Veto activity of ex vivo–expanded CD34+ cells: determination of veto activity at different ratios of veto to responder cells
| Experiment . | CD34 veto cells (veto-responder ratio)3-150 . | MLR against donor A . | MLR against donor B . | |||
|---|---|---|---|---|---|---|
| Before culture . | After culture . | CTL activity (% responding cultures)3-151 . | Veto activity (% inhibition)3-152 . | CTL activity (% responding cultures)3-151 . | Veto activity (% inhibition)3-152 . | |
| 1 | — | — | 87.5 | — | 93.75 | — |
| 0.5 | — | 18.75 | 79 | 62.5 | 33 | |
| — | 0.5 | 6.25 | 93 | 50 | 47 | |
| — | 0.25 | 18.75 | 79 | 62.5 | 33 | |
| 2 | — | — | 62.5 | — | 100 | — |
| — | 0.25 | 6.25 | 90 | 100 | 0 | |
| — | 0.125 | 0 | 100 | 100 | 0 | |
| Experiment . | CD34 veto cells (veto-responder ratio)3-150 . | MLR against donor A . | MLR against donor B . | |||
|---|---|---|---|---|---|---|
| Before culture . | After culture . | CTL activity (% responding cultures)3-151 . | Veto activity (% inhibition)3-152 . | CTL activity (% responding cultures)3-151 . | Veto activity (% inhibition)3-152 . | |
| 1 | — | — | 87.5 | — | 93.75 | — |
| 0.5 | — | 18.75 | 79 | 62.5 | 33 | |
| — | 0.5 | 6.25 | 93 | 50 | 47 | |
| — | 0.25 | 18.75 | 79 | 62.5 | 33 | |
| 2 | — | — | 62.5 | — | 100 | — |
| — | 0.25 | 6.25 | 90 | 100 | 0 | |
| — | 0.125 | 0 | 100 | 100 | 0 | |
MLR indicates mixed lymphocyte reaction; and CTL, cytotoxic T-lymphocyte.
Responder cells and irradiated stimulator cells (from donor A or donor B) were cocultured for 5 days in the absence or presence of CD34 cells from donor A, obtained before and after culture (for 7 days in experiment 1 and 10 days in experiment 2). The responder cells were then cultured again for 7 days under limiting dilution in microtiter plates.
Wells were scored positive for CTL activity when chromium release exceeded the mean spontaneous release value by at least 3 SDs from the mean. Data are the percentages of responding cultures in experiments 1 and 2 at cell concentrations of 1 × 104and 4 × 104 responder cells/well, respectively.
Veto activity of tested cells was evaluated by assessment of their capacity to inhibit alloreactive CTL precursors in the MLR to which they were added at the indicated ratios of veto to responder cells.