FIG. 1.

HTLV-1-infected T lymphocytes reduce glutamate uptake in rat and human astrocytes via released soluble factors. (A) Kinetic parameters of tritiated l-glutamate uptake by astrocytes. Uptake fits to a hyperbolic model. Each point represents a mean obtained from three experiments. (B) Glutamate uptake was assayed using tritiated l-glutamate (black bars) or its nonmetabolizable analogue tritiated d-aspartate (grey bars). Glutamate uptake by astrocytes was decreased by all treatments (direct contact with infected T cells or use of inserts containing infected T cells, allowing only soluble factors to diffuse) except contact with the noninfected CD4 T lymphocytes, CEM (left). Human primary astrocytes were more sensitive than rat astrocytes or a human cell line. Results are expressed as percentage of glutamate uptake in treated versus naive astrocytes. Numbers of experiments, from left to right: 3, 9, 3, 3, 3, 3, 9. Student's t test was used to evaluate statistical significance. ∗, P < 0.05; ∗∗, P < 0.01; ∗∗∗, P < 0.005; ∗∗∗∗, P < 0.001.