Résumé
We have distinguished five TNF-α-inducible cell adhesion mechanisms on microvasculature-derived endothelioma cells of the mouse which mediate the binding of different types of leukocytes. Three of these mechanisms could be identified as the mouse homologs of ICAM-1, VCAM-1, and E-selectin, of which the latter was defined by the novel mAb 21KC10. The fourth TNF-α-inducible cell adhesion mechanism was blocked by antibodies specific for mouse P-selectin. We have recently shown that TNF-α stimulates the synthesis of P-selectin in mouse endothelioma cells. Here we show that this stimulation leads to maximal cell surface expression levels within 4 h after stimulation while the same endothelioma cells are also able to upregulate P-selectin at the cell surface within minutes after stimulation with PMA. Both effects are additive. The fifth TNF-induced cell adhesion mechanism is defined by mediating the binding to the mouse monocyte/macrophage cell line J774. This adhesion mechanism is not inhibited by antibodies against any of the other four CAMs; it functions well at 7°C (in contrast to ICAM-1 and VCAM-1) and it is as active after 16 h of TNF induction as after 4 h (in contrast to E- and P-selectin). Furthermore, this new adhesion mechanism only functions on two of three endothelioma cell lines and is undetectable on the third, although ICAM-1, VCAM-1, E-selectin, and P-selectin could be demonstrated to function well on this cell line. Thus, in addition to the three known TNF-inducible CAMs, ICAM-1, VCAM-1, and E-selectin, also P-selectin and a fifth, as yet molecularly undefined cell adhesion mechanism, are TNF inducible at the cell surface of mouse endothelioma cells.