Blood Cells - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 89

3.6.7 Inflammatory Platelet

Platelets can also be considered as inflammatory cells that synthesize proteins in-
volved in inflammatory pathways (Chap. 11 ). Granules

of platelets indeed contain
inflammatory modulators, such as P-selectin, 63 tumor-necrosis factor superfamily
member TNFSF5, 64 thrombospondin-1, CXCL4 chemokine, 65 transforming growth
factor-

α

β , and interleukin-1 precursors.

3.7 Granulocytes

Granulocytes are innate immunocytes that contain granules involved in immune
defense. They are also called polymorphonuclear leukocytes, as their nuclei are
usually lobed (2-4 lobes). The names of the 3 types of granulocytes are derived
from neutrally, eosinophilic, and basophilic staining of cytoplasmic granules.

3.7.1 Basophils

dm 3 ) have numerous large basophilic
granules. They represent less than 1% of all leukocytes. Basophils are the least
abundant granulocytes. These short-lived cells have an expected half-life of a few
days. Basophils express immunoglobulin-E receptors (Fc

Basophils (B ϕ ; size 12-15 m; 20-80

R1).

high , 66

hema-
topoietic progenitors in the bone marrow that express transcription factors CCAAT-
enhancer-binding protein-

Circulating basophils originate from CD34 + ,Fc R1 α SCFR −

α and GATA2 [ 173 ]. Mature basophils exit the bone

marrow.
Activated T lymphocytes produce interleukin-3 and other factors to enhance
basophil production in the bone marrow. Because Fc R1 expression can change

during immune response, PTPRc (or CD45) is a useful marker of basophils. 67

63 P-selectin leads to aggregates of activated platelets and leukocytes.
64 Cytokine TNFSF5 allows platelets to bind to macrophages, T lymphocytes, and endothelial cells,
as well as to other platelets via 3 -integrin. It also activates an inflammatory cascade involving

E-selectin, VCAM, and ICAM1 for leukocyte adhesion.
65 A.k.a. platelet factor-4.
66 Subunit of the tri- or tetrameric, high-affinity IgE receptor encoded by the FCER1A gene.
67 Unlike other myeloid lineage cells that are CD45 high , in which high-molecular weight forms
(CD45 hMW ) are, after activation, gradually replaced by low-molecular weight forms (CD45 lMW ),
basophils are CD45 mid

α β 2B

[ 173 ].