Rituximab, an anti-cancer drug targeting the membrane protein CD20, was the first approved therapeutic antibody against B tumor cells. Immunologists at the University of Freiburg have now solved a mystery about how it works. A team headed by Professor Dr. Michael Reth used cell cultures, healthy cells, and cells from cancer patients to investigate how CD20 organizes the nanostructures on the B cell membrane. If the protein is missing or Rituximab binds to it, the organization of the B cell surface changes. The resting B cell is activated in the process. The team has published the research in the journal PNAS.