Differential Activation-Dependent Regulation of Integrin Function in Cultured Human T-Leukemic Cell Lines

Abstract

AbstractT lymphocytes isolated from human peripheral blood express β1 (VLA) and LFA-1 integrins, but strong binding to integrin ligands occurs only after the delivery of an activation stimulus to the T cell. To gain further insight into activation-dependent regulation of integrin function, we have analyzed integrin activity on three different T-leukemic cell lines: Jurkat, CEM, and H9. This analysis shows important mechanistic differences in integrin regulation. First, phorbol ester treatment results in increased β1 integrindependent adhesion of both Jurkat and CEM cells to fibronectin, but decreased adhesion of H9 cells. Second, certain activation stimuli that upregulate β1 integrin activity in peripheral T cells are nonfunctional in these T-cell lines. Third, analysis of a panel of Jurkat mutants lacking surface expression of CD2 and/or CD3 shows that CD2-mediated upregulation of β1 integrin activity is dependent on expression of CD3, whereas CD28-mediated upregulation is not dependent on either CD2 or CD3 expression. Fourth, all T-cell lines tested show an inability to adhere to purified ICAM-1 via LFA-1. The selective alterations in integrin regulation in these cell lines relative to peripheral blood T cells provide important insights into the intracellular processes involved in integrin activation.