Regulation of adaptive immunity by innate immune cells is widely accepted. Conversely, adaptive immune cells can also regulate cells of the innate immune system. Here, we report for the first time the essential role of B cells in regulating macrophage (M/) phenotype. In vitro B cell/M/ co-culture experiments together with experiments in transgenic mice models for B-cell deficiency or overexpression showed B1 cells to polarize M/ to a distinct phenotype. This was characterized by downregulated TNF-a, IL-1b and CCL3, but upregulated IL-10 upon LPS stimulation; constitutive expression of M2 M/ markers (e.g. Ym1, Fizz1) and overexpression of TRIF-dependent cytokines (IFN-b, CCL5). Mechanistically, this phenotype was linked to a defective NF-jB activation, but a functional TRIF/STAT1 pathway. B1-cell-derived IL-10 was found to be instrumental in the polarization of these M/. Finally, in vivo relevance of B1-cell-induced M/ polarization was confirmed using the B16 melanoma tumor model where adoptive transfer of B1 cells induced an M2 polarization of tumor-associated M/. Collectively, our results define a new mechanism of M/ polarization wherein B1 cells play a key role in driving M/ to a unique, but M2-biased phenotype. Future studies along these lines may lead to targeting of B1 cells to regulate M/ response in inflammation and cancer. Supporting Information available online IntroductionMacrophages (Mf) are a heterogeneous cell population involved in diverse physiological processes including anti-microbial defence, wound resolution, inflammation, tissue remodeling, plaque formation in atherosclerosis and promotion of tumor growth [1][2][3][4][5][6][7]. Despite their heterogeneity, Mf can be broadly divided into M1 (classically activated) or M2 (alternatively activated) phenotypes [1,[8][9][10][11][12]. The M1 phenotype is induced in response to microbial products such as LPS or proinflammatory cytokines including IFN-g, IL-1b or TNF-a. M1 Mf produce further proinflammatory cytokines (TNF-a, IL-12 and CCL3) with reactive oxygen and nitrogen intermediates, which combine to give M1 Mf potent antimicrobial, tumoricidal and inflammatory properties [12]. In contrast, the M2 phenotype results from exposure to antiinflammatory molecules such as glucocorticoid hormones, IL-4, Ã These authors contributed equally to this work. 2296IL-13, IL-10 or immune complexes [10][11][12]. M2 Mf are antiinflammatory and immunosuppressive in nature. They are highly phagocytic, preferentially activate the arginase pathway, promote angiogenesis, tissue remodeling and have pro-tumoral activity [8,12]. However, in vivo, the division between M1 and M2 cells may be blurred, with the above phenotypes likely representing two extremes in a continuum of Mf functional states [9,[13][14][15].Transcriptome data demonstrate the existence of distinct polarization phenotypes for Mf associated with specific pathological conditions [4,7,[16][17][18]. Based on this, it is believed that the phenotype of an Mf is a reflection of its immediate microenvironment....

Key events of T and B cell biology are regulated through direct interaction with APC or target cells. Trogocytosis is a process whereby CD4+ T, CD8+ T, and B cells capture their specific membrane-bound Ag through the acquisition of plasma membrane fragments from their cellular targets. With the aim of investigating whether the ability to trigger trogocytosis was a selective property of Ag receptors, we set up an assay that allowed us to test the ability of many different cell surface molecules to trigger trogocytosis. On the basis of the analysis of a series of surface molecules on CD4+ T, CD8+ T, and B cells, we conclude that a set of cell type-specific surface determinants, including but not limited to Ag receptors, do trigger trogocytosis. On T cells, these determinants include components of the TCR/CD3 as well as that of coreceptors and of several costimulatory molecules. On B cells, we identified only the BCR and MHC molecules as potentials triggers of trogocytosis. Remarkably, latrunculin, which prevents actin polymerization, impaired trogocytosis by T cells, but not by B cells. This was true even when the same Abs were used to trigger trogocytosis in T or B cells. Altogether, our results indicate that although trogocytosis is performed by all hemopoietic cells tested thus far, both the receptors and the mechanisms involved can differ depending on the lineage of the cell acquiring membrane materials from other cells. This could therefore account for the different biological consequences of Ag capture via trogocytosis proposed for different types of cells.

Detection, quantification, separation and characterization of T and B cells reactive to specific antigens are important tasks in both basic and clinical immunology. Here, we describe an approach allowing the performance of all four tasks on a functional basis by flow cytometry. The assay is based on the property of lymphocytes to capture membrane components from the cells they interact with, in a process we call trogocytosis. Working with CD8 + CTL and target cells labeled with membrane markers, we describe the conditions allowing reactive lymphocytes to be detected rapidly and inexpensively within mixed populations. Accordingly, we used this method to monitor the CTL response triggered in mice after vaccination. In addition, we documented the applicability of this method to the detection of antigen-specific CD4 + T and B cells. While our method is, for the time being, not as sensitive as staining of CTL with MHC class I multimers, it allows the simultaneous quantitative identification of reactive CD8 + , CD4 + and B cells. Altogether, our method offers a simple and general alternative to other methods previously described to detect and quantify lymphocyte reactivity, and it can also be used in combination with those.

We have developed a method exploiting the phenomenon of trogocytosis to detect lymphocytes reacting specifically with target cells by flow cytometry. Trogocytosis is a process by which lymphocytes capture fragments of the plasma membrane from the antigen-presenting cells (APCs) expressing their cognate antigen. For this method, a label (such as a fluorescent lipid or biotin) is first incorporated in the membrane of APCs. These labeled cells are then co-cultured for a few hours with a population of cells containing the lymphocytes to be detected. After this period of stimulation, lymphocytes that have performed trogocytosis are identified by their acquisition of the label initially present on the APC membrane using flow cytometry. A major advantage of this method is its compatibility with the simultaneous detection of phenotypic and/or functional markers on the lymphocytes. Furthermore, cells can be recovered alive and active after detection of trogocytosis, and are therefore available for further characterization or even conceivably for therapeutic purposes.

Introduction and Purpose. Monitoring solid tumor growth and metastasis in small animals is important for cancer research. Noninvasive techniques make longitudinal studies possible, require fewer animals, and have greater statistical power. Such techniques include FDG positron emission tomography (FDG-PET), magnetic resonance imaging (MRI), and optical imaging, comprising bioluminescence imaging (BLI) and fluorescence imaging (FLI). This study compared the performance and usability of these methods in the context of mouse tumor studies. Methods. B16 tumor-bearing mice (n = 4 for each study) were used to compare practicality, performance for small tumor detection and tumor burden measurement. Using RETAAD mice, which develop spontaneous melanomas, we examined the performance of MRI (n = 6 mice) and FDG-PET (n = 10 mice) for tumor identification. Results. Overall, BLI and FLI were the most practical techniques tested. Both BLI and FDG-PET identified small nonpalpable tumors, whereas MRI and FLI only detected macroscopic, clinically evident tumors. FDG-PET and MRI performed well in the identification of tumors in terms of specificity, sensitivity, and positive predictive value. Conclusion. Each of the four methods has different strengths that must be understood before selecting them for use.

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Malignant transformations are often associated with aberrant glycosylation processes that lead to the expression of new carbohydrate antigens at the surface of tumor cells. Of these carbohydrate antigens, the Tn antigen is particularly highly expressed in many carcinomas, especially in breast carcinoma. We designed MAG-Tn3, a fully synthetic vaccine based on three consecutive Tn moieties that are O-linked to a CD4+ T cell epitope, to induce anti-Tn antibody responses that could be helpful for therapeutic vaccination against cancer. To ensure broad coverage within the human population, the tetanus toxoid-derived peptide TT830-844 was selected as a T-helper epitope because it can bind to various HLA-DRB molecules. We showed that the MAG-Tn3 vaccine, which was formulated with the GSK proprietary immunostimulant AS15 and designed for human cancer therapy, is able to induce an anti-Tn antibody response in mice of various H-2 haplotypes, and this response correlates with the ability to induce a specific T cell response against the TT830-844 peptide. The universality of the TT830-844 peptide was extended to new H-2 and HLA-DRB molecules that were capable of binding this T cell epitope. Finally, the MAG-Tn3 vaccine was able to induce anti-Tn antibody responses in cynomolgus monkeys, which targeted Tn-expressing tumor cells and mediated tumor cell death both in vitro and in vivo. Thus, MAG-Tn3 is a highly promising anticancer vaccine that is currently under evaluation in a phase I clinical trial.Electronic supplementary materialThe online version of this article (doi:10.1007/s00262-016-1802-0) contains supplementary material, which is available to authorized users.