PERICYTES IN HUMAN BREAST STROMA AND THE CELLS TO WHICH THEY RELATE

The function of pericytes, the cells nearest the microvascular endothe lium, has long been debated. On the basis of ultrastructural studies i t is pointed out that they have specialised features in common with en dothelial cells of the lymphatic labyrinth of the human breast. The la tter are in continuity with the initial lymphatics. These features, wh ich include points of stromal attachment, allow contraction or relaxat ion of the cell-processes. The cytoplasmic processes of the pericyte, when relaxed, form areas of contact with the blood vascular endotheliu m. Subsequent contraction may lead to loss of contact and increase in the area of vascular endothelium available for diffusion. The pericyte is thus equipped to act as a regulatory link between the blood vascul ar endothelium and that of the fine lymphatic system.