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Mechanism for T cell development and thymic education?
- T cells migrate to thymus from bone.
- First acquire CD 2 and 3 and retained
- Positive selection then negative selection
- 1-2% survive then leave with either CD4 or CD8
Describe the 3 HSC lineages?
- Lymphoid: B and T cells and NK cells (which are share common progenitor with T cells)
- Myeloid: Granulocytes (eo, baso, neutro), monocytes (Dendrites, macrophages), mast cell
- Erythroid: RBC, platelets (from megakaryocytes)
peripheral lymphoid organs
Spleen, LN, tonsils, peyer's patches, mucosa
Humoral vs cellular immunity
- Humoral - Ab mediated.
- Cellular - CTLs, NK, PMN, Macrophage,
- beta, gamma and delta compete to be the first to produce a productive form
- Beta has more chances because you only need the beta (as oppose to gamma AND delta) each chr has two chances to get a productive rearrangement
- If GD is made then it leave the thymus
- If B is made then there is a placeholder for A
- There is a another chance for DG to come up while A is tried out.
Positive vs negative selection
- Positive selection is first where weak binding abTCRs against MHCs are killed off while moderate and tight binding ones are promoted
- Negative selection is when moderate binding ones are promoted while tight binding ones are eliminated