2. Co-receptors CD19/CD2 1/CD81complex CD2 1=CR2 C3dR. EB virus r CD19/CD21/CD8 1 interactions with complement associated with antigen play a role in antigen induced B-cell activation2. Co-receptors CD19/CD21/CD81complex CD21=CR2, C3dR, EB virus R CD19/CD21/CD81 interactions with complement associated with antigen play a role in antigen￾induced B-cell activation