CNS engraftment of sorted subpopulations of leukemic blasts. Sorted and unsorted leukemic blasts from 6 primografts (#4540, #M120, #WB51, #HV101, #737c, and #758b) were injected intrafemorally, at limiting dilutions, into the femurs of 1 to 4 mice each. CNS involvement was assessed histologically after transplant of 10 to 1500 cells (A) or different immunophenotypic subpopulations of leukemic blasts (B). Black bars represent the number of mice in each experimental group with evidence of CNS involvement (CNS+) on histology. White bars represent number of mice without any visible CNS infiltration (CNS−). Individual results of mice injected with each cell number/immunophenotypic subpopulation for the different primografts are given in supplemental Table 3.