Adipocytes are part of hematopoietic microenvironment, even though up to now in humans, their role in hematopoiesis is still questioned. We have previously shown that accumulation of fat cells in femoral bone marrow (BM) coincides with increased expression of neuropilin-1 (NP-1), while it is weakly expressed in hematopoietic iliac crest BM. Starting from this observation, we postulated that adipocytes might exert a negative effect on hematopoiesis mediated through NP-1. To test this hypothesis, we set up BM adipocytes differentiated into fibroblast-like fat cells (FLFC), which share the major characteristics of primitive unilocular fat cells, as an experimental model. As expected, FLFCs constitutively produced macrophage colony stimulating factor and induced CD34 ؉ differentiation into macrophages independently of cell-to-cell contact. By contrast, granulopoiesis was hampered by cellto-cell contact but could be restored in transwell culture conditions, together with granulocyte colony stimulating factor production. Both functions were also recovered when FLFCs cultured in contact with CD34 ؉ cells were treated with an antibody neutralizing NP-1, which proved its critical implication in contact inhibition. An inflammatory cytokine such as interleukin-1 ␤ or dexamethasone modulates FLFC properties to restore granulopoiesis. Our data provide the first evidence that primary adipocytes exert regulatory functions during hematopoiesis that might be implicated in some pathological processes. STEM CELLS

It has been shown that γδ T cells protect against the formation of squamous cell carcinoma (SCC) in several models. However, the role of γδ T cells in human papillomavirus (HPV)-associated uterine cervical SCC, the third-leading cause of death by cancer in women, is unknown. Here, we investigated the impact of γδ T cells in a transgenic mouse model of carcinogenesis induced by HPV16 oncoproteins. Surprisingly, γδ T cells promoted the development of HPV16 oncoprotein-induced lesions. HPV16 oncoproteins induced a decrease in epidermal Skint1 expression and the associated antitumor Vγ5 γδ T cells, which were replaced by γδ T-cell subsets (mainly Vγ6 γδCCR2CCR6) actively producing IL-17A. Consistent with a proangiogenic role, γδ T cells promoted the formation of blood vessels in the dermis underlying the HPV-induced lesions. In human cervical biopsies, IL-17A γδ T cells could only be observed at the cancer stage (SCC), where HPV oncoproteins are highly expressed, supporting the clinical relevance of our observations in mice. Overall, our results suggest that HPV16 oncoproteins induce a reorganization of the local epithelial-associated γδ T-cell subpopulations, thereby promoting angiogenesis and cancer development.

Expression of a self peptide derived from the alpha chain of MHC class II (I-Ed) in association with I-Ab was studied in the murine thymic microenvironment. Previous work using the mAb Y-Ae which specifically recognizes the E alpha-I-Ab complex had reported differential expression between the thymic medulla and the cortex of this peptide-MHC complex: MHC class II-positive stromal cells in the medulla were strongly positive, whereas this complex was barely detectable on cortical epithelial cells (cEpC) in situ. This difference in presentation of an abundant self peptide is intriguing, since the self protein from which this peptide is derived and the presenting MHC molecule are strongly expressed in both compartments. In this report we show by cell surface phenotype and functional assays that isolated cEpC express the E alpha-I-Ab complex at significant although lower levels than medullary dendritic cells (DC), when examined ex vivo. These results support the notion that cEpC and bone marrow-derived stromal cells present a similar set of self peptide-MHC complexes in situ. In addition, we detect intercellular transfer in situ of the E alpha determinant from radioresistant stromal cells to thymic DC, a mechanism which may enhance the efficacy of tolerance induction by spreading self antigens with the thymic microenvironment.

Different retrospective studies have shown that microvessel counting (MVC) is an independent prognostic marker for clinical outcome in breast cancer. The aim of this study was to evaluate the prognostic value of MVC alone or in association with classical clinicopathological parameters, as well as the reproducibility of the technique. We analyzed a retrospective series of 216 cases of breast carcinoma. Tissue sections were stained for Factor-VIII-related antigen. Microvessel quantification was performed at x400 magnification in the three most vascular areas of the tumors (hot spots). Mean and highest values were studied. Furthermore, a semi-quantitative evaluation of MVC was performed by use of an image-analysis system. The effect of multiple factors on survival was tested under a Cox multivariate proportional hazards model. In ten cases, a study of the reproducibility was done by evaluating MVC in different sections of the same block and in different blocks of a same tumor. There was no association between MVC (determined at a microscopic level or by image analysis) and overall survival or relapse-free survival. No association was found with tumor size, tumor grade, and lymph-node status. The study of reproducibility showed a very high intra-tumoral variation of MVC. The intra-individual coefficient of variation (CV) varied between 20 and 80%. This study did not show any significant correlation between angiogenesis, as assessed by MVC, and relapse-free survival or overall survival in infiltrating breast carcinomas. The low reproducibility of the MVC for the same tumors suggests that this technique must still be optimized before routine application.