In preferred embodiments, the stably tethered structure may comprise combinations of anti-CD74 X anti-CD20, anti-CD74 X anti-CD22, anti-CD22 X anti-CD20, anti-CD20 X anti-HLA-DR, anti-CD19 X anti-CD20, anti-CD20 X anti-CD80, anti-CD2 X anti-CD25, anti-CD8 X anti-CD25, and ...