chapter 4 - microenvironment Flashcards
why are microenvironments important?
because they allow for cells and organs that are highly organized to interact
what is a Stem cells Niche?
supportive network of stromal cells in the bone marrow
what is the major site for hematopoiesis in adults?
bone marrow of large bones
what is the major site for hematopoiesis in a fetus?
Yolk sac, aorta-gonad-mesonephros(AGM) region, placenta, liver
Stromal cells provide ____ for HSC ___ and ____
support, growth, development
Stromal cells and their functions:
Osteoblasts
Endothelial cells
Reticular cells
Sympathetic cells
Adipocytes
Osteoblasts - generate bone and control HSC differentiation
Endothelial cells - line the blood vessel and regualte HSC
Reticular cells - connect bone to blood vessels via long processes (arms)
Sympathetic cells - can control the release of HSC from the bone marrow
Adipocytes - regulatory? Space -filling?
HSC move from ___ to ___ as they mature
endosteal niche to the vascular niche
between what structures can mature myeloid and lymphoid cells circulate?
between the bone marrow and the secondary organs
where do T cells migrate to mature?
thymus
hence why it’s largest at puberty
what are some important cells for thymocyte development
cortical thymic epithelial cells (cTEC)
-allow for positive selection, select for T cells that can interact
medullary thymic epithelial cells(mTEC)
- enable negative selction, remove t cell that interact with self antigens
cortical thymic epithelial cells (cTEC) function
allow for positive selction so that T cells can interact
medullary thymic epithelial cells (mTEC)
allow for negative selction so T cells don’t interact with self
where do B cells mature?
thymus
how do immune cells interact with pathogens and become activatexd?
- leukocytes move to site of infection from circulation
- specialized organs trap antigens (spleen, lymph nodes, peyer’s patches)
how are lyhphoid organs connected to the lyphatic sytem?
via ducts and nodes
how does lymph move?
by movement of surrounding muscles
lymph nodes trap what kind of antigen?
tissue born antigen
spleen traps what kind fo antigen?
blood-born antigens
what is the lymph node?
a highly organised struture
B cells and T cells zones
the follicular dendritic cells maintiant he follicular and genminal centers
explain the antigen’s experience
- Ag enters via the afferenent lympthics
- empties into the subcapsular sinus
- trapped by the APC, either migrating through the LN or residence
explain the T cell’s experince
- naive T cells enter the LN through the high endotheilal venules (HEV)
- Spend 16 to 24 hours in the LN browsing for the antigen on the APC
- a) leave via efferent lymphatics if don’t find Ag match
b)if find they find an Ag match they will stay in the node where it proliferates and differentitaes into effector cells(kill or direct the killing)
what’s happening in the paracortex (T cell zone) ?
the fibroblast/follicular reticular cells(FRC) create processees and conduits to allow T cells to interact with the APC
what is the B cell experinec?
- enter the LN via the HEV
- migrate through the paracortex into the follicles
- a) leave via efferent lympatics if no match Ag
b)if they encounter an Ag mathc they become actiavted and internalize it
- moves to the paracortex to allow full actiavtion by interacting with the T cell
- some B cells re-enetr the follicule and establish the germinal center (aka secodnary follicle)
- some B cells become plasma cells, reside in the GC or in the bone marrow
how long does it take to establish a GC? how long does it take for a GC to be active?
4-7 days (LN swell)
3 weeks
