Flashcards in cytotoxic T cells Deck (84)
How is endogenous antigen broken up beofre entry to the ER?
Describe the peptide binding groove on MHC?
slightly curved beta sheets as a base with two alpha helices on top
How many amino acids can the MHC I bind?
How many amino acids can the MHC-II bind?
How are TCRs formed?
by rearranging non-continous gene segments
What is the most important costimulation give to naive T cells?
What happens to a naive T cell if there is peptide recognition in the absence of costimulation?
activation induced cell death or anergy
What is the function of CTLA4?
binds CD80/86 but is inhibitory
What is the difference between the antigens picked up in the spleen and lymph nodes?
spleen will pick up bloodstream antigens whereas lymph nodes will pick up antigen in tissues
How can dendritic cells be activated?
TLRs and other PRRs; tissues damage or cytokines produced during the inflammatory response
Where are dendritic cells foudn in the lymph nodes?
cortex of the lymph node in the T cell areas
Where are macrophages foudn in the lymph ndoes?
throught the lymph node but concentrated mainly in the marginal sinus and medullary cords
What happens in the marginal sinus of hte lymph node?
afferent lymph collects before percolating through the lymphoid tissue
What happens in the medullary cords of the lymph nodes?
effect lymph collects before passing via the effect lymphatics into the blood
What is the function of plasmacytoid DCs?
sentinels for viral infections and produce large amoutns of type I IFNS
What receptors do dendritic cells have for phagocytosing antigen?
complement; Fc; C-type lectins
What is the nonsepcific method that dendritic cells have for the uptake of antigen?
What is the benefit of dendritic cells using macropinocytosis in addition to phagocytic receptors to ingest antigen?
microbes that have evolved strategies to escape recognition by phagocytic receptors e.g bacteria with thick capsules are ingested
What is cross presentation?
when viral antigens which enter dendritic cells via endocytic or phagocytic vesicles may be diverted to the cytosol for proteasomal degrataion and loaded onto MHC I molecules
what is hte purpose of cross presentation?
viruses that do not directly infect DCs can stimulate the activation of CD8 cells
In what infections are dendritic cells from the site of infection able to transfer antigen to resident dendiritc cells in the lymph nodes ?
herpes simplex or influenza
What chemokine receptor is upregulated in licensed dendritic cells?
What is the function of CCR7 being upregulated by activated DCs?
responds to CCL21 which is produced by lymphoid tissue and facilitiates their migration into local lymphoid tissue; also contributes to their enhanced APC function
As well as MHC and costimualtory molecules CD80 and CD86, what else do activated DCs express?
adhesion molecules e.g DC-SIGN; secrete CCL19
What is the function of CCL19 secreted by DCs?
specifically attracts naive T cells
What cytokine do activated T cells secrete?
What are the functions of IL-2 produced by activated T cells?
maintenance of Tregs; augment T cell proliferation and survival; affects the balance of effector and memory T cells that develop in a primary response to antigen
Which cells produce IFNy?
Th1; NK cells; CD8
By what process do cytotoxic T cells kill tagret cells?
extrinsic or intrisinc apoptotic pathways