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Flashcards in Dendritic Cells Deck (16):

where are immature DCs found

periphery e.g. skin and mucosa


what qualities do immature DCs possess

efficient antigen capture but poor presentation


upon activation by danger signals, where do DCs go

secondary lymphoid tissues to present antigen to T cells


what qualities do mature T cells possess

inefficient at antigen capture but efficient at presentation


describe antigen capture by macropinocytosis

ruffles form on the surface of the dendritic cell. these extend and fuse with PM trapping cytosolic contents. these then form a macropinosome which moves into the cell, delivering the contents. This enables the non specific uptake of large amounts of antigens in the fluid phase


Describe the types of receptor involved in receptor mediated endocytosis by DCs

C type lectins such as the mannose receptor and DEC205 recognise glycosylated proteins. Fc receptors such as FcgRI bind to the Fc portion of antibodies. scavenger receptors such as Cd36 binds apoptotic bodies and receptors for HSPs bind Hsc70 and gp96 from tumour cells or infected cell.s


describe receptor-mediated endocytosis in DCs

ligand binding to the receptor leads to endocytosis in a clathrin coated pit and the formation of an endosome


what are DCs able to phagocytose

almost any bacterium, yeast cells, fungal hyphae and apoptotic and necrotic bodies


which direct innate signals are involved in dendritic cell maturation

toll like receptor binding to ligands.
TLR2 binds Gram+ cell wall components
TLR4 binds LPS in gram- basteria
TLR5 binds flagellin
TLR 9 binds DNA with unmethylated CpG dinucleotides


which indirect innate signals are involved in dendritic cell maturation

molecule secretion triggered by pathogens such as TNF-a. IL1b and PGE2


what is the immediate result of DC activation

increased macropinocytosis however levels return to normal after 1 hour


what are DCs in the skin known as

langerhans cells


upon activation of langerhans cells, what happens

adhesion molecule E cadherin is down regulated in keratinocytes to reduce interactions. Langerhans cells migrate through the dermis into the afferent lymphatic vessels to the lymph node where it hones into T cell concentrated areas. Homie is mediated by up regulation of CCR7 which binds CCL21 expressed by endothelial cells of lymphatic vessels and CCL-19 which is expressed by stromal cells in the T cell zone of lymph nodes


How is antigen presentation via MHC2 molecules regulated by maturation

in immature DCs the low activity of the vacuolar proton pump leads to high endosomal/lysosomal pH and high levels of cystatin C, a protease inhibitor, leads to low protease activity. MHC2 molecules are also rapidly endocytosed. In mature DCs the opposite results in high protease activity and limited endocytosis as well as a transient increase in MHC2 synthesis upon maturation


How is antigen presentation via MHC1 molecules regulated by maturation

in immature DCs there is just moderate expression of MHC1 molecules and MHC1 components such as TAP, tapasin and the immunoproteasome whereas in mature DCs these are expressed at high levels.


what is meant be cross presentation

DCs have a unique capability to present antigens which do not infect DCs in order to activate naive CD8 cells