Figure 2.

Survival of mice injected with clonally-derived pre-B cells. A and C schematically summarize the protocols for generating clones derived from single cells, whereas B and D illustrate the data. (A) Arf-null bone marrow cells transduced with p185 were cultured for 8 d to generate pre-B cells. These were subcloned from single cells and expanded for 3 wk, and 20 cells from six randomly chosen clones were infused into cohorts of five syngeneic mice. All such clones contained single proviral insertions and exhibited rearranged Ig heavy-chain alleles. Animals were monitored daily for disease and sacrificed when moribund. (B) Survival curves generated from the experiment summarized in A. (C) To further limit the period of in vitro manipulation, six primary cultures of Arf-null bone marrow cells were transduced with p185 and grown under B-cell selective conditions. Eight days later, single cells derived from each primary culture were seeded into individual microwells using an automated cell sorter. Five colonies appearing after only six additional days of culture, each containing ∼50 cells and chosen at random from each 96-well dish, were injected into individual mice (total, 30). (D) The time course and percentage of clones inducing fatal ALL from the experiment outlined in C are indicated.