A unique monoclonal antibody mNI-11 rapidly enhances spread formation in human umbilical vein endothelial cells

We previously reported a novel monoclonal antibody (MAb), designated mNI-11 , recognizing an adhesion-associated antigen distinct from any previously r eported ones. In this article, this adhesion-associated antigen with a mole cular weight of about 97 kDa was found to be strongly expressed on human um bilical vein endothelial cells (HUVECs) by fluorescence-activated cell sort er (FACS) analysis. Expression of this antigen on HUVECs was slightly incre ased in response to the exposure to tumor necrosis factor-alpha (TNF-alpha) or phorbol myristate acetate (PMA). As a biological function exerted by th is antigen, it was of great interest that immobilized mNI-11 directly and r apidly enhanced the spread formation of HUVECs, whereas MAbs binding other adhesion-associated antigens such as mNI-58A (anti-CD11a), L130 (anti-CD18) , L133.1 (anti-CD31), L178 (anti-CD44), L25.3 (anti-CD49d), or LB-2 (anti-C D54) did not carry such activity under the same conditions. The HUVECs spre ad formation enhanced by mNI-11 was completely blocked in the presence of a microfilament formation inhibitor, cytochalasin D (CyD), a Ca2+-calmodulin inhibitor, W-7, EDTA, and was partially blocked by a microtubule formation inhibitor, nocodazole, a protein kinase C (PKC) inhibitor, H-7, and a prot ein synthesis inhibitor, cycloheximide (CHX). However, a protein tyrosine k inase (PTK) inhibitor, genistein, did not affect the spread formation under the same conditions. Taken together, it was suggested that the spread form ation of HUVECs enhanced by mNI-11 was mainly associated with the influx of Ca2+ and microfilament reorganization. In addition, the novel property ass ociated with mNI-11 to enhance the spread formation of HUVECs was possibly mediated through its reaction against a unique epitope on HUVECs.