Dissection of murine lymphocyte-endothelial cell interaction mechanisms by SV-40-transformed mouse endothelial cell lines: novel mechanisms mediating basal binding, and alpha 4-integrin-dependent cytokine-induced adhesion.

Lymph node-derived endothelial cells were immortalized by infection with SV40 virus and subclones expressing the marker MECA 325 specific for high-endothelial venules (HEV) were selected. These transformed mouse endothelial (TME-) cell lines grow permanently without requirement for special growth factors. Staining of the selected clones with endothelium-specific antibodies and with anti-von Willebrand factor antiserum and uptake of acetylated low-density lipoprotein provide evidence for their endothelial origin. The vascular addressins identified by mAbs MECA 79 and MECA 367 on HEV are not detectable, indicating that the phenotype of the cells differs from that of HEV-type endothelium. The TME cells display a constitutive capacity to bind lymphocytes. An additional binding component is induced by treatment of the TME cells with TNF alpha. Antibodies against the homing receptor LECAM-1 (lectin-related leucocyte-endothelial cell adhesion molecule 1), alpha 4-integrins, vascular addressins, LFA-1, or ICAM-1 known to block lymphocyte interaction with particular types of HEV were unable to inhibit the basal adhesion to TME cells, indicating that a further binding mechanism in mice is displayed by this cell type. The adhesion component induced by TNF alpha is mediated by alpha 4-integrins since enhanced binding could be blocked by an antibody against mouse alpha 4 (lymphocyte-Peyer's patch adhesion molecule 1/2). TME cell lines therefore seem to be a useful model for the dissection and analysis of hitherto poorly characterized murine lymphocyte/endothelial cell interaction mechanisms.