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Functional differences and cell collaboration between murine lymphoid dendritic cells (DC) and macrophages (MØ) in antigen presentation for T-cell activation were analysed with splenic DC and MØ, culture-derived bone-marrow (BM)-MØ, and DC-like and MØ-like cell lines. DC were the best stimulators of allogeneic mixed leucocyte reaction (MLR), but splenic MØ and small activated BM-MØ were almost as effective. In contrast to MLR stimulation, small activated BM-MØ were the most effective antigen-presenting cells (APC) for the presentation of whole Corynebacterium parvum (CP) organisms, possibly by virtue of their phagocytic and lysosomal functions, which could be particularly important for processing particulate antigens. Large activated BM-MØ were ineffective in stimulating MLR and CP-specific T-cell proliferation. The functional differences between BM-MØ subsets could not be explained by failure to express surface la or to take up antigen. Non-phagocytic APC, such as DC and the DC-like line P388AD.4, had low presenting activity for CP and were much less effective at presenting glutaraldehyde-fixed CP than MØ. This suggests that DC are dependent on the shedding of soluble antigen (reduced by glutaraldehyde fixation) from the bacteria, and they may also be less efficient than MØ at processing the fixed bacteria. The la- MØ-like line, P388D1, was devoid of APC activity, but could greatly enhance P388AD.4-induced T-cell proliferation to whole bacterial organisms. Similarly, co-culture of splenic DC and MØ produced very pronounced synergistic effects in proliferative responses to CP and keyhole limpet haemocyanin. The function of MØ in this partnership was sensitive to chloroquine and could not be replaced by MØ culture fluids or recombinant interleukin-1. Thus, MØ may contribute processed antigen in a form more suitable for presentation by DC. These results provide a rationale for the functional dichotomy between DC and MØ. [ABSTRACT FROM AUTHOR]

Historically, our understanding of mechanisms underlying human leukemogenesis are inferred from genetically engineered mouse models. Relatively, few models that use primary human cells recapitulate the full leukemic transformation as assayed in xenografts and myeloid transformation is infrequent. We report a humanized experimental leukemia model where xenografts develop aggressive acute myeloid leukemia (AML) with disseminated myeloid sarcomas within 4 weeks following transplantation of cord blood transduced with vectors expressing BCR-ABL1 and a dominant-negative isoform of IKAROS, Ik6. Ik6 induced transcriptional programs in BCR-ABL1-transduced progenitors that contained repressed B-cell progenitor programs, along with strong stemness, proliferation and granulocyte-monocytic progenitor (GMP) signatures-a novel combination not induced in control groups. Thus, wild-type IKAROS restrains stemness properties and has tumor suppressor activity in BCR-ABL1-initiated leukemia. Although IKAROS mutations/deletions are common in lymphoid transformation, they are found also at low frequency in AML that progress from a prior myeloproliferative neoplasm (MPN) state. Our experimental system provides an excellent model to gain insight into these rare cases of AML transformation and the properties conferred by IKAROS loss of function as a secondary mutation. More generally, our data points to the importance of deregulated stemness/lineage commitment programs in human myeloid leukemogenesis. [ABSTRACT FROM AUTHOR]

Historically, our understanding of mechanisms underlying human leukemogenesis are inferred from genetically engineered mouse models. Relatively, few models that use primary human cells recapitulate the full leukemic transformation as assayed in xenografts and myeloid transformation is infrequent. We report a humanized experimental leukemia model where xenografts develop aggressive acute myeloid leukemia (AML) with disseminated myeloid sarcomas within 4 weeks following transplantation of cord blood transduced with vectors expressing BCR-ABL1 and a dominant-negative isoform of IKAROS, Ik6. Ik6 induced transcriptional programs in BCR-ABL1-transduced progenitors that contained repressed B-cell progenitor programs, along with strong stemness, proliferation and granulocyte-monocytic progenitor (GMP) signatures-a novel combination not induced in control groups. Thus, wild-type IKAROS restrains stemness properties and has tumor suppressor activity in BCR-ABL1-initiated leukemia. Although IKAROS mutations/deletions are common in lymphoid transformation, they are found also at low frequency in AML that progress from a prior myeloproliferative neoplasm (MPN) state. Our experimental system provides an excellent model to gain insight into these rare cases of AML transformation and the properties conferred by IKAROS loss of function as a secondary mutation. More generally, our data points to the importance of deregulated stemness/lineage commitment programs in human myeloid leukemogenesis. [ABSTRACT FROM AUTHOR]

Purpose We have applied cutting-edge mass cytometry (MC) technology to serial bronchoalveolar lavage (BAL) cells obtained from lung transplant recipients (LTRs) and have used it to compare the cellular composition of the BAL compartment in patients who remain stable or go on to develop lung allograft dysfunction (LAD), defined here as a drop, from any cause, in the forced expiratory volume in 1 second of 20% from the best post-transplant baseline value. Methods We have collected and cryopreserved BAL cells from 50 consecutive LTRs at their 3-, 6- and 9-month post-transplant surveillance bronchoscopies. Cryopreserved samples were then recovered and labeled with a panel of 37 heavy metal-tagged antibodies against surface markers and intracellular cytokines before MC. We applied t-distributed stochastic neighbor embedding (tSNE; Fig1 A) which assists with better visualization of multi-dimensinal analysis to identify both common and rare cell populations in the BAL. We further applied an algorithm called cluster identification, characterization and regression (CITRUS; Fig1 B) to allow unsupervised identification of differentially represented BAL cellular subsets between stable and LAD patients. Results Longitudinal analysis of the first 25 patients demonstrated different cell subsets and cytokine-producing cells, with substantial intra- and inter-patient variation. Our data identified an elevation in the frequency of CD4+ CD57+ PD-1+ cells separates LAD (18.41±4.89%) from stable patients (4.43±2.11%; Fig1 C). Emergence of CD57+ PD-1+ events among CD4+ T cells preceded LAD by up to several weeks (Fig1 D), suggesting that these cells may contribute to LAD development rather than simply correlating with it. Conclusion Our data suggest that emergence of CD4+ CD57+ PD-1+ T cells may predict and/or contribute to allograft dysfunction. Molecular and functional studies on this cell population are underway to obtain a better understanding of their role in lung transplant immunobiology. [ABSTRACT FROM AUTHOR]