FIG. 6.

Cell-to-cell contact is required for killing. In a ⁵¹Cr release assay, we used TMEV-induced autoreactive cells as effector cells and the syngeneic PSJL cell line as target cells at an E/T ratio of 100. (a) Double-chamber experiments. Effector cells (•) were placed in the lower compartment of the Transwell chamber, and ⁵¹Cr-labeled target cells (○) were placed either in the same compartment as the effector cells or in the upper compartment of the Transwell chamber. Target cell lysis did not occur when effector and target cells were separated. (b) After a 5-h incubation of TMEV-induced autoreactive cells with syngeneic PSJL cells at E/T ratios of 100, 33, and 11 or with no effector cells, supernatants were harvested from the cultures. ⁵¹Cr-labeled PSJL cells were incubated with the supernatants, regular RPMI 1640 medium, or Triton X-100 (maximum release), for 5 h. No cytotoxic activity was seen in the supernatants. Results are representative of those from two independent experiments. Error bars indicate standard errors.