Blood Cells - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 60

Members of the NLRP (NOD-like receptor [NLR] pyrin domain-containing)
subfamily of the NLR family of cytoplasmic receptors of the innate immunity
sense various pathogenic and chemical agents and trigger the formation of in-
flammasomes. These NLRP scaffolds can bind adaptor and signaling proteins,
such as apoptosis-associated speck-like protein containing a CARD (ASC), HSP90,
suppressor of G2 allele of S-phase kinase-associated protein SKP1 (SuGT1), and
caspase-5 [ 99 ]. The procaspase-1-NLRP1-ASC complex releases active caspase-1
that cleaves precursors of IL1 and IL18 interleukins.

Membrane-associated guanylate kinases (MAGuK) constitute a family of
scaffolds that include Disc large homologs (DLg1-DLg4), 14 zona occludens-1,
CARMA (N-terminal caspase activation and recruitment domain [CARD]-
MAGuK-like domain-containing), and MAGI1 (MAGuK-like, WW, and PDZ
domain-containing with inverted domain organization protein-1) [ 99 ]. Scaffold
spinophilin, more precisely PP1 r9 regulatory subunit (inhibitor) of PP1
phosphatase, 15 is involved in dendritic cell functioning, as it can act in the formation
of immunological synapses.

β

3.5 Red Blood Capsules

In the present textbook, erythrocyte, or red blood cell (RBC), is called red blood
capsule, because it defines a hemoglobin (Hb) solution 16 bounded by a thin flexible
membrane (non-nucleated cell).
In its undeformed state, it has a biconcave disc shape with a greater thick-
ness in its outer ring (diameter 7

. 7 ± 0 . 7 m, central and peripheral thicknesses

m 2 , volume 1 . 4 ± 0 . 5 mand2 . 8 ± 0 . 5 m, aspect ratio ∼ 0.4, surface ∼ 140

m). It can then deform 17 with a negligible
bending resistance, in particular with a parachute shape when moving through
tiny capillaries. Its mass density is equal to about 1100 kg/m 3 . It lives an average
of 120 days. The RBC number is age- and sex-dependent (4.2-5.5

m 3 , membrane thickness

∼ 90 ∼ 0.02

10 6 /mm 3 × in

10 6 /mm 3 in men). women, and 4.5-6.2 ×

3.5.1 Formation, Maturation, and Clearance

In adults, definitive erythropoiesis occurs in the bone marrow. Erythroblasts are
associated with macrophages in anatomical units ( blood islands ). Nuclei are

14 Four genes in mammals encode DLg1 to DLg4 that are also called SAP97, PSD93, SAP102, and
PSD95, respectively. Scaffold DLg1 that is recruited to the immunological synapse binds TCR,
P38MAPK, and other scaffolds.
15 Spinophilins are encoded by the PPP1R9A and PPP1R9B genes in humans.
16 The kinematic viscosity (

ν ) of the Hb solution is greater than that of water ( ν ∼ 6mPas) [ 101 ].

17 RBC deformability can be estimated by transit time during filtration.