Functional Lymphoid Anatomy Flashcards
What is central lymphoid tissue?
Bone Marrow
Thymus
What is peripheral lymphoid tissue?
Spleen
Lymph Nodes
What is the function of central lymphoid tissue?
- Responsible for lymphopoiesis
* Responsible for central tolerance
What is the function of peripheral lymphoid tissue?
- Mixture of B & T cells
- Supports circulating lymphocyte survival
- Activation of naïve lymphocytes
- Peripheral tolerance
What is the function of the bone marrow?
All lymphocytes develop from HSCs in the bone marrow
What factors does B cell development depend on?
Progression of B cell development depends on factors made by stromal cells:
- IL-7
- FLT3 Ligand
- SCF (stem cell factor)
- CXCL12
Where do the B cells move as the mature in the bone marrow?
They move toward the central sinus of the
marrow cavity, then into circulation, bound for the peripheral lymphoid organs
How does central tolerance play a role in B cell development?
Self-reactive B cells will die by apoptosis.
Soluble self with cross linking self molecules
are made anergic but do go to the periphery
What is found in the thymic cortex?
Cortex: contains only immature thymocytes & scattered macrophages
What is found in the thymic medulla?
Medulla: more mature thymocytes, dendritic cells & macrophages
What role does central tolerance play in T cells?
T cells will recognize Ag-MHC but only become activated when the Ag is NOT self
What attracts lymphocytes into the paracortical area of lymph nodes?
Chemokines
What occurs in the outer cortex/subcapsular area of the thymus?
Double negative (CD3+) cells are formed
What occurs in the deep cortex of the thymus?
Immature double positive cells are formed
What occurs in the medulla of the thymus?
Positive selection of the DP cells and negative selection of the SP cells that will generate cells with central tolerance.
