FIG 5.

Measurement of Vγ9Vδ2 T-cell stimulation bioactivity in iRBC supernatants. Dose-response stimulation of two different γδT-cell lines with either HMBPP expressed as a concentration and corresponding quantities in the assays (A) or supernatant of fully ruptured iRBCs (see Materials and Methods) and the theoretical corresponding number of contributing iRBCs in the assay, extrapolated from the dilution factor (B). After stimulation, CD107a surface expression was assayed. Vγ9Vδ2 T-cell activation obtained with culture supernatants J, K, and L and uiRBC supernatant are shown. Data represent means ± SD from duplicates. Titration of the rupture supernatant with one γδT-cell line was calculated at half of the maximum of the percent CD107a⁺ Vδ2⁺, which was obtained after stimulation by both supernatant dilution determined in panel B and the HMBPP concentration determined in panel A. The HMBPP equivalent content of the supernatant corresponds to the HMBPP concentration determined in panel A multiplied by the supernatant dilution factor determined in panel B.