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BIOL 1103 Lecture Notes - Lymph Node, Lysosome, Mhc Class Ii

1 pages36 viewsFall 2012

Course Code
BIOL 1103
Tamy Superle

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Outline of Lecture 12
Dendritic Cells (and other Antigen Presenting Cells)
I. Overview
- Professional APCs are DC, macrophages, B cells; express MHC II
- DCs are the most efficient APC for primary immune response
II. DC Life Cycle
0) DC progenitors migrate from bone marrow to peripheral tissues
1) Immature DC’s continually sample environment until Ag is encountered
- Active MHC II synthesis, expressed intracellularly
- Active macropinocytosis to sample environment (inefficient)
- Sampling aided by adsorptive endocytosis using PRRs
- Regulated: by GM-CSF, by LPS, TNF, IL-1
- Maturation stops Ag sampling, MHC II expressed on surface and gives snapshot
of Ag’s that were present
2) Migration to secondary lymphoid organ (e.g. lymph node, spleen)
3) Ag presentation to T cells and possible activation of primary immune response
- Sampling of passing T cells; costimulatory molecule expr on DC
- Stable interactions form with Ag-specific T cells (especially CD4+)
- Can also activate CD8+ Tc cells (superactivated DC), cause Th cell
differentiation through IL-12, activate B cells
- May play role in T cell tolerance by presenting Ag without signal 2
III. Other APC’s are more important in secondary immune response
A) Macrophages: FcR-mediated adsorptive endocytosis, but differs from DC in
that Ag’s are completely degraded in lysosomes
B) B Cells: Ig-mediated adsorptive endocytosis
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