GIFT15 and biochemical responses. (A) GIFT15 and splenocyte apoptosis. Splenocytes cultured for 36 hours in the presence of equimolar concentrations of cytokines were stained for PI and annexin-V. The same conditions were applied for Bcl-XL immunoblotting. α-Tubulin was used as loading control for this experiment. (B) Splenocyte proliferation. Splenocytes (10⁵) were cultured with increasing concentrations of cytokines for 72 hours before MTT incorporation. Results are shown as mean of triplicates ± SEM of 1 representative experiment of 2 independent assays (P < .05 between rIL-15 [▪], rIL-15 + rGMCSF [X], GIFT15 [□], and rGMCSF [▴], or GFP CM [⋄]). (C) Splenocyte activation and secretion of IFNγ. The supernatant of 10⁵ splenocytes cultured for 36 hours in the presence of GFP CM inoculated with cytokines or GIFT15 CM was used to detect the presence of IFNγ by ELISA. Results are shown as mean of quadruplicate ± SED of 1 representative experiment of 5 (nd = not detected; P < .005 between rIL-15 or rIL-15 + rGMCSF and GFP control group).