BIOL 435 Ch. 2 Part Two (Cells and Organs of the Immune System) Flashcards
during embryogenesis and the fetal period
- blood cell formation shifts from site to site
- bone marrow hasn’t arisen yet
steps in ‘blood cell’ formation
- hematopoiesis begins the yolk sac
- fetal HSCs arise near the kidney
- mature HSCs capable of populating the hematopoietic system can be isolated from yolk sac, placenta, and fetal liver
- HSCs seed the bone marrow late in fetal development
- HSCs ultimately populate the bone marrow postnatally
by 18years of age (bone marrow sites)
- vertebrae
- ribs
- sternum
- skull
- pelvis
- humerus
- femur
primary lymphoid organs
- Bone marrow
- Thymus
* where immune cells develop
bone marrow has
- B-cells
- monocytes
- dendriteic cells
- granulocytes
HSCs reside (bone marrow)
- in the perivascular niche
- develop in contact with the stromal cells of the bone marrow
perivascular niche
- directs the development of blood cells
- HSCs
- marcrophages
- blood vessel
- cytokines and GFs
- sympathetic neuron
endosteal niche
-osteoblasts
>generate bone
>regulate differentiation of lymphoid cells
stromal cells facilitate
- HSC proliferation
- direct migration
- stimulate differentiation
stromal cells include
- endothelail cells: lining blood vessels
- sympathetic nerves
- macrophages
- osteoblasts
T and B cell maturity
- T-cells leave bone marrow immature and mature in thymus
- B-cells mature more in bone marrow but still not fully
stepwise changes in thymocytes (T-cells)
- due to microenvironment of the thymic cortex and medulla
1. Immature T-cells enter at CMJ
2. DN
3. DP
4. SP
CMJ
- cortico-medullary junction
- where immature T-cells enter
DN
- double negative T-cell
- no CD4 or CD8
- TCR expressed
DP
- double positive T-cell
- CD4 and CD8
thyme epithelial cells (TEC)
-coritcal and medulluary
-95% of T-cells ‘die’ (don’t recognize MHC)
-other 5% undergo postive and negative selection
>need to recognize MHC, just the right amount
positive and negative selection
-driven by TCR affinity of binding with MHC-peptides
secondary lymphoid organs
-areas where lymphocytes: >encounter antigens >become activated >undergo clonal expression >differentiate into effector cells
secondary lymphoid organ areas include
- lymph nodes
- spleen: blood
- mucosa-associated lymphoid tissue (MALT)
- other diffuse and loosely organized areas
- connected to each other via blood and lymphatic circulatory systems
lymph nodes and spleen
-most highly organized secondary lymphoid organs
in lymph node
-lymphocyte activity is seperated into distinct microenvironments
>cortex (B-cells)
>paracortex (T-cells)
innermost lymph node medulla
- macrophages and dendritic cells
- also get B-cells that become plasma cells
antigens enter via
-afferent vessel
exit via effernt vessel
-lymphocytes
naive lymphocytes enter by
-high endothelial venule (HEV)
3 roughly concentric regions of lymph nodes
- Cortex
- Paracortex
- Medulla
cortex (lymph nodes)
- lymphocytes
- macrophages
- follicular dendritic cells arranged in follicles
paracortex (lymph nodes)
- T-cells
- migrating dendritic cells
medulla
- site of lymphocyte egress
- plasma cells secreting Ab
follicle (B-cell zone)
-when activated move to cortex and can activate T-cells
>both cells work together
germinal centre
-explosion of B-cell differentiation
>why lymph nodes swell
lymphoid cells actively migrate
-toward each other during activation events for their required interactions
lymphoid FRCC
- lymphoid fibroblastic reticular cell conduit
- guides T-cells and APCs toward activation interactions
differentiation into effector cells
-takes place in follicles of secondary lymphoid organs
>both B and T-lymphocytes will develop into long-lived memory cells
CD4+ T-cells differentiate
-into helper T-cells that assist in B-cell differentiation
CD8+ T-cells differentiation
-into killer (or cytotoxic) T-cells that destory virally infected cells
spleen is the first line of defense
- against bloodborne pathogens
- Ag+lymphoctyes in through splenic artery and out throug splenic vein
spleen divided into lobes
-each contain red pulp, white pulp seperated by a marginal zone
>RBCs: red pulp
>WBCs: white pulp
>marginal zone
marginal zone
- a specialized region of macrophages and B-cells
- borders the white pulp
MALT
- loosely associated
- mucoas-associated lymphoid tissue
- important layer of defense against infection at mucosal and epitheial layers
- organizes responses to antigens taht enter mucosal tissues
ex. GALT, SALT, BALT
GALT
- gut-associated lymphoid tissues
- includes a network of follicles and lymphoid microenvironments assocaited with the intestines
M-cells
-responsbile for transcytosis
