L1 - Dendritic cells Flashcards
What are the 3 mechanisms that enable the sample and capturing of material?
- macropinocytosis
- receptor mediated endocytosis
- phagocytosis
What is macropinocytosis?
larges vesicles - plasma membrane
immature dendritic cells
non-specific
ruffles
What receptors do dendritic cells express?
C-type lectins
Fc receptors
Scavenger receptors
HSP receptors
What is phagocytosis?
receptor mediated uptake of large particles
receptor engagement
What are the 2 types of danger signals that trigger dendritic cell maturation?
DIRECT signals
INDIRECT signals
What are direct signals?
recognised by TLRs
TLR2 - gram+
TLR3 - dsRNA
TLR4 - LPS gram-
TLR5 - flagellin
What are indirect signals?
triggered by pathogens/ tissue damage
tumour necrosis factor-a
interleukin-1b
prostaglandin E2
When does TLR activation increase macropinocytosis?
immediately after stimulation
Where do dendritic cells migrate from?
epidermis - dermis - lymphatic vessels - lymph node
What are the 3 things involved in the migration of dendritic cells?
langerhans cells interact with keratinocytes via E-cadherin
CCR7 - CCL21, CCL19
What are the 2 chemokine ligands of CCR7?
CCL21 - endothelial cells of lympathic vessels
CCL19 - stroll cells in T cell zone of lymph nodes
How are antigens presented by dendritic cells
ONLY cell to present antigens to naive CD4 (MHC II) and CD8 (MHC I)
What is antigen presentation like in immature dendritic cells?
antigen presentation switched OFF
low protease activity = inefficient chopping up chains for antigens
What is antigen presentation like in mature dendritic cells
antigen presentation switched ON
high protease activity = efficient chopping up chains for antigens
What is cross presentation (dendritic cells)?
can present exogenous antigens
important for initiating adaptive immunity
