Luciana Marti

Absolute Values of Dendritic Cell Subsets in Bone Marrow, Cord Blood, and Peripheral Blood Enumerated by a Novel Method

Dendritic cells (DCs) are pivotal in inducing immunity or alternatively downregulating immune reactivity. In humans, the opposing phenotypic subsets of CD11c+/CD123− “myeloid” DCs and CD123+/CD11c− “lymphoid” DCs have been proposed to orchestrate these immune responses. In this study we determined the absolute numbers of both subsets in three resting hematopoietic tissues by employing a novel flow cytometry method, eliminating processing steps and calculations based on mononuclear cell percentages. Internal bead standards along with the cells of interest were simultaneously acquired directly from unmanipulated whole blood specimens. We found significant differences (p < 0.001) between the mean absolute numbers of CD123+/CD11c− lymphoid DCs among the three sources, with the fewest present in peripheral blood (8.2/μl), about 50% more in cord blood (12.2/μl), and fivefold more in bone marrow (40.2/μl). Cord blood and bone marrow CD11c+/CD123− myeloid DC counts did not differ from each other (23.5/μl and 28.9/μl, respectively) but peripheral blood contained significantly fewer (15.5/μl, p = 0.006). CD11c+/CD123− DCs had significantly higher surface expression of HLA‐DR (p < 0.001) in all three sources. To test for association with the DC subsets, T, B, and natural killer (NK) lymphocytes were also enumerated. In bone marrow only, significant correlations were found between the size of the CD123+/CD11c− lymphoid DC pool and NK cells (p = 0.0029) and B cells (p = 0.0033). These data support the hypothesis that a common CD123+/CD11c− DC, NK cell, and B cell progenitor is resident in marrow, and this cell may be identical to the common lymphoid progenitor previously described in mice and/or the human CD34+/Lin−/CD10+ progenitor.

Interleukin-7 Permits Th1/Tc1 Maturation and Promotes Ex vivo Expansion of Cord Blood T Cells: A Critical Step toward Adoptive Immunotherapy after Cord Blood Transplantation

Donor leukocyte infusions (DLI) in the allogeneic hematopoietic transplant setting can provide a clinically relevant boost of immunity to reduce opportunistic infections and to increase graft-versus-leukemia activity. Despite significant advances in applicability, DLI has not been available for single-unit recipients of unrelated cord blood transplant. Ex vivo expansion of cord blood T cells can be achieved with interleukin (IL)-2 and CD3/CD28 costimulatory beads. However, significant apoptosis occurs in proliferating T cells, diminishing the yield and skewing the CD4/CD8 ratio in the T-cell population, jeopardizing the potential efficacy of DLI. In this study, we show that interleukin (IL)-7 not only reduces apoptosis of activated T lymphocytes and enhances their proliferation but also promotes functional maturation, leading to secretion of IFN-gamma and other key cytokines. Recognizing that infused T lymphocytes will need to meet microbial antigens in secondary lymphoid organs to generate effectors, we also show that expansion with IL-7 promotes the preservation of a polyclonal broad T-cell receptor repertoire and a surface phenotype that favors lymph node homing. Expanded lymphocytes lack alloreactivity against recipient and other allogeneic cells, indicating a favorable safety profile from graft-versus-host disease. Nevertheless, expanded T cells can be primed subsequently against lymphoid and myeloid leukemia cells to generate tumor-specific cytotoxic T cells. Taken together, our findings offer a major step in fulfilling critical numerical and biological requirements to quickly generate a DLI product ex vivo using a negligible fraction of a cord blood graft that provides a flexible adoptive immunotherapy platform for both children and adults.

A novel mechanism of NPM1 cytoplasmic localization in acute myeloid leukemia: the recurrent gene fusion NPM1–HAUS1

NPM1 heterozygous mutations are present in roughly a third of patients with acute myeloid leukemia (AML), making it one of the most frequent genomic alterations in these patients.[1][1] The mutations are characterized by frameshift insertions in the region encoding the C-terminus of the protein,