In vitro models of lymphocyte transendothelial migration.

The processes of lymphocyte-endothelial cell interaction and the in vitro assays employed in their study are the subjects of this review. In motility assays in porous filters and gel matrices, it has been shown that lymphocyte migration can be modulated by interleukin-2 (IL-2), IL-3, IL-4, IL-6, and IL-8. Cytokines can also modulate lymphocyte-endothelial adhesion. Endothelial intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) are induced or upregulated by IL-1 or tumor necrosis factor. In addition, interferon-gamma upregulates ICAM-1, and IL-4 can induce VCAM-1. The roles of these cytokines and adhesion molecules in transendothelial migration may be studied in assays in which lymphocytes penetrate layers of cultured endothelial cells. These models can distinguish lymphocyte adhesion from subsequent migration. Using such models, we and others have obtained evidence that both lymphocyte function-associated antigen-1 (LFA-1)/ICAM-1 and very late activation antigen 4 (VLA-4)/VCAM-1 interactions mediate lymphocyte adhesion to endothelial cells, but that LFA-1/ICAM-1 interactions play a greater role in transendothelial migration.