposure
oral exposre
high antigen doeses
intravenous
low costimulation levels
immature or unactivated APCs
inhibitory cytokines or surface markers
