FIG. 7.

Activated T cells become susceptible to suppression by rLTB when they return to a resting state. Long-term MHC antigen-specific CD4 and CD8 T-cell lines were established from MLR cultures as described in Materials and Methods. The T-cell lines were allowed to rest for 10 days and then washed free of rIL-2 and exposed to rLTB (solid bars), or they were reactivated with specific allostimulator cells 48 h prior to treatment with rLTB (open bars). The cells were exposed to rLTB (0.1, 1, and 10 μg/ml) for 2 h, washed, and reincubated. The number of viable cells remaining after 48 h was determined by quantitative flow cytometry with the SCDA assay. Data are presented as the percent change from values for untreated (no-rLTB) control cultures: viable cells in resting CD4 cells, 18,037; in resting CD8 cells, 14,047; in activated CD4 cells, 58,592; in activated CD8 cells, 50,858. Negative values indicate a decrease in cells; positive values indicate an increase from control levels.