Over the last year we continue to make substantial progress in our project on differentiating pluripotent stem cells into thymic epithelial progenitors (TEP’s). We have now developed a robust differentiation protocol that improves expression of the key TEP transcription factor Foxn1. In addition, we have also made progress in generating more fully humanized immune system mice by grafting in our TEP’s with hematopoetic stem cells. Preliminary results from these in vivo experiments indicate that our TEP’s are capable of inducing T cell development. We are now further refining our technique to improve this efficiency and also other methods to induce Foxn1 expression in TEP’s. Taken together, these results will provide the platform for potentially bringing this approach to the clinic.