chapter 4 - microenvironment

Question 1

why are microenvironments important?

Answer 1

because they allow for cells and organs that are highly organized to interact

Question 2

what is a Stem cells Niche?

Answer 2

supportive network of stromal cells in the bone marrow

Question 3

what is the major site for hematopoiesis in adults?

Answer 3

bone marrow of large bones

Question 4

what is the major site for hematopoiesis in a fetus?

Answer 4

Yolk sac, aorta-gonad-mesonephros(AGM) region, placenta, liver

Question 5

Stromal cells provide ____ for HSC ___ and ____

Answer 5

support, growth, development

Question 6

Stromal cells and their functions:
Osteoblasts
Endothelial cells
Reticular cells
Sympathetic cells
Adipocytes

Answer 6

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?

Question 7

HSC move from ___ to ___ as they mature

Answer 7

endosteal niche to the vascular niche

Question 8

between what structures can mature myeloid and lymphoid cells circulate?

Answer 8

between the bone marrow and the secondary organs

Question 9

where do T cells migrate to mature?

Answer 9

thymus

hence why it’s largest at puberty

Question 10

what are some important cells for thymocyte development

Answer 10

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

Question 11

cortical thymic epithelial cells (cTEC) function

Answer 11

allow for positive selction so that T cells can interact

Question 12

medullary thymic epithelial cells (mTEC)

Answer 12

allow for negative selction so T cells don’t interact with self

Question 13

where do B cells mature?

Answer 13

thymus

Question 14

how do immune cells interact with pathogens and become activatexd?

Answer 14

1. leukocytes move to site of infection from circulation
2. specialized organs trap antigens (spleen, lymph nodes, peyer’s patches)

Question 15

how are lyhphoid organs connected to the lyphatic sytem?

Answer 15

via ducts and nodes

Question 16

how does lymph move?

Answer 16

by movement of surrounding muscles

Question 17

lymph nodes trap what kind of antigen?

Answer 17

tissue born antigen

Question 18

spleen traps what kind fo antigen?

Answer 18

blood-born antigens

Question 19

what is the lymph node?

Answer 19

a highly organised struture
B cells and T cells zones
the follicular dendritic cells maintiant he follicular and genminal centers

Question 20

explain the antigen’s experience

Answer 20

1. Ag enters via the afferenent lympthics
2. empties into the subcapsular sinus
3. trapped by the APC, either migrating through the LN or residence

Question 21

explain the T cell’s experince

Answer 21

4. naive T cells enter the LN through the high endotheilal venules (HEV)
5. Spend 16 to 24 hours in the LN browsing for the antigen on the APC
6. 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)

Question 22

what’s happening in the paracortex (T cell zone) ?

Answer 22

the fibroblast/follicular reticular cells(FRC) create processees and conduits to allow T cells to interact with the APC

Question 23

what is the B cell experinec?

Answer 23

4. enter the LN via the HEV
5. migrate through the paracortex into the follicles
6. a) leave via efferent lympatics if no match Ag

b)if they encounter an Ag mathc they become actiavted and internalize it

7. moves to the paracortex to allow full actiavtion by interacting with the T cell
8. some B cells re-enetr the follicule and establish the germinal center (aka secodnary follicle)
9. some B cells become plasma cells, reside in the GC or in the bone marrow

Question 24

how long does it take to establish a GC? how long does it take for a GC to be active?

Answer 24

4-7 days (LN swell)
3 weeks

Question 25

what is something the follicular dendritic cells do for B cells

Answer 25

they provide support for B cells to encounter Ag

Question 26

What are the parts of spleen to know?

Answer 26

red pulp
white pulp
follicle

Question 27

what is the red pulp and white pulp of the spleen separated by?

Answer 27

marginal zone

Question 28

what is the red pulp?

Answer 28

old red blodd cells are removed

Question 29

what is the white pulp?

Answer 29

lymphoid -rich region

with the PALS (periarteriolar lymphoid sheeath)
with the T cells and B cells follicles and GC

Question 30

How does Ag enter the splen and leave the spleen?

Answer 30

enters via the splenic artery and exits via the splenic viein

once it enter it encounter the DC marghinal zone whihc traps and processes it. DC migrates to the PALS and activates T cells and Bcells

Question 31

what are MALT regions?

Answer 31

Mucosal-associted lymphoid tissue

Question 32

what are Peyer’s patches

Answer 32

they trap intestinal antigens

Question 33

helathy mucose is smooth or bumpuy

Answer 33

bumpy

Question 34

talk about T cell and B cells as memory cells

Answer 34

• resideu in secodnary lynphoid organs or BM (b cells) - central memory cells
• can residue to the tissues that originall encountered Ag - tertiary lymphoid tissue
• microenvironments, stroma

effector cells resdiue in tissue

Question 35

what are the tissue residue macrophages?

Answer 35

langerhans cells