Lecture 14 - Functional Lymphoid Anatomy - FINAL Flashcards
What are the 7 important lymphoid tissues?
- Adenoid
- Tonsils
- Lymph Node
- Spleen
- Peyer’s Patch in Gut
- Bone Marrow
- Thymus
What are the 4 purposes of lymphoid tissues?
- Supports lymphopoiesis
- Supports development of incredibly diverse repertoire of antigen-specific lymphocytes
- Critically important for both central & peripheral tolerance
- Provides sustaining signals for lymphocyte survival
Which of the following are central lymphoid and which are peripheral lymphoid tissues?
- Lymph node
- Thymus
- Spleen
- Mucosal
- Bone marrow
Bone Marrow & Thymus = central
the rest are peripheral
Which lymphoid tissue (central or peripheral)
Are responsible for the following:
- Lymphopoiesis
- Central Tolerance
- B cells
- T cells
CENTRAL
B cells - continually made from bone marrow
T cells migrate to the thymus during embryogenesis to develop there
What are the main functions of the peripheral lymphoid tissues?
- Mixture of B and T cells
- Supports circulating lymphocyte survival
- Activation of naïve lymphocytes
- Peripheral Tolerance
- catches any lymphocytes that are auto reactive that may have escaped central tolerance
All lymphocytes develop from HSC in the ______.
T-cell progenitors migrate to the _____.
B-cells develop in the bone marrow
_______ in the bone marrow, are critically important to B cell development
- Bone Marrow
- Thymus
- Bone marorw
- STROMAL CELLS
What are some areas besides the bone marrow where B cells develop?
- Fetal Liver
2. Neonatal spleen
Early stem cells hand out where? Where do they move after this?
Progression of B cell development depends on maturation factors provided by the stream cells. Name some examples
Early stem cells hang out at the endosteum, just below the inner cavity of the long bones, but then move toward the stromal cells in the trabeculae
- such as FLT3 ligand,
IL-7
Stem-Cell Factor (SCF)
CXCL12
As B cells mature they move toward the _____ of the marrow cavity and then into the circulation, heading for what organs?
- CENTRAL SINUS
2. Peripheral Lymphoid organs
Central tolerance is what?
What happens if an immature B cells meets its antigenic match in the peripheral lymphoid organs?
Self-reactive B cells die by apoptosis prior to leaving the bone marrow (central tolerance)
- it will mature into antibody producing plasma cells & memory B cells
What are the 2 most important PERIPHERAL ONLY lymphoid structures?
- Lymphoid follicles
2. Germinal Center
_____ contains only immature thymocytes & scattered macrophages
_____ more mature thymocytes, dendritic cells & macrophages
Mice & Children without thymus do not what?
CORTEX
THYMUS
NO THYMUS = NO T CELLS despite lymphoid progenitors
What do thymocytes depend on for survival? Which cytokine?
- Thymic Epithelial Cells
2. IL- 7
When is the rate of T cell production greatest?
When does it begin to shrink?
- Before puberty
- Begins to shrink after puberty
- the production of new T cells is lower but not entirely absent
Early on, thymocytes have no surface markers, including the T-cell receptor _____
CD3
Further interaction with thymic stromal cells give rise to “double negative” cells, that are (+) for CD3, but lack the _______
co-receptors CD4 or CD8
When does the beta chain of the TCR rearrange?
When does the alpha chain rearrange?
Double Negative phase
When the cell is a DOUBLE POSITIVE
T cell central tolerance:
Which cells undergo positive selection?
Negative Selection?
- DP cells with low affinity for peptide MHC complex will SURVIVE as ISP
- Single Positive thymocytes that have high affinity for peptide - MHC will be deleted
True or false:Thymic cortical epithelial cells express self peptide in MHC I or MHC II molecules
TRUE
ANtigens in the lymph notes freely float or are actively brought by APC’s to the node via ____
CHEMOKINES
-They are brought to the lymph node by the afferent lymphatics into the paracortical areas
Chemokines also bring in circulating lymphocytes from the blood toward the paracortical area
Lymphocytes squeeze out of the vessels through _________ into the paracortical areas
High Endothelial Venues
What are 2 ways lymphocytes can be activated in the lymph node?
- Antigen can be brought displayed in MHC of APCs & presented to T-cells
- Free antigen can also be captured by LN macrophages & presented directly to follicular B cells, to paracortical T cells & passed to follicular dendritic cells.
When they become activated, T cells and B cells both move to the border of the ____ and T-cell zone, & T cells can provide their helper function to B cells
Follicle
What are the 3 main functions of the spleen?
What is it especially good at doing?
- Immune responses to blood-borne pathogens (white pulp)
- RBC Disposal & Iron recycling (red pulp)
- Secondary Hematopoiesis (if needed)
- Especially good at clearing infections with encapsulated bacteria
Pneumococci Meningococci
