T cell activation Flashcards
(43 cards)
activation is not initiated until the second signal is received by a co-stimulator ___________________________ between the APC and naïve T cell
receptor-ligand binding pair
what is the purpose of plasmacytoid dendritic cell?
involved in the early stages of innate immune response secreting anti-viral cytokines IFNa and IFNb. They are key players against viral infections
what is the purpose of myeloid dendritic cells?
involved in T cell activation. These dendritic cells are found throughout the tissues
of the body in sites of antigen exposure (i.e. skin)
what is the dendritic cell in the skin?
langerhans cell
what are immature dendritic cells?
dendritic cells that have not been activated tend to express high levels of antigen receptors for pathogens (i.e. Toll-like receptors and phagocytic receptors), but low levels of MHC on their cell surface
what happens if a mature dendritic cell already resides in secondary lymphoid tissue?
it would initiate Ag presentation to T cells and B cells accompanied by the secretion of cytokines (i.e. IL-12
what would happen if the mature dendritic cell resided in peripheral tissues like Langerhans cell?
in addition to the upregulation in MHC class I and MHC class II molecules, the dendritic cell would upregulate adhesion molecules and chemokine receptors to aid in its migration into the lymphatics and ultimately to the draining lymph nodes to present processed Ag to the circulating naïve T cells or memory T cells, if the host had encountered the antigen previously
how does the dendritic cell become mature?
Upon recognition and internalization of foreign antigens (i.e. pathogens), the dendritic cell is
activated and changes it cell surface protein expression molecules toward an increase in MHC molecules bound with linear peptide Ag
what do activated APCs express?
a multitude of MHC molecules with different linear Ag peptides with the potential to activate many different T cells
why does MHC and TCR have such a low affinity binding event?
association between the MHC and TCR is based on such a small peptide and only components (i.e. amino acid sequences) of that peptide.
what stabilizes the MHC-TCR binding and also lowers the threshold of T cell activation?
additional binding of the co-receptor (i.e. CD4) to the invariant portion of the MHC
what is B7-CD28 binding required for?
second signal and T cell activation
what is upregulated upon activation of T cells?
CD152
what deactivates the T cell with expression of CD152?
if bound by CD80 or 86
what is upregulated when the T cell becomes activated and upregulating the expression of the CD80 or CD86 molecules and also has important role when T cells interact with B cells in antibody synthesis?
CD154
list 3 adhesion molecules
CD54 (ICAM-1)-CD11a/CD18 (LFA-1), CD58 (LFA-3)- CD2, and LFA-1-CD50 (ICAM3)
define immunologic synapse?
collective association of the MHC-TCR, co-receptors and adhesion molecules between the
APC and T cell
how do we creen these cell surface
molecules to evaluate the different stages of cell activation as well as help determine if there is a defect cell surface molecule when we suspect some abnormal immune response?
flow cytometry
what does linker for activation of T cells (LAT) serve as?
an adapter protein to bind more proteins such as SLP76. This protein when bound promotes the reorganization of cellular actin as well as binding to phospholipase Cγ1 (PLCγ1)
what does linker for activation of T cells (LAT) serve as?
an adapter protein to bind more proteins such as SLP76. This protein when bound promotes the reorganization of cellular actin as well as binding to phospholipase Cγ1 (PLCγ1)
Upon binding of the MHC-peptide TCR, _________ kinases Fyn and Lck (members of Src family) are activated via dephosphorylation by membrane-bound protein CD45 and are drawn to the ITAMS on the cytoplasmic domains of the CD3 and ζ chains.
tyrosine
______ is a key mediator of 3 distinct cell signaling pathways all of which result in the activation of transcription factors
PLCγ1
The impact of the second signal B7-CD28 at the intracellular level promotes lipid rafts to
transport additional kinases and other molecules to the TCR site to enhance signaling. In addition, binding of B7-CD28 attracts the enzyme phosphatidylinositol-3 (PI3). It is believed that these combined events serve to promote ____ synthesis by increasing the rate of ____ gene transcription
IL-2
how has the calcineurin pathway been used as a therapeutic target?
to downregulate T cell activation following tissue/organ transplantation
