BCR and infection: Figure S4 exemplary shows the flow cytometric analysis of HEL-IgM-BCR transduced donor stem cells at either 24 hours or 5 days post-transduction. Transduction rate was ∼6% (as expressed by GFP+ cells) at 24 hrs post-infection. The percentage of GFP+ cells was even increased after further 4 days in culture along with the percentage of GFP+CD19+ cells, indicating the stem cells would at least partly develop into the B cell lineage.