Figure 3.

DPG rapidly induces a prolonged, but reversible, state of unresponsiveness to IPP. (A) The Vγ9/Vδ2 cell line BCI 31 was incubated with DPG for the time indicated on the x-axis. After extensive washing, the TNF release stimulated by 50 μM IPP (▪) or 1 μg/ml PHA (•) was measured. (B) Vγ9/Vδ2 clone BCI 49 (2 × 10⁶ cells/ml) was incubated in IL-2–free medium with 1 mM DPG overnight and washed extensively. The cells were then rested in medium for the time indicated on the x-axis. Proliferative responses to medium (♦), 100 μM IPP (▪), or 20 U/ml IL-2, (○) are shown. □ indicates control proliferation to IPP (100 μM) of the same cells not preincubated with DPG. Results obtained in four independent experiments using different Vγ9/Vδ2 clones showed recovery of responsiveness after 1 to 5 d. Preincubation with DPG did not affect the responsiveness of CD4⁺ TCR αβ cells to their specific peptide (data not shown).