Leucocyte endothelial interactions

Figure 3: Schematic representation of the stages of migration of leucocytes from the circulation to an area of injury observable on microscopy. a) denotes the normal situation. In b) the leucocytes are seen to roll along the endothelium, they appear `sticky'. In c) the leucocytes are tightly adherent to the endothelium and in d) they migrate through the endothelium into the interstium. In the transmigration stage there are gaps formed between the endothelial cells and in the underlying basment membrane.

One of the responses of the body to injury is to recruite leucocytes to the site of injury. The accumulation of leucocytes in damaged tissues depends upon the interaction of leucocytes with the endothelium in the damaged tissue, see figure 3. There is a continuum between the stages of rolling, adherence and transmigration.

Most of the manifestations of inflammation in a tissue, (leucocyte accumulation, filtration of fluid and protein) only occur in the post capillary venule.