Fig. 3.

In vitro approaches for T-cell generation. Signaling through the receptor Notch, which engages delta-like ligands (DLLs), is pivotal for proT-cell generation. DLLs can be expressed on stromal cells (A), as with the conventional OP9-DL co-culture system. Alternatively, in serum-free and stromal cell-free approaches, which are amenable for clinical translation, Notch ligands can be immobilized to polystyrene plates (B) or presented on magnetic microbeads (C) for engaging Notch on developing thymocytes. Microbeads can be extracted from the system using magnetic forces.