Abstract: Provided are a B cell-derived iPS cell generated using a convenient technique, a technology for providing a human antibody at low cost using the iPS cell, an immunologically humanized mouse prepared using cells differentiated from the iPS cell, and the like. Also provided are a cloned cell obtained by contacting a B cell with nuclear reprogramming factors excluding C/EBP? and Pax5 expression inhibiting substances, particularly nucleic acids that encode Oct3/4, Sox2, Klf4 and c-Myc, wherein the cloned cell has an immunoglobulin gene rearranged therein and possesses pluripotency and replication competence (B-iPS cell).

Abstract: Provided are a new method of producing cells having characteristics of hematopoietic stem/progenitor cells, for use in hematopoietic stem cell transplantation, and hematopoietic stem/progenitor cell-like cells produced by the method. Provided in particular are a method of producing hematopoietic stem/progenitor cell-like cells retaining differentiation pluripotency and self-replication potential, comprising (1) a step for providing a mammalian pro-B cell or progenitor cell thereof, and (2) a step for culturing the cell (1) above under conditions for induction of differentiation into B cells, wherein the function and/or expression of the transcription factor E2A is suppressed at least at the stage of pre-pro-B cells or pro-B cells in the process (2) above; a hematopoietic stem/progenitor cell-like cell produced by the method; and an immunotherapeutic agent comprising the hematopoietic stem/progenitor cell-like cell, and the like.