Clonality of the lymphoid tumors as demonstrated by immunoglobulin gene rearrangement studies. Southern blot analysis of some lymphoid tumors showing immunoglobulin gene rearrangement. Three different lymphomas (labeled 1-3) were digested with EcoRI and HindIII as indicated. C, control liver DNA from one of the mice; T, DNA from a T-cell lymphoma showing no rearrangement for the immunoglobulin gene. Germline band is indicated by a dash on the side.