Treatment of human T-cell leukemia virus type I (HTLV-I)and HTLV-II-infected T-cell lines with 12-0-tetradecanoylphorbol-13-acetate (TPA) stimulated virus release. However, this stimulation was mainly detected at 42 to 48 h of treatment, whereas later virus release declined rapidly. During the first 48 h, TPA had no effect on cell growth, but later, the number of viable cells was profoundly lower in the TPA-treated than in the untreated cultures. This shift in virus release and cell number resulted from self-fusion of a large proportion of the virus-producing cells, which seemed to consequently enter into a dying process. This fusion, which resulted in syncytium formation, was strongly inhibited by anti-HTLV-I env monoclonal antibodies. Furthermore, no self-fusion was detected in three different uninfected T-cell lines similarly treated with TPA. On the other hand, stimulation of virus production by 3-methylcolanthrene (3-MC) treatment failed to induce self-fusion in the infected cells. Moreover, no syncytium was detected when these 3-MC-treated infected cells were cocultured with any of the TPA-treated uninfected cells. The effects of TPA on virus production and syncytium formation were both abolished by three different protein kinase C inhibitors. Taken together, these data suggest that the self-fusion observed in these experiments required both enhanced virus production and protein kinase C-phosphorylated viral or/and virally induced cellular component(s).

Neoplastic proliferation of the meibomian glands is most often characterized by a tarsal tumor of the eyelid conjunctiva, having the clinical appearance of a chalazion. As such, the tumor is frequently not recognized as a neoplasm and is treated conservatively as an inflammatory lesion. A protracted clinical course combined with repeated surgical excisions typify this slow-growing tumor of sebaceous gland cells. In addition to the usual features of polygonal cell shape, abundant cytoplasm, and numerous fat vacuoles, we describe the presence of a peculiar nuclear inclusion seen only in the parenchymal cells of this tumor, and having the appearance of concentric layers of electron-dense material surrounding an opaque electron lucent core.