Five (cultured on OP9-Mock for 5 days, left panels) or 10 days (cultured on OP9-Mock for 10 days, right panels) after co-cultured on OP9-Mock cells following the infection, pro-B cells were cultured again on OP9-Mock (Mock) or OP9-Dll4 (Dll4) stromal cells for 3 days. Here, DLL4 is linked to infection.