RBCs inhibit activation-induced T-cell death.

(A) PBLs were stimulated in 6-well plates with PHA-P (5 μg/mL) and cultured for 5 days in the absence or presence of RBCs. After the culture period, activated T-cell blasts were stained with PI, and 10 000 cells were acquired in a FACSort and analyzed using the Lysis II program. Based on morphologic (FSC/SSC) and PI labeling characteristics (Figure 1), regions R1 and R2 represent live and dead cells, respectively. The mean percentage of cells gated within each region from 7 separate experiments is indicated. (B) Total number of live blast cells in cultures with (▪) and without (░) RBCs was determined by trypan blue exclusion, as indicated in “Material and methods.” Results show the mean ± SD of 3 independent experiments. *P < .03.