Primary and secondary lymphoid organs Flashcards
where does Sequential rearrnagement of antigne receprot genes take place?
BM ( B cells) or thymus (T cells)
Describe the development of B cells in the bone marrow
- rearrnagement of heavy and heavy chaisn to get functioanl BCR membrna ebound IgM or igD
- leaves the BM are mature but naiev B cells
- mature B cells leave the bone marrow
- migrate to secondary lymphoid tissues (spleen lymnodes)
- to mature further- vai T cell dependent or idnependnet way
what is the role of bone marro stromal cells
provide sutibale microenviroment for B ceel developmetn
without cannot have functional gene rearrrangemtn for BCR
release cytoine IL-7- esswntial.
describe a otherview of T cell development?
HSc—> T cell lineage in BM
migrate to thymus
Development of TCR( functioanl geen rearrangment)
+/- selection
Describe the Thymus
multi lobed organ
outer capsule- fiborus protection
2 distincit inner layersouter cortex, inner medulla (each ahs role in T cell maturation
Hassalls corpuscle
what happens to the thymus with age?
sequesters with age- T cell response diminished- may lead to increase infections in elderly
where are Hassalis corpuscle found and what can we use them to identify/ purpose
found in the thymus Medulla
idnetify thumus in histology
instruct dendritic cells to induce Cd4+ CD25+ regualtory T cells in human. Potent source of TSLP
what is this the Histology of?
The thymus
Describe T cell development in adult
Progenitor T cell form BM
double negativ ethrymocytes (CD4-,CD- also TCR-)
T cell preucors enters subcapsular cortical areas
encounter netowrk of cortical eptihelail celsls (thymic stroam IL-7 again)
cortex- double negative cells, functional rearranagement of A and B TCr chains- then express Cd4 or Cd8. then negative selection
Medulla- positive selection, become single positive (cd4 or Cd8)
what happens to the thymus output with age?
sequesters with age
less robust reposne to novel infections- fall in thymic ouput
number of memory T cells maintained
number of new naive T cells we produce decreases over time
increase in ifnections with age, dififuclty with new infections
describe the Secondayr lymphoid organs
main sites of immune acitvation against anrtigen ( T cell dependent)
spleen also importnatn in B cell developement
follicular B cells
MZ B cells
what is the function/structure of lymph nodes
main drianage/filter for lymoph for antigens from peripheral tissues ( free soluble antigens and on AP follcilualr denritic cells)
highly vacualrised
in tact with lymph and blood supply
have follicles which may contain germianl centres
(MZ = mantle zone, possibel population of T cells and unactivate dB cells), Germinal centres= B cells
what is this histology of
GC- germinal centre B cells, within a follicle
MZ- T cells
in the lymph node where are B and T cells mainly found?
B cell- in the follciles
T cells in the paracortex
in the Lymph node paracortex- whare are the high endothelial venules purpose? (HEV)
Allow T cells to enter directly from the blood into the lymph node paracortex ( also enter via a fferent lymphatic vessels)
can be recognsied by cuboaidal epithelials clles
in T cell dominant immunological response may obsevre expansion of the paracortical region
describe the histology of the spleen?
red and whit epulp mixed together
Trabecula- conective tissue around the spleen - supprots spleen and carries blood vessles
what type of lymphocytes might you see in the periarteriolar lymphoid sheath
T cell rich zone
where do the lymph nodes and spleen individually pick up infections
Lymph nodes- peripheral tissiues
spllen- in the blood
what is this the hisotlogy of?
tonsils- Malt tissues
Muscoal associated lymhpoid tissues
encpasulated
two palatine, 1 lingual, 2 tubula 1 adneoid
what are payers pathces
example of diffuse malt/ GALT
commonly found in the ileum
lies right beneatht the mucosal layer
cotnain M cells- specialsiezed eptihelial cells that reside abov peyers patches to take up antigens (have germianl centres)
