Lymphoid Flashcards
How do lymphoid stem cells turn in to Activated T and B cells?
- Pre-T/B cells formed in Thymus/bone marrow
- Naive B/T cell circulates
- Activated when it encounters an antigen
What is characteristic of the Thymus?
Septae and a clear medulla and cortex
What are the two cells types of the Thymic cortex?
- Thymocytes (T lymphoblasts)
- Thymic epithelial reticular cells (Antigen presenting cells, large euchromatic nuclei)
What are the three types of Thymic epithelial cells?
1-Squamous TECs forming a layer connected by desmosomes (blood thymus barrier)
2-Stellate TECs, cytokine secreting Antigen presenting cells
3-Squamous TECs expressing MHC II and form corticomedullary barrier
What three types of TECs are in the Medulla?
1-Second layer of squamous TEC forming corticomedullary barrier
2-cytoreticulum to support T cells (expression of proteins from other organs)
3-Aggregates forming Hassall corpuscles
The entry and exit point where diapedesis takes place in the thymus is called what?
High endothelial venule (make of cuboidal epithelium)
Positive selection happens where and selects for what?
happens in cortex, selects for things that recognize self
Negative selection happens where and selects for what?
happens in the medulla, selects against things that strongly recognize self
Areas staffed by T cells are called what?
Thymus -dependent
Lymph nodes resemble what other organ as far as their general structure?
Kidney
What are the three regions of lymph nodes?
Cortex
Paracortex
Medulla
What space is found between the cortex and the capsule?
subcapsular sinus (receives lymph from afferent lymphatics)
What cell is most present in the paracortex?
T cells
What are the two main structures found in the medulla or lymph nodes?
- medullary cords (cord-like masses of lymphocytes extending from paracortex, plasma cells)
- Medullary sinuses (discontinuous endothelium separating cords, contain macrophages and PMNs)
Reactions in the node activate the __________ handshake. Activated T cells activate the _________ handshake causing plasma cells to secrete antibodies.
1st, 2nd
Where does isotype switching take place?
germinal centers in secondary nodules
Which antibodies are first to be produced?
IgM
Which antibodies are associated with secretions?
IgA
Which antibodies are most abundant and are important for long term resistance as well as crossing the placenta?
IgG
Which antibodies are associate with mast cells and basophils. Contribute to allergic response and parasite killing?
IgE
What do Tc cells do?
Scan all cells in the body through circulating
What attracts lymphocytes to specific nodes?
homing receptors and cytokines
Dry nodes produce?
IgG
Wet nodes produce?
IgA
Pain associated with a swollen node is caused by what?
Cytokines
*no pain associated with swelling may be signs of lymphoma
What are the two main things the Spleen does?
- filter blood
- turnover old blood cells
What are the two regions of the spleen?
Red pulp (blood turnover) white pulp (aggregations of lymphocytes)
*marginal zone found between these two
What surrounds central arteries in the spleen?
T cell sheath called PALS (periarterial lymphatic sheath)
Removing an entire old blood cells is called?
culling
-macrophages engulf them
Removing an inclusion of an RBC is called?
Pitting
-Macrophage just engulfs the nuclear fragment or parasite
A B cell response in the spleen causes the central artery to be?
Eccentric
*T cell expansion tends to be more uniform
Large collections of lymphocytes containing mostly B cells with some helper T cells (CD4) such as in tonsils, peyers patches and the appendix are called what?
MALT (mucosa-associated lymphatic tissue)
What is characteristic of the palatine tonsil?
Crypts and SSQE
