Since the discovery and definition of neutrophil extracellular traps (NETs) 14 years ago, numerous characteristics and physiological functions of NETs have been uncovered. Nowadays, the field continues to expand and novel mechanisms that orchestrate formation of NETs, their previously unknown properties, and novel implications in disease continue to emerge. The abundance of available data has also led to some confusion in the NET research community due to contradictory results and divergent scientific concepts, such as pro-and anti-inflammatory roles in pathologic conditions, demarcation from other forms of cell death, or the origin of the DNA that forms the NET scaffold. Here, we present prevailing concepts and state of the science in NET-related research and elaborate on open questions and areas of dispute.

The presence of donor-specific HLA antibodies before or after transplantation may have different implications based on the antibody strength. Yet, current approaches do not provide information regarding the true antibody strength as defined by antigen-antibody dissociation rate. To assess currently available methods, we compared between neat mean fluorescence intensity (MFI) values, C1q MFI values, ethylenediaminetetraacetic acid (EDTA)-treated samples, as well as titration studies and peak MFI values of over 7000 Luminex-based single-antigen HLA antibody data points. Our results indicate that neat MFI values do not always accurately depict antibody strength. We further showed that EDTA treatment (6%) does not always remove all inhibitory factors compared with C1q or titration studies. In this study of patients presenting with multiple antibody specificities, a prozone effect was observed in 71% of the cohort (usually not affecting all antibody specificities within a single serum sample, though). Similar to titration studies, the C1q assay was able to address the issue of potential inhibition; however, its limitation is its low sensitivity and inability to detect the presence of weak antibodies. Titration studies are the only method among the approaches used in this study to provide information suggesting antigen-antibody dissociation rates and are, therefore, likely to provide better indication of true antibody strength.Abbreviations: AMR, antibody-mediated rejection; DSA, donor-specific antibody; EDTA, ethylenediaminetetraacetic acid; MFI, mean fluorescence intensity; SAB, single antigen beads; SPA, solid phase assays

SUMMARY An important function of immunoreceptor tyrosine-based activation motif (ITAM)-coupled receptors is cross-regulation of heterologous receptor signaling, but mechanisms of cross-inhibition are poorly understood. We show that high avidity ligation of ITAM-coupled β2 integrins and FcγRs in macrophages inhibited type I interferon receptor and Toll-like receptor (TLR) signaling and induced expression of interleukin-10 (IL-10), signaling inhibitors SOCS3, ABIN-3 and A20, and repressors of cytokine gene transcription STAT3 and Hes1. Induction of inhibitors was dependent on a pathway comprised of signaling molecules DAP12, Syk, and Pyk2 that coupled to downstream kinases p38 and MSKs, and required integration of IL-10-dependent and independent signals. ITAM-induced inhibitors abrogated TLR responses by cooperatively targeting distinct steps in TLR signaling. Inhibitory signaling was suppressed by IFN-γ and attenuated in inflammatory arthritis synovial macrophages. These results provide an indirect mechanism of cross-inhibition of TLRs and delineate a signaling pathway important for deactivation of macrophages.

While T cells are important for the pathogenesis of systemic lupus erythematosus (SLE) and lupus nephritis, little is known about how T cells function after infiltrating the kidney. The current paradigm suggests that kidney-infiltrating T cells (KITs) are activated effector cells contributing to tissue damage and ultimately organ failure. Herein, we demonstrate that the majority of CD4+ and CD8+ KITs in 3 murine lupus models are not effector cells, as hypothesized, but rather express multiple inhibitory receptors and are highly dysfunctional, with reduced cytokine production and proliferative capacity. In other systems, this hypofunctional profile is linked directly to metabolic and specifically mitochondrial dysfunction, which we also observed in KITs. The T cell phenotype was driven by the expression of an "exhausted" transcriptional signature. Our data thus reveal that the tissue parenchyma has the capability of suppressing T cell responses and limiting damage to self. These findings suggest avenues for the treatment of autoimmunity based on selectively exploiting the exhausted phenotype of tissue-infiltrating T cells.

of lupus. Either over-or underexpression in B cells led to suppression or exacerbation of lupus phenotypes, respectively. Deletion of Tlr9 via any of the other tested Cre lines failed to show a phenotype, together suggesting that B cell TLR9 expression was both necessary and sufficient to modulate SLE pathogenesis.