PD-1 is an immunoinhibitory receptor expressed by activated T cells, B cells, and myeloid cells. Mice deficient in PD-1 exhibit a breakdown of peripheral tolerance and demonstrate multiple autoimmune features. We report here that the ligand of PD-1 (PD-L1) is a member of the B7 gene family. Engagement of PD-1 by PD-L1 leads to the inhibition of T cell receptor–mediated lymphocyte proliferation and cytokine secretion. In addition, PD-1 signaling can inhibit at least suboptimal levels of CD28-mediated costimulation. PD-L1 is expressed by antigen-presenting cells, including human peripheral blood monocytes stimulated with interferon γ, and activated human and murine dendritic cells. In addition, PD-L1 is expressed in nonlymphoid tissues such as heart and lung. The relative levels of inhibitory PD-L1 and costimulatory B7-1/B7-2 signals on antigen-presenting cells may determine the extent of T cell activation and consequently the threshold between tolerance and autoimmunity. PD-L1 expression on nonlymphoid tissues and its potential interaction with PD-1 may subsequently determine the extent of immune responses at sites of inflammation.

Human B lymphoblastoid cell lines facilitate the growth in vitro of human NK cells and of T cell clones (1-4), and together with a source of IL-2, have been successfully used to maintain both NK and T cell clones in culture (1, 2). We have shown that irradiated B lymphoblastoid cell lines induce proliferation of purified human NK cells only in synergy with IL-2 (3). They also facilitate continued proliferation and enhance the cloning efficiency of purified human NK cells in limiting dilution assays in the presence of IL-2 without increasing the proportion (>507o) of NK cells entering the cell cycle in response to IL-2 (4). During culture of total PBMC with irradiated B cell lines, NK cells become activated, as shown by increased cytotoxic activity, by proliferation, and by expression of surface activation antigens such as class II HLA antigens, transferrin receptors, and IL-2 receptors (5, 6). In these cultures, a preferential proliferation of CD16+ CD56(NKH-1)+ CD3 -NK cells is observed (6) : in 10-d cultures, NK cell number is increased 25-fold, whereas T cell number is increased only 3-fold . Elimination of CD4 + cells or the presence of an anti-IL-2 antiserum completely prevents NK cell proliferation (6), suggesting that this probably depends on the production of IL-2 by CD4 + T cells upon allogeneic stimulation . However, the B cell lines also contribute directly to the proliferation of NK cells because in the absence of B cell lines neither high doses of IL-2 alone nor stimulation by allogeneic PBMC induce preferential proliferation of NK cells (6) .The mechanism by which B lymphoblastoid cell lines affect lymphocyte proliferation is not known . Studies with both human and murine lymphocytes (7, 8) suggest a role for immune interferon (IFN -'Y) in NK and T cell proliferation, although other studies (4) have shown that IFN-y production is not required. IFN-'Y is produced in cultures of thymocytes with irradiated B lymphoblastoid cell lines (9) . Low density murine spleen B cells (10) and certain human B cell lines (Cassatella, M . A .,

Engagement of the immunoinhibitory receptor, programmed death-1 (PD-1) attenuates T-cell receptor (TCR)-mediated activation of IL-2 production and T-cell proliferation. Here, we demonstrate that PD-1 modulation of T-cell function involves inhibition of TCR-mediated phosphorylation of ZAP70 and association with CD3f. In addition, PD-1 signaling attenuates PKCh activation loop phosphorylation in a cognate TCR signal. PKCh has been shown to be required for T-cell IL-2 production. A phosphorylated PD-1 peptide, corresponding to the C-terminal immunoreceptor tyrosine-switch motif (ITSM), acts as a docking site in vitro for both SHP-2 and SHP-1, while the phosphorylated peptide containing the N-terminal PD-1 immunoreceptor tyrosine based inhibitory motif (ITIM) associates only with SHP-2.

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IL-17A and IL-17F, produced by the Th17 CD4+ T cell lineage, have been linked to a variety of inflammatory and autoimmune conditions. We recently reported that activated human CD4+ T cells produce not only IL-17A and IL-17F homodimers but also an IL-17F/IL-17A heterodimeric cytokine. All three cytokines can induce chemokine secretion from bronchial epithelial cells, albeit with different potencies. In this study, we used small interfering RNA and Abs to IL-17RA and IL-17RC to demonstrate that heterodimeric IL-17F/IL-17A cytokine activity is dependent on the IL-17RA/IL-17RC receptor complex. Interestingly, surface plasmon resonance studies indicate that the three cytokines bind to IL-17RC with comparable affinities, whereas they bind to IL-17RA with different affinities. Thus, we evaluated the effect of the soluble receptors on cytokine activity and we find that soluble receptors exhibit preferential cytokine blockade. IL-17A activity is inhibited by IL-17RA, IL-17F is inhibited by IL-17RC, and a combination of soluble IL-17RA/IL-17RC receptors is required for inhibition of the IL-17F/IL-17A activity. Altogether, these results indicate that human IL-17F/IL-17A cytokine can bind and signal through the same receptor complex as human IL-17F and IL-17A. However, the distinct affinities of the receptor components for IL-17A, IL-17F, and IL-17F/IL-17A heterodimer can be exploited to differentially affect the activity of these cytokines.

To date, the development of disease-modifying therapies for Alzheimer’s disease (AD) has largely focused on the removal of amyloid beta Aβ fragments from the CNS. Proteomic profiling of patient fluids may help identify novel therapeutic targets and biomarkers associated with AD pathology. Here, we applied the Olink™ ProSeek immunoassay to measure 270 CSF and plasma proteins across 415 Aβ- negative cognitively normal individuals (Aβ- CN), 142 Aβ-positive CN (Aβ+ CN), 50 Aβ- mild cognitive impairment (MCI) patients, 75 Aβ+ MCI patients, and 161 Aβ+ AD patients from the Swedish BioFINDER study. A validation cohort included 59 Aβ- CN, 23 Aβ- + CN, 44 Aβ- MCI and 53 Aβ+ MCI. To compare protein concentrations in patients versus controls, we applied multiple linear regressions adjusting for age, gender, medications, smoking and mean subject-level protein concentration, and corrected findings for false discovery rate (FDR, q < 0.05). We identified, and replicated, altered levels of ten CSF proteins in Aβ+ individuals, including CHIT1, SMOC2, MMP-10, LDLR, CD200, EIF4EBP1, ALCAM, RGMB, tPA and STAMBP (− 0.14 < d < 1.16; q < 0.05). We also identified and replicated alterations of six plasma proteins in Aβ+ individuals OSM, MMP-9, HAGH, CD200, AXIN1, and uPA (− 0.77 < d < 1.28; q < 0.05). Multiple analytes associated with cognitive performance and cortical thickness (q < 0.05). Plasma biomarkers could distinguish AD dementia (AUC = 0.94, 95% CI = 0.87–0.98) and prodromal AD (AUC = 0.78, 95% CI = 0.68–0.87) from CN. These findings reemphasize the contributions of immune markers, phospholipids, angiogenic proteins and other biomarkers downstream of, and potentially orthogonal to, Aβ- and tau in AD, and identify candidate biomarkers for earlier detection of neurodegeneration.Electronic supplementary materialThe online version of this article (10.1186/s40478-019-0795-2) contains supplementary material, which is available to authorized users.

Lubricin is a secreted, cytoprotective glycoprotein that contributes to the essential boundary lubrication mechanisms necessary for maintaining low friction levels at articular cartilage surfaces. Diminishment of lubricin function is thereby implicated as an adverse contributing factor in degenerative joint diseases such as osteoarthritis. Lubricin occurs as a soluble component of synovial fluid, and is synthesized and localized in the superficial layer of articular cartilage (and thus has also been described as ''superficial zone protein'', or SZP); however, defined interactions responsible for lubricin retention at this site are not well characterized. In the current studies, we identified molecular determinants that enable lubricin to effectively bind to articular cartilage surfaces. Efficient and specific binding to the superficial zone was observed for synovial lubricin, as well as for recombinant full-length lubricin and a protein construct comprising the lubricin Cterminal (hemopexin-like) domain (LUB-C, encoded by exons 7-12). A construct representing the Nterminal region of lubricin (LUB-N, encoded by exons 2-5) exhibited no appreciable cartilagebinding ability, but displayed the capacity to dimerize, and thus potentially influence lubricin aggregation. Disulfide bond disruption significantly attenuated recombinant lubricin and LUB-C binding to cartilage surfaces, demonstrating a requirement for protein secondary structure in facilitating the appropriate localization of lubricin at relevant tissue interfaces. These findings help identify additional key attributes contributing to lubricin functionality, which would be expected to be instrumental in maintaining joint homeostasis. ß

A member of the novel protein kinase C (PKC) subfamily, PKC, is an essential component of the T cell synapse and is required for optimal T cell activation and interleukin-2 production. Selective involvement of PKC in TCR signaling makes this enzyme an attractive therapeutic target in T cell-mediated disease processes. In this report we describe the crystal structure of the catalytic domain of PKC at 2.0-Å resolution. Human recombinant PKC kinase domain was expressed in bacteria as catalytically active phosphorylated enzyme and co-crystallized with its subnanomolar, ATP site inhibitor staurosporine. The structure follows the classic bilobal kinase fold and shows the enzyme in its active conformation and phosphorylated state. Inhibitory interactions between conserved features of staurosporine and the ATP-binding cleft are accompanied by closing of the glycine-rich loop, which also maintains an inhibitory arrangement by blocking the phosphate recognition subsite. The two major phosphorylation sites, Thr-538 in the activation loop and Ser-695 in the hydrophobic motif, are both occupied in the structure, playing key roles in stabilizing active conformation of the enzyme and indicative of PKC autocatalytic phosphorylation and activation during bacterial expression. The PKC-staurosporine complex represents the first kinase domain crystal structure of any PKC isotypes to be determined and as such should provide valuable insight into PKC specificity and into rational drug design strategies for PKC selective leads. Inhibitors of PKC1 are currently being used in clinical trials for various types of cancer, and a PKC␤ inhibitor is being used in clinical trials for diabetes-related retinopathy (1).PKC and PKB/AKT kinase domains are related by sequence homology; however, there are key structural differences in the regulatory domains and second messenger cofactor requirements. PKB/AKT contains an N-terminal pleckstrin homology domain regulated by phosphoinositide second messengers, a central catalytic kinase domain, and a C-terminal regulatory region facilitating key protein-protein interactions with signal-