Localization of BCR in lipid rafts of D1-7 cells. The cells were treated and the soluble and lipid raft fractions prepared similarly as in Figure 5. The Western blots were probed with mAbs specific for human IgM μ chain, CD79a, and CD79b, to reveal the distribution of BCR complexes in the lipid rafts (top 3 panels) and soluble (bottom panel) fractions. The positions of these proteins are indicated on the right. Lane labels are the same as those in Figure 5. Samples loaded per lane for lipid rafts and soluble fractions were prepared from approximately 4 × 106 and 2 × 105 cells, respectively.