Assessing the roles of galectins in regulating dendritic cell migration through extracellular matrix and across lymphatic endothelial cells

Abstract

Leukocyte migration from the bloodstream into tissues, and from tissues to lymph nodes, depends on expression of specifi c adhesion and signaling molecules by vascular endothelial cells and lymphatic endothelial cells. Tissue damage and microbial infection induce vascular endothelial cells to up-regulate expression of adhesion molecules to facilitate entry of several leukocyte populations from blood into tissues. Many of these cells then leave infl amed tissue and migrate to regional lymph nodes. A critical population that emigrates from infl amed tissue is dendritic cells. Dendritic cells in tissue have to migrate through extracellular matrix and across a layer of lymphatic endothelial cells to enter the lymphatic vasculature. Little is known about the adhesion molecules expressed by lymphatic endothelial cells or the processes required for the critical step of dendritic cell exit from tissues, specifi cally migration through the extracellular matrix and basalto- apical migration across the lymphatic endothelial cell layer into lymphatic vasculature. Members of the galectin family of carbohydrate binding proteins are expressed in both vascular and lymphatic endothelial cells. Dynamic changes in galectin expression during infl ammation are known to regulate leukocyte tissue entry during infl ammation. However, the roles of galectin family members expressed by lymphatic endothelial cells in leukocyte tissue exit remain to be explored. Here, we describe an in vitro transmigration assay that mimics dendritic cell tissue exit in the presence and absence of galectin protein. Fluorescently labeled human dendritic cell migration through extracellular matrix and across human lymphatic endothelial cells is examined in the presence and absence of recombinant human galectin protein.