FoxP3 is a key transcription factor for the development and function of natural CD4(+) regulatory T cells (Treg cells). Here we show that human FoxP3(+)CD4(+) T cells were composed of three phenotypically and functionally distinct subpopulations: CD45RA(+)FoxP3(lo) resting Treg cells (rTreg cells) and CD45RA(-)FoxP3(hi) activated Treg cells (aTreg cells), both of which were suppressive in vitro, and cytokine-secreting CD45RA(-)FoxP3(lo) nonsuppressive T cells. The proportion of the three subpopulations differed between cord blood, aged individuals, and patients with immunological diseases. Terminally differentiated aTreg cells rapidly died whereas rTreg cells proliferated and converted into aTreg cells in vitro and in vivo. This was shown by the transfer of rTreg cells into NOD-scid-common gamma-chain-deficient mice and by TCR sequence-based T cell clonotype tracing in peripheral blood in a normal individual. Taken together, the dissection of FoxP3(+) cells into subsets enables one to analyze Treg cell differentiation dynamics and interactions in normal and disease states, and to control immune responses through manipulating particular FoxP3(+) subpopulations.

To establish a more appropriate animal recipient for xenotransplantation, NOD/ SCID/␥ c null mice double homozygous for the severe combined immunodeficiency (SCID) mutation and interleukin-2R␥ (IL-2R␥) allelic mutation (␥ c null ) were generated by 8 backcross matings of C57BL/6J-␥ c null mice and NOD/Shi-scid mice. When human CD34 ؉ cells from umbilical cord blood were transplanted into this strain, the engraftment rate in the peripheral circulation, spleen, and bone marrow were significantly higher than that in NOD/Shiscid mice treated with anti-asialo GM1 antibody or in the ␤2-microglobulindeficient NOD/LtSz-scid (NOD/SCID/ ␤2m null ) mice, which were as completely defective in NK cell activity as NOD/SCID/ ␥ c null mice. The same high engraftment rate of human mature cells was observed in ascites when peripheral blood mononuclear cells were intraperitoneally transferred. In addition to the high engraftment rate, multilineage cell differentiation was also observed.

We found adult human stem cells that can generate, from a single cell, cells with the characteristics of the three germ layers. The cells are stress-tolerant and can be isolated from cultured skin fibroblasts or bone marrow stromal cells, or directly from bone marrow aspirates. These cells can self-renew; form characteristic cell clusters in suspension culture that express a set of genes associated with pluripotency; and can differentiate into endodermal, ectodermal, and mesodermal cells both in vitro and in vivo. When transplanted into immunodeficient mice by local or i.v. injection, the cells integrated into damaged skin, muscle, or liver and differentiated into cytokeratin 14-, dystrophin-, or albumin-positive cells in the respective tissues. Furthermore, they can be efficiently isolated as SSEA-3(+) cells. Unlike authentic ES cells, their proliferation activity is not very high and they do not form teratomas in immunodeficient mouse testes. Thus, nontumorigenic stem cells with the ability to generate the multiple cell types of the three germ layers can be obtained through easily accessible adult human mesenchymal cells without introducing exogenous genes. These unique cells will be beneficial for cell-based therapy and biomedical research.

Although germline cells can form multipotential embryonic stem (ES)/embryonic germ (EG) cells, these cells can be derived only from embryonic tissues, and such multipotent cells have not been available from neonatal gonads. Here we report the successful establishment of ES-like cells from neonatal mouse testis. These ES-like cells were phenotypically similar to ES/EG cells except in their genomic imprinting pattern. They differentiated into various types of somatic cells in vitro under conditions used to induce the differentiation of ES cells and produced teratomas after inoculation into mice. Furthermore, these ES-like cells formed germline chimeras when injected into blastocysts. Thus, the capacity to form multipotent cells persists in neonatal testis. The ability to derive multipotential stem cells from the neonatal testis has important implications for germ cell biology and opens the possibility of using these cells for biotechnology and medicine.

Oligomeric forms of amyloid-β peptide (Aβ) are thought to play a pivotal role in the pathogenesis of Alzheimer's disease (AD), but the mechanism involved is still unclear. Here, we generated induced pluripotent stem cells (iPSCs) from familial and sporadic AD patients and differentiated them into neural cells. Aβ oligomers accumulated in iPSC-derived neurons and astrocytes in cells from patients with a familial amyloid precursor protein (APP)-E693Δ mutation and sporadic AD, leading to endoplasmic reticulum (ER) and oxidative stress. The accumulated Aβ oligomers were not proteolytically resistant, and docosahexaenoic acid (DHA) treatment alleviated the stress responses in the AD neural cells. Differential manifestation of ER stress and DHA responsiveness may help explain variable clinical results obtained with the use of DHA treatment and suggests that DHA may in fact be effective for a subset of patients. It also illustrates how patient-specific iPSCs can be useful for analyzing AD pathogenesis and evaluating drugs.