Detection of a Large Novel α-Thalassemia Deletion in an Autochthonous Belgian Family.

α-Thalassemia (α-thal) is a common hemoglobinopathy mainly caused by deletion of one or both α-globin genes. We describe an autochthonous Belgian family diagnosed with α-thal trait. Molecular analysis revealed a novel large deletion of at least 170 kb between 226.68 kb (0.2 Mb) and 402.68 kb (0.4 Mb) from the telomere of 16p, leaving the subtelomeric region intact. The deletion includes both α-globin genes (HBA1 and HBA2) but also flanking genes possibly related to non hematological effects: HBQ1, LUC7L, ITFG3, RGS11, ARHGDIG, PDIA2 and AXIN1. These genes are not contained in the region (0.9 and 1.7 Mb from the telomere of 16p) associated with α-thal intellectual disability (ATR-16) syndrome. However, further research is necessary to exclude other potential effects than α-thal in patients with a large deletion at 0.2-0.4 Mb from the telomere of 16p. Genetic counseling is important for carriers of this deletion as homozygosity for the α-globin (- -/) haplotype may lead to Hb Bart's (γ4) hydrops fetalis syndrome.

Tumor-induced myeloid-derived suppressor cell subsets exert either inhibitory or stimulatory effects on distinct CD8+ T-cell activation events.

Tumor growth coincides with an accumulation of myeloid-derived suppressor cells (MDSCs), which exert immune suppression and which consist of two main subpopulations, known as monocytic (MO) CD11b(+) CD115(+) Ly6G(-) Ly6C(high) MDSCs and granulocytic CD11b(+) CD115(-) Ly6G(+) Ly6C(int) polymorphonuclear (PMN)-MDSCs. However, whether these distinct MDSC subsets hamper all aspects of early CD8(+) T-cell activation--including cytokine production, surface marker expression, survival, and cytotoxicity--is currently unclear. Here, employing an in vitro coculture system, we demonstrate that splenic MDSC subsets suppress antigen-driven CD8(+) T-cell proliferation, but differ in their dependency on IFN-γ, STAT-1, IRF-1, and NO to do so. Moreover, MO-MDSC and PMN-MDSCs diminish IL-2 levels, but only MO-MDSCs affect IL-2Rα (CD25) expression and STAT-5 signaling. Unexpectedly, however, both MDSC populations stimulate IFN-γ production by CD8(+) T cells on a per cell basis, illustrating that some T-cell activation characteristics are actually stimulated by MDSCs. Conversely, MO-MDSCs counteract the activation-induced change in CD44, CD62L, CD162, and granzyme B expression, while promoting CD69 and Fas upregulation. Together, these effects result in an altered CD8(+) T-cell adhesiveness to the extracellular matrix and selectins, sensitivity to FasL-mediated apoptosis, and cytotoxicity. Hence, MDSCs intricately influence different CD8(+) T-cell activation events in vitro, whereby some parameters are suppressed while others are stimulated.

Human multipotent adult progenitor cells are nonimmunogenic and exert potent immunomodulatory effects on alloreactive T-cell responses.

Multipotent adult progenitor cells (MAPCs) are bone marrow-derived nonhematopoietic stem cells with a broad differentiation potential and extensive expansion capacity. A comparative study between human mesenchymal stem cells (hMSCs) and human MAPCs (hMAPCs) has shown that hMAPCs have clearly distinct phenotypical and functional characteristics from hMSCs. In particular, hMAPCs express lower levels of MHC class I than hMSCs and cannot only differentiate into typical mesenchymal cell types but can also differentiate in vitro and in vivo into functional endothelial cells. The use of hMSCs as cellular immunomodulatory stem cell products gained much interest since their immunomodulatory capacities in vitro became evident over the last decade. Currently, the clinical grade stem cell product of hMAPCs is already used in clinical trials to prevent graft-versus-host disease (GVHD), as well as for the treatment of acute myocardial infarct, ischemic stroke, and Crohn's disease. Therefore, we studied the immune phenotype, immunogenicity, and immunosuppressive effect of hMAPCs in vitro. We demonstrated that hMAPCs are nonimmunogenic for T-cell proliferation and cytokine production. In addition, hMAPCs exert strong immunosuppressive effects on T-cell alloreactivity and on T-cell proliferation induced by mitogens and recall antigens. This immunomodulatory effect was not MHC restricted, which makes off-the-shelf use promising. The immunosuppressive effect of hMAPCs is partially mediated via soluble factors and dependent on indoleamine 2,3-dioxygenase (IDO) activity. At last, we isolated hMAPCs, the clinical grade stem cell product of hMAPCs, named MultiStem, and hMSCs from one single donor and observed that both the immunogenicity and the immunosuppressive capacities of all three stem cell products are comparable in vitro. In conclusion, hMAPCs have potent immunomodulatory properties in vitro and can serve as a valuable cell source for the clinical use of immunomodulatory cellular stem cell product.

G-CSF stem cell mobilization in human donors induces polymorphonuclear and mononuclear myeloid-derived suppressor cells.

The role of myeloid-derived suppressor cells (MDSC) is emerging in transplantation. An expansion of myeloid progenitor cells with suppressive capacity has been reported to occur as a bystander phenomenon in the course of allogeneic hematopoietic stem cell transplantation (allo-HSCT) protocols, particularly, in mice during bone marrow chimerism induction and in human stem cell donors during G-CSF-mobilization protocols. Hypothesizing that such 'regulatory myeloid cells' play a role in regulating post-transplant T-cell alloreactivity, we performed a phenotypical and functional characterization of these cells in peripheral blood stem cell grafts of G-CSF-treated donors. We demonstrate that expanding myeloid cells in the peripheral blood of G-CSF-mobilized donors comprise the typical phenotype of the mononuclear and polymorphonuclear MDSC-subtypes that were recently described in cancer patients, and that both MDSC-subsets have the capacity to regulate alloreactive T-cell responses in-vitro. This study provides the basis for investigating the clinical relevance of MDSC and MDSC-subtypes in human allo-HSCT.

Oct4-negative multipotent adult progenitor cells and mesenchymal stem cells as regulators of T-cell alloreactivity in mice.

Multipotent adult progenitor cells (MAPC) are clinically being explored as an alternative to mesenchymal stem cells (MSC) for the immunomodulatory control of graft-versus-host disease (GvHD). Here, we performed an explorative study of the immunomodulatory potential of mouse MAPC (mMAPC), in comparison with that of MSC (mMSC) using experimental models of T-cell alloreactivity. Suppressive effects of Oct4-expressing mMAPC have been described previously; here, we studied mMAPC expressing low to no Oct4 ('mClone-3'), recently shown to be most representative for the human MAPC counterpart. mClone-3 and mMSC exhibited similar immunophenotype and in vitro immunogenic behavior. Allogeneic T-cell↔dendritic cell-proliferation assays showed strong dose-dependent T-cell-suppressive effects of both mClone-3 and mMSC. In a popliteal lymph node assay, mClone-3 and mMSC equally suppressed in vivo alloreactive T-cell expansion. We conclude that mouse MAPC and MSC exhibit similar immunosuppressive behavior in in vitro and local in vivo GvHD assays.