Although monoclonal antibodies (mAbs) targeting CTLA-4 or PD-1, such as Ipilimumab or Nivolumab and Pembrolizumab, have already been successfully established as new tools for treating several types of cancer including lymphoma (reviews in [7–10]), the underlying tumor-suppressive mechanisms are not yet completely understood. The gene discussed is CTLA4; the disease is lymphoma.