Restoration of T- and NK-cell development in human SCID-X1 cells by the Revgen and the EF1α vectors. For T-cell differentiation, CD34⁺ cells from an SCID-X1 patient were transduced with either the Revgen or the EF1α vector and cultured on an OP9-DL1 stromal cell layer. Double-positive (DP, CD4⁺CD8⁺) as well as CD3⁺TCRγσ⁺ cells were observed on day 27 and day 37, respectively, using flow cytometric analysis. For NK-cell differentiation, CD34⁺ cells from a separate SCID-X1 patient were transduced with the EF1α vector and then cultured in Myelocult. Cells were taken on day 37, and expression of NK-cell marker (CD56) was analyzed by flow cytometry. ND indicates not done.