FIG. 7.

HTLV-3 SU binds to naïve CD4⁺ T cells. Naïve CD4⁺ T cells, activated T cells (both CD4⁺ and CD8⁺), and red blood cells were isolated from adult PBMCs. The naïve cells were left under the conditions to keep them unactivated, and the red blood cells were left as a pellet, both at 4°C. The T cells were stimulated by culturing them at 37°C in RPMI media containing 10% sera, phytohemagglutinin, and IL-2. The levels of SU binding and GLUT-1 expression were determined 24 h later. (A) SU binding on naïve CD4⁺ T cells (top) and activated T cells (bottom). Note that the level of HTLV-2 SU binding for the naïve cells is below that of the negative control (ASLV-A SU). Shown is a representative result of three independent experiments. (B) Cell surface expression of GLUT-1 on naïve CD4⁺ T cells (left), activated T cells (middle), or red blood cells (right), which express high levels of GLUT-1. The level of GLUT-1 was determined using two independently derived antibodies that recognize extracellular domains of human GLUT-1: a mouse anti-human monoclonal antibody from R&D Systems (top) and a rabbit anti-human polyclonal from Alpha Diagnostics (bottom).