pro-B cell early pro-B cell 2010-04-28T11:19:11Z A pro-B cell that is CD22-positive, CD34-positive, CD38-positive and TdT-positive (has TdT activity). Pre-BCR is expressed on the cell surface. Cell is CD19-negative, CD20-negative, complement receptor type 2-negative and CD10-low. D-to-J recombination of the heavy chain occurs at this stage. Markers are commonly associated with human cells. These cells are also reportedly CD21-negative. Transcription factors: PU.1-positive, Ikaros-positive, E2A-positive, and PAX5-positive.