Induced pluripotent stem (iPS) cells offer a unique potential for understanding the molecular basis of disease and development. Here we have generated several human iPS cell lines, and we describe their pluripotent phenotype and ability to differentiate into erythroid cells, monocytes, and endothelial cells. More significantly, however, when these iPS cells were differentiated under conditions that promote lympho-hematopoiesis from human embryonic stem cells, we observed the formation of pre-B cells. These cells were CD45 ؉ CD19 ؉ CD10 ؉ and were positive for transcripts Pax5, IL7␣R, -like, and VpreB receptor. Although they were negative for surface IgM and CD5 expression, iPS-derived CD45 ؉ CD19 ؉ cells also exhibited multiple genomic D-J H rearrangements, which supports a pre-B-cell identity. We therefore have been able to demonstrate, for the first time, that human iPS cells are able to undergo hematopoiesis that contributes to the B-cell lymphoid lineage. (Blood. 2011;117(15): 4008-4011) IntroductionReprogramming of adult human somatic cells toward induced pluripotent stem cells 1-3 is a groundbreaking technology that opens the way for the development of novel diagnostics and therapeutics. Although traditionally human embryonic stem (hES) cells have been used as a convenient tool with which to understand hematopoietic and lymphoid development in health and disease, the usefulness of human induced pluripotent stem (iPS) cells for this purpose has recently been questioned. 4 For hES cells, a limited number of studies have derived B cells 5 and T cells, 6,7 with some reports suggesting why this might be difficult to achieve, 8 and which has not been described thus far for B cells from human iPS cells. Development of lymphoid progenitors from such pluripotent sources is of particular interest because it will help to understand better the early stages of B-cell development, which is currently not well understood. 9 This includes which B cells are formed and when and how these lineages relate to the formation of both normal and leukemic progenitors during development. 10,11 Methods Derivation, identification, and maintenance of human iPS cell lines iPS cells were generated essentially as decided by Takahashi et al, 1 with changes highlighted herein. pMX vectors hOct4, hSox2, and hKlf4 were purchased from Addgene and viral supernantants for each transgene produced in pantropic PLATGP packaging cells (Cell Biolabs). Transduced Normal Human Dermal Fibroblasts (NHDFs; Lonza Biologics) were cocultured with mitomycin C-treated mouse embryonic fibroblasts in modified embryonic stem cell media (Dulbecco modified Eagle medium/ F12, 20% [v/v] Knock Out Serum Replacement, 10 ng/mL basic fibroblast growth factor, 2mM sodium pyruvate, 1ϫ nonessential amino acids [Invitrogen], and 1M mercaptoethanol [Sigma-Aldrich]). Cultures were routinely maintained in 5% CO 2 and 5% oxygen with half-media changes every 2 days, for up to 34 days. iPS colonies were picked and expanded before adaptation to feeder independent culture as describ...

We developed a chemically defined system to generate unlimited numbers of DCs from hESCs. Our results demonstrate that hESC-derived DCs generated from this process are immunogenic and have the potential to be used for DC immunotherapy.

Monocyte-derived dendritic cells (moDC) have been widely used in cancer immunotherapy but show significant donor-to-donor variability and low capacity for the cross-presentation of tumour-associated antigens (TAA) to CD8 þ T cells, greatly limiting the success of this approach. Given recent developments in induced pluripotency and the relative ease with which induced pluripotent stem (iPS) cell lines may be generated from individuals, we have succeeded in differentiating dendritic cells (DC) from human leukocyte antigen (HLA)-A*0201 þ iPS cells (iPS cell-derived DC (ipDC)), using protocols compliant with their subsequent clinical application. Unlike moDC, a subset of ipDC was found to coexpress CD141 and XCR1 that have been shown previously to define the human equivalent of mouse CD8a þ DC, in which the capacity for cross-presentation has been shown to reside. Accordingly, ipDC were able to cross-present the TAA, Melan A, to a CD8 þ T-cell clone and stimulate primary Melan A-specific responses among naïve T cells from an HLA-A*0201 þ donor. Given that CD141 þ XCR1 þ DC are present in peripheral blood in trace numbers that preclude their clinical application, the ability to generate a potentially unlimited source from iPS cells offers the possibility of harnessing their capacity for cross-priming of cytotoxic T lymphocytes for the induction of tumourspecific immune responses.

Although the rational design of tolerogenic dendritic cells for modulating the outcome of organ transplantation remains ambitious, the use of pharmacological agents to influence their functional phenotype continues to illuminate the basic biology of this critical cell type.

The use of DC to induce antigen-specific tolerance by tapping into the Treg network remains a viable prospect for future strategies for immune intervention in allograft rejection. Furthermore, principles learned from the study of whole organ transplantation may find application in the emerging field of regenerative medicine, in which the use of immune suppression is likely to be contraindicated.