Selectins

**Figure 3:** Schematic representation of the molecular structure of Selectins. On the amino terminal there is a Lectin like domain. There is also an epidermal growth factor like domain and 2-9 consesus repeats as are found in complement regulatory proteins.
$\begin{figure}\par\centering\par \includegraphics{selectin} \par\index{Selectin!Domains} \index{Selectin!Molecular structure}\par\end{figure}$

There are three members of the selectin family that participate in ``rolling''. These are P,E and L-selectin. They are expressed on the surface of leucocytes and activated endothelial cells. Selectins have a lectin domain on the amino (NH $_{2}$ ) terminal, an epidermal growth factor like domain and a series of two to nine short consensus repeats similar to complement regulatory proteins, see figure 3.

**Figure 4:** Schematic representation of life cycle of P-selectin. It is manufactured and stored in the Weibel-Palade body in endothelial cells (it is also found in $\alpha$ granules in platelets). Stimulation by hypoxia, free radicals, histamine and thrombin results in expression of P-selectin on the surface of the endothelial cell. The main ligand of P-selectin appears to be sialated Lewis on Leucocytes. It may also bind with L-selectin on leucocytes.
$\begin{figure}\par\centering\par \includegraphics{p-selectin} \par\index{P-selectin!Life cycle} \index{Weibel-Palade body}\par\end{figure}$