Functional lymphoid anatomy Flashcards
Stromal cells
Provide signals that direct the development of progenitor cells and eventually B cells
Where do the final stages of B cell development occur?
In the periphery
Central tolerance
Immature B cells are tested in the bone marrow to test for self-reactivity
Course of B cells out of the bone marrow
Leave via sinusoids that enter the central sinus and are carried by veins to the spleen
Where/when do T cells develop?
In the thymus; migrate there as progenitor cells during embryogenesis
How are T cell numbers maintained?
Through long-lived T cells and division of mature T cells outside the central lymphoid organs
Thymic cortex
On the outside of the thymus; only contains immature T cells and most maturation happens here
Corticomedullary junction
Where T cell progenitors enter
Thymic medulla
Inner region where more mature single-positive T cells, as well as macrophages and dendritic cells
Thymic cortical stroma
Network of epithelium where the developing T cells reside; they have both MHCI and MHCII on them
Double-negative cells
The first portion of T cells have no CD3 or CD4/8 expression
Double-positive cells
As the T cells continue to move toward the medulla, they undergo receptor rearrangement until they are positive on all three
What happens if the double-positive cell does not recognize self-peptide:self-MHC?
They undergo apoptosis
What percentage of T cells die in the thymus?
98%
Positive selection
If the double-positive cell can recognize the self-peptide:self-MHC complex, then it will survive, drop a positive, and become either CD3+CD8+ or CD3+CD4+ and migrate to the medulla
