Freshly isolated CD34⁺CD33^lo postnatal thymocytes (experiment no. 1) were plated by limiting dilution and cultured with a mixture of IL-7, IL-1α, IL-6, SCF, GM-CSF, and IL-2, as described in the Materials and Methods. After a total culture period of 16 days, all wells were microscopically inspected for the presence of live hematopoietic cells reactive with anti-CD56-coated magnetic beads (NK cells) or unreactive with anti-CD56-coated beads but displaying a typical dendritic morphology (DCs). In experiments no. 2 and 3, CD34⁺CD33^lo thymocytes were first cultured at high density for 3 and 4 days, respectively, with the cytokine mixture described for experiment no. 1 lacking IL-2. Afterwards, recovered cells were phenotyped (88% and 90% CD34⁺CD44^brightCD56⁻, in experiments no. 2 and 3, respectively), plated by limiting dilution, and cultured for 16 additional days with the cytokine mixture either with or without IL-2. Positive wells were analyzed for the presence of DCs and/or NK cells as described for experiment no. 1.