Effect of tumor promoter 12-O-tetradecanoyl-phorbol l3-acetate on CD 7 expression by T lineage cells

✍ Scribed by Lawrence K. L. Jung; Shu Man Fu

• Publisher: John Wiley and Sons
• Year: 1988
• Tongue: English
• Weight: 518 KB
• Volume: 18
• Category: Article
• ISSN: 0014-2980
• DOI: 10.1002/eji.1830180509

✦ Synopsis

Effect of tumor promoter 12-0-tetradecanoyl-phorboll3-acetate on CD 7 expression by T lineage cells*

Phorbol esters exert diverse effects on cellular activation and differentiation. CD 7, a differentiation antigen appearing early in T cell ontogeny, may be involved in the activation and differentiation processes. CD 7 was found to be rapidly down-regulated by 12-0-tetradecanoylphorboll3-acetate (TPA) from mature T cell surface. The time course of CD 7 down-regulation was similar to that of other functionally important T cell antigens, CD 3 and CD 4. Within 2 h, TPA at 10 to 30 ng/ml induced a complete down-regulation of CD7. Twenty-four hours later, the reappearance of CD7 on TPA-treated cells was observed. This phenomenon was monocyte independent. In contrast, CD7 expression on thymocytes was resistant to the effect of TPA. In addition, certain leukemic T cells were also resistant to TPA-induced CD 7 down-regulation. The mechanism underlying TPA-induced CD 7 down-regulation was investigated further. Synthetic diacylglycerol, sn-l,2-dioctanoylglycero1, which activates protein kinase C, did not induce down-regulation of CD 7 on mature T cells. Ionomycin, a calcium ionophore, did not down-regulate this antigen either. Thus, it is concluded that the processes of protein kinase C activation andlor cytosolic calcium influx are not sufficient for TPA-induced CD 7 down-regulation; other pathways induced by TPA may be responsible.