Page 1877 - Williams Hematology ( PDFDrive )

1852 Part XII: Hemostasis and Thrombosis Chapter 112: Platelet Morphology, Biochemistry, and Function 1853

rRNA-depleted preparation
12000
1N1
2N2 10847
3N3 10000
4N4 9597
9246
Number of platelet mRNAs
Average 8547
7993 8000
6000

4000

2000

0
5 0 –5 –10 –15 –20 –25
RNA-seq normalized reads, log ratios
2
Figure 112–8. Estimates of platelet expressed mRNAs. Platelet total RNA was extracted from four normal donors, depleted of ribosomal RNA (rRNA)
and subjected to RNA-seq. The number of platelet-expressed mRNAs (y axis) was plotted against RNA-seq read number in log2 ratios normalized to
β-actin. (Reproduced with permission from Bray, P.F., et al: The complex transcriptional landscape of the anucleate human platelet. BMC Genomics 16;14:1,
2013.)

a b
M 2
a b
L 2

a b
v 3

Figure 112–9. Platelet–leukocyte interactions. A number of interactions can occur between platelets and leukocytes, including neutrophils and
monocytes. The interaction between platelet P-selectin and leukocyte P-selectin glycoprotein ligand-1 (PSGL-1) probably is the most important initial
interaction (and can lead to tissue factor synthesis by monocytes), but fibrinogen binding simultaneously to activated α β on leukocytes and either
M 2
α β or α β on platelets may play a role under certain circumstances. Platelets can release platelet-activating factor (PAF), which can interact with a
V 3
IIb 3
PAF receptor (PAFR) on leukocytes, leading to α β activation and binding of fibrinogen and factor X. Leukocyte α β can also interact with platelet
M 2
M 2
junctional adhesion molecule-3 (JAM-3) or GPIb. Platelets can release chemokines (e.g., ENA-78, GRO-α, and RANTES [regulated upon activation,
normal T-cell expressed and secreted]), and β-thromboglobulin (βTG) released by platelets can be converted by leukocyte cathepsin G (CG) into the
potent chemotactic CXC chemokine NAP-2. Some of the chemokines, in turn, activate leukocytes by binding to the chemokine receptor CXCR2.
Platelets also contain the potent immune-stimulating molecule CD40 ligand (CD40L), and both express it on the platelet surface and release it into
the circulation upon platelet activation. The interaction between thrombospondin and CD36 molecules on both platelets and some leukocytes and
the presence of CD40 on platelets are not shown. VWF, von Willebrand factor.

Kaushansky_chapter 112_p1829-1914.indd 1852 17/09/15 3:27 pm