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Lymphoid-tissue dendritic cells ( DCs) are short-lived and need to be continuously replenished from bone marrow-derived DC progenitor cells. Fms-related tyrosine kinase 3 is expressed during cellular development from hematopoietic progenitors to lymphoid-tissue DCs. Fms-related tyrosine kinase 3 ligand ( Flt3L) is an essential, nonredundant cytokine for DC progenitor to lymphoid tissue DC differentiation and maintenance. However, which cells contribute to Flt3L production and how Flt3L cytokine levels are regulated in steady state and during immune reactions remains to be determined. Here we demonstrate that besides nonhematopoietic cells, WT T cells produce Flt3 L and contribute to the generation of both classical DCs (c DCs) and plasmacytoid DCs in Flt3 L−/− mice. Upon stimulation in vitro, CD4+ T cells produce more Flt3 L than CD8+ T cells. Moreover, in vivo stimulation of naïve OT- II CD4+ T cells with OVA leads to increase of pre-c DCs and c DCs in draining lymph nodes of Flt3 L−/− mice in a partially Flt3 L-dependent manner. Thus, Flt3 L-mediated lymphoid tissue DC homeostasis is regulated by steady-state T cells as well as by proliferative T cells, fostering local development of lymphoid organ resident DCs. [ABSTRACT FROM AUTHOR]

Summary. Inositol hexaphosphate (IP6 ), a naturally polyphosphorylated carbohydrate, has been reported to have significant in vivo and in vitr o anticancer activity against numerous tumours, such as colon, prostate, breast, liver and rhabdomyosarcomas. To confirm this activity in haematological malignancies and to characterize some of the mechanisms of IP6 action, we analysed its effects on human leukaemic cell lines and fresh chronic myelogenous leukaemia (CML) progenitor cells using a combined cellular and molecular approach. IP6 had a dose-dependent cytotoxic effect on all of the evaluated cell lines, with accumulation in the G2 M phase in two out of five cell lines tested. At the molecular level, cDNA microarray analysis after IP6 exposure showed an extensive downmodulation of genes involved in transcription and cell cycle regulation and a coherent upregulation of cell cycle inhibitors. Furthermore, IP6 treatment of fresh leukaemic samples of bone marrow CD34+ CML progenitor cells significantly inhibited granulocyte–macrophage colony-forming unit (CFU-GM) formation (P = 0·0062) in comparison to normal bone marrow specimens, which were not affected. No differentiating effect on HL60 cells was observed. Taken together, our results confirm the antiproliferative activity of IP6 and suggest that it may have a specific antitumour effect also in chronic myeloid leukaemias, via active gene modulation. [ABSTRACT FROM AUTHOR]

Background: Tolerance‐inducing approaches to xenotransplantation would be optimal and may be necessary for long‐term survival of transplanted pig organs in human patients. The ideal approach would generate donor‐specific unresponsiveness to the pig organ without suppressing the patient's normal immune function. Porcine thymus transplantation has shown efficacy in promoting xenotolerance in humanized mice and large animal models. However, murine studies demonstrate that T cells selected in a swine thymus are positively selected only by swine thymic epithelial cells, and therefore, cells expressing human HLA‐restricted TCRs may not be selected efficiently in a transplanted pig thymus. This may lead to suboptimal patient immune function. Methods: To assess human thymocyte selection in a pig thymus, we used a TCR transgenic humanized mouse model to study positive selection of cells expressing the MART1 TCR, a well‐characterized human HLA‐A2‐restricted TCR, in a grafted pig thymus. Results: Positive selection of T cells expressing the MART1 TCR was inefficient in both a non‐selecting human HLA‐A2– or swine thymus compared with an HLA‐A2+ thymus. Additionally, CD8 MART1 TCRbright T cells were detected in the spleens of mice transplanted with HLA‐A2+ thymi but were significantly reduced in the spleens of mice transplanted with swine or HLA‐A2– thymi. [Correction added on October 15, 2019, after first online publication: The missing superscript values +, –, and bright have been included in the Results section.] Conclusions: Positive selection of cells expressing a human‐restricted TCR in a transplanted pig thymus is inefficient, suggesting that modifications to improve positive selection of cells expressing human‐restricted TCRs in a pig thymus may be necessary to support development of a protective human T‐cell pool in future patients. [ABSTRACT FROM AUTHOR]

Objective: Vascular abnormalities represent the main component of the pathobiology of systemic sclerosis (SSc), progressing from structural derangements of the microcirculation with abortive neoangiogenesis to final vessel loss. Since circulating endothelial progenitor cells (EPCs) are important in the vascular repair process, we undertook this study to examine their numbers in the peripheral blood (PB) of SSc patients and to evaluate whether their status is related to impaired quantitative and/or qualitative aspects of the bone marrow (BM) microenvironment., Methods: Circulating EPCs from 62 SSc patients were evaluated by flow cytometry and characterized as CD45 negative and CD133 positive. BM EPCs, identified as CD133 positive, were isolated from 14 SSc patients and grown to induce endothelial differentiation. In addition, progenitor numbers and functional properties of hematopoietic and stromal compartments were analyzed by various assays., Results: We found that EPCs were detectable in the PB of patients with SSc, and their number was significantly increased in patients with early-stage disease but not in those with late-stage disease. All of the examined BM samples contained reduced numbers of EPCs and stromal cells, both of which were functionally impaired. Both endothelial and stromal progenitors expressed vascular endothelial growth factor receptor, indicating that BM is strongly induced to differentiate into the endothelial lineage; furthermore, only BM EPCs from patients with early disease led to endothelial differentiation in vitro., Conclusion: This study provides the first demonstration that in SSc, there is a complex impairment in the BM microenvironment involving both the endothelial and mesenchymal stem cell compartments and that this impairment might play a role in defective vasculogenesis in scleroderma.

Inositol hexaphosphate (IP(6)), a naturally polyphosphorylated carbohydrate, has been reported to have significant in vivo and in vitro anticancer activity against numerous tumours, such as colon, prostate, breast, liver and rhabdomyosarcomas. To confirm this activity in haematological malignancies and to characterize some of the mechanisms of IP(6) action, we analysed its effects on human leukaemic cell lines and fresh chronic myelogenous leukaemia (CML) progenitor cells using a combined cellular and molecular approach. IP(6) had a dose-dependent cytotoxic effect on all of the evaluated cell lines, with accumulation in the G2M phase in two out of five cell lines tested. At the molecular level, cDNA microarray analysis after IP(6) exposure showed an extensive downmodulation of genes involved in transcription and cell cycle regulation and a coherent upregulation of cell cycle inhibitors. Furthermore, IP(6) treatment of fresh leukaemic samples of bone marrow CD34+ CML progenitor cells significantly inhibited granulocyte-macrophage colony-forming unit (CFU-GM) formation (P = 0.0062) in comparison to normal bone marrow specimens, which were not affected. No differentiating effect on HL60 cells was observed. Taken together, our results confirm the antiproliferative activity of IP(6) and suggest that it may have a specific antitumour effect also in chronic myeloid leukaemias, via active gene modulation.