develops from develops from precursor B cell early pro-B cell late pro-B cell 2010-04-28T12:06:06Z Late pro-B cells are also reportedly CD10-positive, CD20-negative, CD21-negative, and TdT-positive. Transcription factors: PU.1-positive, Ikaros-positive, E2A-positive, and PAX5-positive. A pre-B cell precursor is CD19-low, CD22-positive , CD34-positive, CD38-positive.