BCR oligomerization–induced conformational changes in the BCR’s cytoplasmic domain are affinity dependent. FRET efficiencies between FRET donor Igα-YFP and FRET acceptor μ-CFP are given at the indicated time points for μ-High or μ-Low J558L cells placed on lipid bilayers containing NIP1-His12. (A) Means ± SD of FRET efficiencies are given over a time course of 240 s. (B and D) Statistical comparisons for the maximal changes in FRET (ΔFRET) from 0 and 200 s (B) and the time needed to reach maximal FRET efficiency (D) are given for μ-High and μ-Low J558L cells. (C) The half-life of FRET loss (τ₅₀) of FRET efficiencies from maximal FRET levels in both μ-High and μ-Low J558L cells were acquired by fitting the FRET loss plot of individual cells into a monoexponential decay function, as detailed in Materials and methods. The bars represent means ± SD from 14 μ-High and μ-Low J558L cells in three independent experiments. Two-tailed t tests were performed for the statistical comparisons in B–D.