Legumes (Fabaceae or Leguminosae) are unique among cultivated plants for their ability to carry out endosymbiotic nitrogen fixation with rhizobial bacteria, a process that takes place in a specialized structure known as the nodule. Legumes belong to one of the two main groups of eurosids, the Fabidae, which includes most species capable of endosymbiotic nitrogen fixation 1. Legumes comprise several evolutionary lineages derived from a common ancestor 60 million years ago (Mya). Papilionoids are the largest clade, dating nearly to the origin of legumes and containing most cultivated species 2. Medicago truncatula (Mt) is a long-established model for the study of legume biology. Here we describe the draft sequence of the Mt euchromatin based on a recently completed BAC-assembly supplemented with Illumina-shotgun sequence, together capturing ~94% of all Mt genes. A whole-genome duplication (WGD) approximately 58 Mya played a major role in shaping the Mt genome and thereby contributed to the evolution of endosymbiotic nitrogen fixation. Subsequent to the WGD, the Mt genome experienced higher levels of rearrangement than two other sequenced legumes, Glycine max (Gm) and Lotus japonicus (Lj). Mt is a close relative of alfalfa (M. sativa), a widely cultivated crop with limited genomics tools and complex autotetraploid genetics. As such, the Mt genome sequence provides significant opportunities to expand alfalfa’s genomic toolbox.

Legumes and many nonleguminous plants enter symbiotic interactions with microbes, and it is poorly understood how host plants respond to promote beneficial, symbiotic microbial interactions while suppressing those that are deleterious or pathogenic. Trans-acting siRNAs (tasiRNAs) negatively regulate target transcripts and are characterized by siRNAs spaced in 21-nucleotide (nt) ''phased'' intervals, a pattern formed by DICER-LIKE 4 (DCL4) processing. A search for phased siRNAs (phasiRNAs) found at least 114 Medicago loci, the majority of which were defense-related NB-LRR-encoding genes. We identified three highly abundant 22-nt microRNA (miRNA) families that target conserved domains in these NB-LRRs and trigger the production of trans-acting siRNAs. High levels of small RNAs were matched to >60% of all~540 encoded Medicago NB-LRRs; in the potato, a model for mycorrhizal interactions, phasiRNAs were also produced from NB-LRRs. DCL2 and SGS3 transcripts were also cleaved by these 22-nt miRNAs, generating phasiRNAs, suggesting synchronization between silencing and pathogen defense pathways. In addition, a new example of apparent ''two-hit'' phasiRNA processing was identified. Our data reveal complex tasiRNA-based regulation of NB-LRRs that potentially evolved to facilitate symbiotic interactions and demonstrate miRNAs as master regulators of a large gene family via the targeting of highly conserved, protein-coding motifs, a new paradigm for miRNA function.

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Trogocytosis is the uptake of membrane fragments from one cell by another and has been described for immune cells in mice and humans. Functional consequences of trogocytosis are emerging, but a dramatic immune function has still to be associated with it. Here we show that some resting, and most activated, CD4 ؉ and CD8 ؉ T cells acquire immunosuppressive HLA-G1 from antigen-presenting cells (APCs) in a few minutes. Acquisition of HLA-G through membrane transfers does not change the real nature of the T cells but immediately reverses their function from effectors to regulatory cells. These regulatory cells can inhibit allo-proliferative responses through HLA-G1 that they acquired. These data demonstrate that trogocytosis of HLA-G1 leads to instant generation of a new type of regulatory cells, which act through cell-surface molecules they temporarily display but do not express themselves. Such regulatory cells whose existence is most likely limited in space and time might constitute an "emergency" immune suppression mechanism used by HLA-G-expressing tissues to protect themselves against immune aggression. In addition, T cells acquire from HLA-Gexpressing APCs their HLA-G-dependent capability to induce the slower differentiation of regulatory cells that act independently of HLA-G. These data re-emphasize the significance of HLA-G expression in normal and pathologic situations. Introduction"Trogocytosis" is a new name for "fast, cell-to-cell contactdependent uptake of membranes and associated molecules." 1 Trogocytosis has been documented in T and B lymphocytes, natural killer (NK) cells, antigen-presenting cells (APCs), and tumor cells (reviewed in Hudrisier and Bongrand 2 ). Most of the work on trogocytosis by T cells was done in the murine system, in which it was shown that CD4 ϩ and CD8 ϩ T cells acquired APC major histocompatibility complex (MHC) class II and MHC class I molecules, respectively, in an antigen-specific manner [3][4][5][6][7] : for trogocytosis to occur, T-cell receptor (TCR) engagement was necessary, and activation or anti-CD3 increased trogocytosis efficiency. 8,9 Yet, there is no strict dependence of trogocytosis on TCR engagement: (1) in some systems, trogocytosis was shown to depend on CD28 engagement 5 ; and (2) transfer of MHC class II antigens from APCs to T cells can occur in an all-autologous system. 8 Even though most of the work on APC material acquisition by T cells was done on MHC molecules, it was shown that costimulatory molecules B7-1 (CD80), B7-2 (CD86), and ICAM-1 (CD54) are also acquired by murine antigen-specific T cells. 5,10 Trogocytosis is a transfer of membrane fragments, not of individual molecules. Consequently, all molecules contained within a certain membrane area are transferred from one cell to another during trogocytosis, including some that might have nothing to do with the acquirer cell, or participate in cell-to-cell cross-talk. Thus, during trogocytosis, some molecules transfer passively. This was clearly evidenced by showing that CD8 ϩ T cells can acquire MH...

Changes in serum IL-8 levels could be used to monitor and predict clinical benefit from immune checkpoint blockade in melanoma and NSCLC patients.

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BACKGROUND: Around 50% of cutaneous melanomas harbor the BRAF V600E mutation and can be treated with BRAF inhibitors. DNA carrying this mutation can be released into circulation as cell-free BRAF

Purpose: Interleukin-8 (IL8) is a chemokine produced by malignant cells of multiple cancer types. It exerts various functions in shaping protumoral vascularization and inflammation/immunity. We evaluated sequential levels of serum IL8 in preclinical tumor models and in patients to assess its ability to estimate tumor burden.Experimental Design: IL8 levels were monitored by sandwich ELISAs in cultured tumor cells supernatants, tumor-xenografted mice serum, and in samples from 126 patients with cancer. We correlated IL8 serum levels with baseline tumor burden and with treatment-induced changes in tumor burden, as well as with prognosis.Results: IL8 concentrations correlated with the number of IL8-producing tumor cells in culture. In xenografted neoplasms, IL8 serum levels rapidly dropped after surgical excision, indicating an accurate correlation with tumor burden. In patients with melanoma (n ¼ 16), renal cell carcinoma (RCC; n ¼ 23), non-small cell lung cancer (NSCLC; n ¼ 21), or hepatocellular carcinoma (HCC; n ¼ 30), serum IL8 concentrations correlated with tumor burden and stage, survival (melanoma, n ¼ 16; RCC, n ¼ 23; HCC, n ¼ 33), and objective responses to therapy, including those to BRAF inhibitors (melanoma, n ¼ 16) and immunomodulatory monoclonal antibodies (melanoma, n ¼ 8). IL8 concentrations in urine (n ¼ 18) were mainly elevated in tumors with direct contact with the urinary tract.Conclusions: IL8 levels correlate with tumor burden in preclinical models and in patients with cancer.