Biomedical Engineering Reference
In-Depth Information
Tabl e 3. 1.
Blo
od cell approximated geometry and relative concentration.
Blood
Quantity
Relative
Size
Cell volume
(/mm
3
)
cell
proportion
(
m)
percentage
5
×
10
6
RBC
1
∼
8
97%
10
−
3
5
×
10
3
Leukocyte
∼
15
2%
3
×
10
5
6
×
10
−
2
Platelet
∼
3
1%
Hematopoietic stem cells, early progenitor cells, and precursor cells do not yet
express certain markers. The LSK (Lin
) phenotype defines a
primitive cell type that possesses self-renewal capacity, from which multipotential
cells MMP without self-renewal capacity develop.
Immunophenotyping consists in determining expression level of cell-surface
molecules on leukocytes. A molecule
−
,SCA1
+
,KIT
+
term (plus or minus symbol)
indicates whether a given molecule type is expressed or lacking on the plasma
membrane of a given leukocyte type. Some leukocyte types are also defined
as molecule
high
+
or molecule
−
(or molecule
bright
), molecule
mid
(or molecule
int
[intermediate]),
or molecule
low
(or molecule
dim
), according to the expression level, as well as
molecule
neg
/
low
molecule
mid
/
low
and
for
negative-to-low
and
medium-to-low
phenotypes.
In addition, cells can be characterized by intracellular markers such as certain
transcription factors as well as plasmalemmal markers only when they are activated
(molecule
act
).
3.2
Vasculature as an Immunity Compartment
The vasculature participates in the detection and protection against pathogens.
Blood vessels convey immunocytes to identify, prevent eventual dissemination of
invading bacteria to different organs, and eradicate these pathogens.
Intravascular motion of immunocytes, such as neutrophils, monocytes, and
invariant natural killer T cells, starts by transendothelial migration at target
sites. However, many bacterial products antagonize leukocyte recruitment, such
as lipopolysaccharide that can inhibit leukocyte displacement [
97
].
Endothelial cells contribute to innate immune responses to bacteria, as they
express Toll-like receptors, lymphocyte antigen Ly96 homolog,
1
and appropriate
adaptors [
97
]. Activated nuclear factor-
B primes synthesis of adhesion molecule
on endothelial cells that promotes neutrophil infiltration.
κ
1
A.k.a. MD2 and ESOP1 (ES-OP9 [coculture of embryonic stem cells and OP9 stromal cell line]
coculture clone-1). It is required for maximal responsiveness of TLR4 to bacterial lipopolysaccha-
rides. It enhances TLR4-dependent activation of NF
κ
B. It is secreted by many cell types such as
monocyte-derived dendritic cells.
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