Immature CD11b⁺/CD31⁺ cells retain the ability to proliferate in the presence of cytokines.

CD11b⁺ splenocytes from mice bearing a TS/A tumor were enriched with antibody-coated magnetic beads. The cells were plated in triplicate (20 000 cells per well) and then exposed to no cytokines, IL-4 (100 ng/mL), GM-CSF (20 ng/mL), or a combination of GM-CSF and IL-4. After 4 and 9 days of culture (A and B, respectively), cells were pulsed with ³H-TdR, and harvested 18 hours later. Irradiated cells were included as the negative control. (C)³H-TdR incorporation by CD11b⁺ cells further sorted into CD31⁺ and CD31⁻ cells by FACS and cultured for 5 days with the various cytokines. Data are from triplicate wells ± SD.