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
Negative selection
If the single-positive cell recognizes the self-MHC:self-antigen complex too strongly, then it will be killed. If not, it can migrate out of the medulla and into the periphery
Peripheral lymphoid tissues
Aggregations of lymphocytes in non-leukocytic stromal cells that give out survival signals
Basic principles of peripheral lymph tissues
Trap the APCs and antigens in the same area as the lymphocytes so a secondary response can be elicited
Keep the lymphocytes that didn’t encounter their antigen alive so they can recirculate
What mediates the homing of lymphocytes
Chemokines
How long does it take for the adaptive immune system’s effects to be seen?
1 week
Steady state
When naive lymphocytes don’t meet their match, they will recirculate until they do find their match or they die
High endothelial venules
In the paracortical areas; how the naive lymphocytes get into the lymph node
Follicles of lymph node
Where B cells are located in a lymph node
Cortical area of lymph node
Outer portion of the lymph node, where the follicles are
Paracortical area of lymph node
Deep cortex where T lymphocytes are
Passage of lymphocytes through the spleen
Enter in the marginal sinus of the red pulp, leave through the white pulp
PALS
Periarteriolar lymphoid sheath; mainly T cells
Follicles of the spleen
Next to the PALS; could be germinal centers,
Marginal zone of the spleen
Surrounds follicle; contains macrophages and resident, non-circulating B cells
GALT
Collect antigen from the endothelial gut tract
Microfold cells
Directly collects antigen from the lumen
B cells in the gut produce what antibodies?
IgM, but mostly IgA
BALT
In the bronchus/airway
What enzymes and antibodies are produced by BALT?
Defensin, IgM, IgA, IgG
