2. BCR coreceptor Help and strengthen the BCR-Ag-signaling CD19 B-specific surface marker sIgnal transduction CD21 CR2, receptor for C3d-bound Ag CD81 BCR-coreceptor ligation induce reversible palmitoylation of CD8 1 to stabilize the cd 9/ C D2 1/CD81 complex JBC2004;279:319732. BCR coreceptor CD19 B-specific surface marker signal transduction CD21 CR2，receptor for C3d-bound Ag CD81 BCR－coreceptor ligation induce reversible palmitoylation of CD81 to stabilize the CD19/CD21/CD81 complex Help and strengthen the BCR-Ag-signaling JBC 2004;279:31973