(A and B) Schematic diagrams of the interaction between neighboring fluorescent probes targeted to the raft or the non-raft membrane fraction of the plasma membrane, and PH(PLC-δ), a PI(4,5)P2 reporter. CD4+ T cells were incubated with lentivirus containing (C) Lck(N10)/PH(PLC-δ) (n = 4 per diet), or (D) Src(N15)/PH(PLC-δ) (n = 4 per diet) before FRET by acceptor photobleaching. FRET efficiency (E%) was determined as described in Fig 1 (*P < 0.05 between genotypes). (E) Splenic CD4+ T cells were stained with CFSE, then cultured (n = 6 mice per diet) either in unstimulated or stimulated conditions for 72 hrs in triplicate. Cells were collected and gated by propidium iodide staining to exclude dead cells. Proliferation Index was calculated using ModFitLT 3.2 [37]. Different letters represent statistically significant differences between the groups after one-way ANOVA followed by Tukey post-hoc test (P < 0.05).