Determination of JMML cell engraftment in SCID/NOD mice using Southern blot analysis of bone marrow DNA. Lanes 1 and 2 refer to untreated mice 4 and 6 weeks posttransplant. The other data are from transplanted mice receiving early or late treatment with either E21R alone (lanes 3 and 4), or MoAb cA2 alone (lanes 5 and 6), or mice receiving 4 weeks treatment with E21R and MoAb cA2 starting at the time of transplantation (early treatment, lane 7), or 4 weeks posttransplant (late treatment, lane 8). Each lane shows blot of bone marrow DNA from one individual mouse and is representative of at least four other mice. The characteristic 2.7-kB band indicating a human specific DNA sequence, is shown to the left, and the percentages of human-derived DNA were estimated from the known human/mice mixtures as indicated.