Subpopulations of T Regulatory Cells in Blood Stem Cell Harvests Influence Development of Acute Graft Versus Host Disease in Allogeneic Transplant Recipients.

BACKGROUND: CD4+ FoxP3+ regulatory T cells (Tregs) are the potent suppressors of activation and proliferation of conventional T cells. Tregs subdivided by their expression of FoxP3 and CD45RA identify clinically important functional subsets. METHODS: We analyzed Treg subpopulations in hematopoietic stem cell harvests (SCH) from 22 allogeneic (matched unrelated and sibling) donors with flow cytometry by their expression of CD45RA, CD127, CD25, and FoxP3 marker combinations. RESULTS: A high fraction of "activated Tregs", defined as CD4+ FoxP3hi CD45RAlo (aTreg) cells relative to all CD4+ T-cells, in the SCH correlated with no subsequent development of acute graft-versus-host disease (aGVHD) in the corresponding transplant recipients (aTreg 1.29%, range 0.96-1.64%, vs. 0.23%, range 0.14-0.56%, with subsequent aGvHD; P = 0.0015). The "non-Treg" cells, defined by CD4+ FoxP3med/lo CD45RAlo , and resting Treg (rTreg) cells, defined by CD4+ FoxP3med CD45RAhi , did not correlate with aGvHD development. We also showed that phenotypic aTregs could be induced in vitro from nonTregs under homeostatic proliferation conditions and that this ability correlated with the CD127 and CD25 expression patterns. CONCLUSIONS: We identified a subset of T CD4+ FoxP3+ cells, i.e., aTregs that were correlated to aGvHD development, and demonstrated plasticity of the nonTreg population to provide phenotypic aTregs. This could have both a predictive clinical relevance in inflammatory conditions as well as support a rationale for development of cell targeted therapy. © 2016 International Clinical Cytometry Society.

Single-cell molecular analysis defines therapy response and immunophenotype of stem cell subpopulations in CML.

Understanding leukemia heterogeneity is critical for the development of curative treatments as the failure to eliminate therapy-persistent leukemic stem cells (LSCs) may result in disease relapse. Here we have combined high-throughput immunophenotypic screens with large-scale single-cell gene expression analysis to define the heterogeneity within the LSC population in chronic phase chronic myeloid leukemia (CML) patients at diagnosis and following conventional tyrosine kinase inhibitor (TKI) treatment. Our results reveal substantial heterogeneity within the putative LSC population in CML at diagnosis and demonstrate differences in response to subsequent TKI treatment between distinct subpopulations. Importantly, LSC subpopulations with myeloid and proliferative molecular signatures are proportionally reduced at a higher extent in response to TKI therapy compared with subfractions displaying primitive and quiescent signatures. Additionally, cell surface expression of the CML stem cell markers CD25, CD26, and IL1RAP is high in all subpopulations at diagnosis but downregulated and unevenly distributed across subpopulations in response to TKI treatment. The most TKI-insensitive cells of the LSC compartment can be captured within the CD45RA- fraction and further defined as positive for CD26 in combination with an aberrant lack of cKIT expression. Together, our results expose a considerable heterogeneity of the CML stem cell population and propose a Lin-CD34+CD38-/lowCD45RA-cKIT-CD26+ population as a potential therapeutic target for improved therapy response.

CD133 is not present on neurogenic astrocytes in the adult subventricular zone, but on embryonic neural stem cells, ependymal cells, and glioblastoma cells.

Human brain tumor stem cells have been enriched using antibodies against the surface protein CD133. An antibody recognizing CD133 also served to isolate normal neural stem cells from fetal human brain, suggesting a possible lineage relationship between normal neural and brain tumor stem cells. Whether CD133-positive brain tumor stem cells can be derived from CD133-positive neural stem or progenitor cells still requires direct experimental evidence, and an important step toward such investigations is the identification and characterization of normal CD133-presenting cells in neurogenic regions of the embryonic and adult brain. Here, we present evidence that CD133 is a marker for embryonic neural stem cells, an intermediate radial glial/ependymal cell type in the early postnatal stage, and for ependymal cells in the adult brain, but not for neurogenic astrocytes in the adult subventricular zone. Our findings suggest two principal possibilities for the origin of brain tumor stem cells: a derivation from CD133-expressing cells, which are normally not present in the adult brain (embryonic neural stem cells and an early postnatal intermediate radial glial/ependymal cell type), or from CD133-positive ependymal cells in the adult brain, which are, however, generally regarded as postmitotic. Alternatively, brain tumor stem cells could be derived from proliferative but CD133-negative neurogenic astrocytes in the adult brain. In the latter case, brain tumor development would involve the production of CD133.