IL-2–independent activation of γδ T cells induced by IPP or pamidronate.

Expression of the activation markers CD25 (A) and CD69 (B) was measured on γδ T cells after stimulation of primary PBMC with IPP (4 μmol/L) or 3 different pamidronate concentrations (0.4 μmol/L, 4 μmol/L, 40 μmol/L) without exogenous IL-2. Percentage of CD25⁺ or CD69⁺ γδ T cells was determined by 2-color FACS analysis using anti-CD25 or anti-CD69 mAb and anti-γδ TCR mAb before (0 hour) and after (24, 48, and 72 hours) culture. In control cultures (medium alone) no significant up-regulation of CD 25 or CD69 was detected during the culture period (data not shown). Results represent mean values ± SD of triplicate cultures of 1 representative PBMC donor. Similar activation profiles were observed in 6 healthy donors.