ABSTRACT

In this chapter we will focus on the development of the lymph node vasculature. In lymph nodes one can find arterioles, capillaries, and venules. It is at a particular site, immediately after the capillary network, that lymphocytes are able to leave the bloodstream and transmigrate into the underlying tissue. The endothelial cells involved in this process are highly specialized: they constitutively express a variety of adhesion molecules necessary to slow down and bind the passing lymphocytes. In addition, the endothelial cells are likely to produce chemokines that trigger the lymphocytes in the bloodstream. Morphologically, these endothelial cells are easily distinguishable since they have a high, cuboidal appearance. The intruiging function of these endothelial cells has triggered many researchers to study these cells in more detail. Consequently, most studies have focussed on the development of these specialized cells, rather than on the whole lymph node vasculature. Here we have tried to link the functional development of these unique vessels to the development of the lymph node itself. Furthermore, we will discuss how the functionality of these vessels may be regulated and what is known about the genes involved in lymph node formation.