Fig. 8. Model of min-Plg-mediated apoptosis in ECs. Our findings indicate that the complex between CD87 and CD222 is a platform for the activation of LTGF-ß. We have shown that mini-Plg, a proteolytic fragment of Plg, can induce TGF-ß activation followed by apoptosis in ECs. Based on our data and the studies of other laboratories (Cornelius et al., 1998; Godar et al., 1999; Morikawa et al., 2000; Scapini et al., 2002), we propose that, under certain pathological conditions, such as inflammation or cancer, the inactive proenzyme Plg is converted to mini-Plg upon binding to CD222 (e.g. by elastase or cathepsin D). Because CD222 associates with CD87 in ECs, the CD87-bound uPA can convert the CD222-bound mini-Plg to the active protease mini-Plm. This leads to partial digestion of LTGF-ß bound to CD222, followed by the release of the active TGF-ß, inducing apoptosis in ECs.