Introduction
The selectin family of adhesion receptors consists of three members: P-, E-, and L-selectin.
P-selectin is constitutively present in the α-granules of platelets and Weibel-Palade
bodies of endothelial cells and is rapidly translocated to the cell surface upon activation.
E-selectin is synthesized and expressed by activated endothelial cells, whereas L-selectin
is constitutively expressed by leukocytes. All three selectins support the rolling
of leukocytes on endothelium, which is a prerequisite to firm adhesion and extravasation
of leukocytes mediated by integrins and members of the immunoglobulin superfamily.1,2 More recently, it has been demonstrated that P- and E-selectin also support platelet
rolling in venules, which will be discussed below. In addition, P-selectin expressed
on the surface of activated platelets also mediates platelet-leukocyte adhesion.3,4
Since the discovery of the selectins, considerable efforts have been devoted to uncover
the functions of these molecules. The development of genetically engineered animals
deficient in one or more of the adhesion receptors has provided a unique opportunity
and an alternative approach to antibody-blocking experiments for defining the contribution
of each of the molecules in normal physiology and pathological conditions. At this
time, mice deficient in a single selectin, all combinations of two of the selectins,
and all three selectins have been produced by gene targeting.5-10 In this chapter, we will discuss some of the recent findings obtained using mice
deficient in P-selectin alone (P-/-), both P- and E-selectin (P/E-/-), and mice expressing
Pselectin with a deleted cytoplasmic domain (ΔCT).
