Organs of Immunity Flashcards
Bone Marrow/Bursa of Fabricus
Primary and secondary lymphoid organ
Site of early lymphocyte development in mammals (marrow) and birds (bursa)
T cells then migrate to thymus
B cell receptor arrangement is in marrow/bursa
Also act as secondary lymphoid organs
Site of hematopoiesis, and where B cells reside
Stromal cells support lymphopoiesis and myelopoiesis via both surface ligands and secretion of certain cytokines/growth factors
cytokines (e.g. IL-7) produced in peripheral tissues circulate to marrow and influence proportion of cell types produced
B cells differentiate in compartmentalized follicles/vacuoles. They move to the center as they differentiate and then move out
Thymus
Primary and secondary lymphoid organ
Naive/immature T cells leave marrow, migrate to thymus to complete maturation
In upper anterior thorax of most spp., but vary in size and shape
consists of lobules of loosely packed epithelial cells, presentation of self Ag only, involutes after sexual maturity
Hassall’s corpuscle - concentric epithelial cells - role in tolerance
Cortex - densely packed with immature T cells
Medulla - less dense collection of mature lymphocytes
Peyer’s Patches
Primary and secondary lymphoid organ
structures located along the GI tracts w/in lamina propria (line the gut)
contain large numbers of (mostly) B cells
arranged in follicles w/B cells central and T cells surrounding them
Important for IRs (or lack thereof) for ingested Ag
Germinal center = site where B cells are rapidly dividing
Peyer’s patches take up Ag from the gut and transport it to draining lymph nodes
Tonsils
secondary lymphoid organ
Spleen
Secondary lymphoid organ
If excessive blood cell production is demanded, liver and spleen can serve as sites for lymphocyte production
compartmentalized structure encased in thick capsule
Red pulp contains phagocytes
White pulp contains lymphocytes (mostly B, some T) = all lymphocytes, collectively arranged along blood vessels (also plasma cells and MPs, IRs)
White pulp has 2 components: splenic nodules (lymph nodules) - contain B lymphocytes; and periarterial lymphatic sheaths - T cells
Largest lymphoid organ
major site of adaptive IRs to blood-born pathogens
Filters out effete RBCs
RBCs are also stored here
Lymph Nodes
Most important secondary lymphoid organ
encapsulated; located thruout body
Points of convergence for cells in blood and lymph systems
Collects EC fluid (lymph) from tissues for return to blood)
contain B and T cells in segregated regions
Bean-shaped; divided into cortex, medulla (surrounded by capsule)
vessels enter or leave via the hilus
lymphocytes can enter via blood (high endothelial venules)
DCs can enter via afferent lymphatics
See lymph node drawing and be able to draw and label it!
Primary Lymphoid Tissues
Lymphocytes are produced, develop & differentiate
Stromal fibroblasts and fat cells interact w/precursors to stim. development
Bone marrow/bursa of Fabricus, Thymus, Peyer’s Patches
Secondary Lymphoid Tissues
Lymphocytes contact, collect, and respond to specific Ags (lymphocyte activation
Tonsils, spleen, lymph nodes, Peyer’s patches, bone marrow
