CD28 and B-cell non-Hodgkin lymphoma: First, we cite the work of Afshar-Sterle and coworkers showing that although deregulated expression of the BCL6 oncogene is observed in many B-cell lymphoma patients, deliberate overexpression of this gene in mice does not cause lymphoma unless CD28- and Fas-ligand activities are simultaneously impaired in CD8+ Tc cells [5].