tokens: The expression of transiently transfected expression vectors under the control of the long terminal repeat ( LTR ) of the human immunodeficiency virus ( HIV ) or its enhancer sequence and the translocation of the HIV enhancer-binding protein NF-kappa B were analyzed in two human T-cell clones stimulated through their T-cell receptor complex or by tumor necrosis factor or phorbol 12-myristate 13-acetate .