The diapédèse is the mechanism by which a Leucocyte penetrates between the cells endothéliales of a blood Capillaire in answer to chemical signals inflammatory.

It can be done in two ways:

1. Is the cell passes between two cells endothéliales by local dissociation of the systême of junction. The cell passes in the space created between the two separate cells endothéliales. The systêmes of junction are positioned back then. This phenomenon requires specific interactions between the various cells via molecules of surface.

2. Is the cell passes by meshs of the fabric endothélial. It is the case in hematopoietic or hematogen osseous marrow, where the mature cells pass by spaces between the cells endothéliales. These vessels having of the openings are called capillary sinusoids. Here, there is not thus dissociation of the systêmes of junction.

This phenomenon makes enter in plays molecules of adhesions (Intégrine S, Lectine S, Sélectine S) and phenomena of Chimiotaxie.