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BackgroundSeasonal variations have been reported for immune markers. However, the relative contributions of sunlight and vitamin D variability on such seasonal changes are unknown.ObjectiveThis double-blind, randomized, placebo-controlled trial tested whether daily 400 IU vitamin D3supplementation affected short-term (12 weeks) and long-term (43 weeks) natural regulatory T cell (nTreg) populations in healthy participants.Design62 subjects were randomized equally to vitamin D versus placebo in March and assessed at baseline, April (4w), June (12w), September (25w) and January (43w). Circulating nTregs,ex vivoproliferation, IL-10 and IFN-γ productions were measured. Vitamin D metabolites and sunlight exposure were also assessed.ResultsMean serum 25-hydroxyvitamin D (25(OH)D) increased from 35.8(SD 3.0) to 65.3(2.6) nmol/L in April and remained above 75 nmol/L with vitamin D supplementation, whereas it increased from 36.4(3.2) to 49.8(3.5) nmol/L in June to fall back to 39.6(3.5) nmol/L in January with placebo. Immune markers varied similarly between groups according to the season, but independently of 25(OH)D. For nTregs, the mean (%CD3+CD4+CD127locells (SEM)) nadir observed in March (2.9(0.1)%) peaked in September at 4.0(0.2)%. Mean T cell proliferation peaked in June (33156(1813) CPM) returning to the nadir in January (17965(978) CPM), while IL-10 peaked in June and reached its nadir in September (median (IQR) of 262(283) to (121(194) pg/ml, respectively). Vitamin D attenuated the seasonal increase in IFN-γ by ~28% with mean ng/ml (SEM) for placebo vs vitamin D, respectively, for April 12.5(1.4) vs 10.0(1.2) (p=0.02); June 13.9(1.3) vs 10.2(1.7) (p=0.02) and January 7.4(1.1) vs 6.0(1.1) (p=0.04).ConclusionsDaily low dose Vitamin D intake did not affect the nTregs population. There were seasonal variation in nTregs, proliferative response and cytokines, suggesting that environmental changes influence immune response, but the mechanism seems independent of vitamin D status. Vitamin D attenuated the seasonal change in T cell-produced IFN-γ, suggesting a decrease in effector response which could be associated with inflammation.Clinical Trial Registrationhttps://www.isrctn.com, identifier (ISRCTN 73114576).

Platelet destruction in immune thrombocytopenia is caused by autoreactive antibody and T-cell responses, most commonly directed against platelet glycoprotein IIb/IIIa. Loss of self-tolerance in the disease is also associated with deficient activity of regulatory T cells. Having previously mapped seven major epitopes on platelet glycoprotein IIIa that are recognized by helper T cells from patients with immune thrombocytopenia, the aim was to test whether peptide therapy with any of these sequences, alone or in combination, could inhibit responses to the antigen in humanized mice expressing HLA-DR15. None of the individual peptides, delivered by a putative tolerogenic regimen, consistently suppressed the antibody response to subsequent immunization with human platelet glycoprotein IIb/IIIa. However, the combination of glycoprotein IIIa peptides aa6-20 and aa711-725, which contain the predominant helper epitopes in patients and elicited the strongest trends to suppress when used individually, did abrogate this response. The peptide combination also blunted, but did not reverse, the ongoing antibody response when given after immunization. Suppression of antibody was associated with reduced splenocyte T-cell responsiveness to the antigen, and with the induction of a regulatory T-cell population that is more responsive to the peptides than to purified platelet glycoprotein IIb/IIIa. Overall, these data demonstrate that combinations of peptides containing helper epitopes, such as platelet glycoprotein IIIa aa6-20 and aa711-725, can promote in vivo suppression of responses to the major antigen implicated in immune thrombocytopenia. The approach offers a promising therapeutic option to boost T-cell regulation, which should be taken forward to clinical trials.

Macrophages are key in orchestrating immune responses to micro-environmental stimuli, sensed by a complex set of surface receptors. The human cell line THP-1 has a monocytic phenotype, including the ability to differentiate into macrophages, providing a tractable, standardised surrogate for human monocyte-derived macrophages. Here we assessed the expression of 49 surface markers including Fc, complement, C-type lectin and scavenger receptors; TIMs; Siglecs; and co-stimulatory molecules by flow cytometry on both THP-1 monocytes and macrophages and following macrophage activation with seven standard conditioning/polarizing stimuli. Of the 34 surface markers detected on macrophages, 18 altered expression levels on activation. From these, expression of 9 surface markers were consistently altered by all conditioning regimens, while 9 were specific to individual polarizing stimuli. This study provides a resource for the study of macrophages and highlights that macrophage polarization states share much in common and the differences do not easily fit a simple classification system.

Non‐immune cells are increasingly recognized as important in regulating immunity, but the role of red blood cells (RBC) remains relatively unexplored, despite their abundance in the circulation and a cell surface rich in potential ligands. Here, we determine whether RBC influence the activation state of human B cells. Separation of RBC from peripheral blood mononuclear cells increased B‐cell expression of HLA‐DR/DP/DQ, whilst reconstitution reduced the levels of B‐cell activation markers HLA‐DR/DP/DQ, CD86, CD69 and CD40, as well as decreasing proliferative responses and IgM secretion. Inhibition of B cells required contact with RBC and was abrogated by either removal of sialic acids from RBC or blocking the corresponding lectin receptor CD22 on B cells. Chronic lymphocytic leukaemia B cells express low levels of CD22 and were less susceptible to inhibition by RBC, which may contribute to their activated phenotype. Taken together, the results identify a novel mechanism that may suppress inappropriate responsiveness of healthy B cells whilst circulating in the bloodstream., Contact with red blood cells (RBC) suppresses the activation of human B‐cells. Separation of RBC from peripheral blood mononuclear cells increases B‐cell expression of HLA‐DR/DP/DQ, whilst reconstitution reduces the levels of B‐cell activation markers HLA‐DR/DP/DQ, CD86, CD69 and CD40, as well as decreasing proliferative responses and IgM secretion. Inhibition is mediated via ligation of the B‐cell lectin receptor CD22 by sialic acid on RBC, and represents a novel mechanism that may suppress inappropriate responsiveness of B‐cells while they are circulating in the bloodstream.

In both sickle cell disease and malaria, red blood cells (RBCs) are phagocytosed in the spleen, but receptor-ligand pairs mediating uptake have not been identified. Here, we report that patches of high mannose N-glycans (Man5-9GlcNAc2), expressed on diseased or oxidized RBC surfaces, bind the mannose receptor (CD206) on phagocytes to mediate clearance. We find that extravascular hemolysis in sickle cell disease correlates with high mannose glycan levels on RBCs. Furthermore, Plasmodium falciparum-infected RBCs expose surface mannose N-glycans, which occur at significantly higher levels on infected RBCs from sickle cell trait subjects compared to those lacking hemoglobin S. The glycans are associated with high molecular weight complexes and protease-resistant, lower molecular weight fragments containing spectrin. Recognition of surface N-linked high mannose glycans as a response to cellular stress is a molecular mechanism common to both the pathogenesis of sickle cell disease and resistance to severe malaria in sickle cell trait., Red blood cells (RBCs) are phagocytosed in the spleen in sickle cell disease and malaria. Here, Cao et al. show that high mannose N-glycans, exposed on diseased or oxidized RBC surfaces, bind mannose receptor CD206 on host cells, mediating phagocytosis.

In both sickle cell disease (SCD) and malaria, red blood cells (RBCs) are phagocytosed in the spleen, but receptor-ligand pairs mediating uptake have not been identified. Here, we report that patches of high mannose N-glycans (Man5-9GlcNAc2), expressed on diseased or oxidized RBC surfaces, bind the mannose receptor (CD206) on phagocytes to mediate clearance. Extravascular haemolysis in SCD correlates with high mannose glycan levels on RBCs. Infection of RBCs withPlasmodium falciparumexpose surface mannose N-glycans on healthy RBCs, which occurred at significantly higher levels on RBCs from subjects with sickle cell trait compared to those lacking haemoglobin S. The glycans were associated with high molecular weight complexes and protease-resistant, lower molecular weight fragments containing spectrin. Recognition of surface N-linked high mannose glycans, a novel response to cellular stress, is the first molecular mechanism common to both the pathogenesis of SCD and resistance to severe malaria in sickle cell trait.

To the Editor: Systemic lupus erythematosus (SLE) is a multisystem autoimmune disorder characterized by fluctuating levels of immune response hyperactivity, high serum titers of nucleic antigen-specific autoantibodies, and persistent production of type-I interferon (IFN)1. One route to controlling SLE has been to exploit the properties of T cell lymphocyte costimulation inhibitor (CTLA-4), a selective costimulation inhibitor, which suppresses auto-antigen-specific T cell response intensity2. Although the full-length cell-surface receptor CTLA-4 is well characterized, other alternatively spliced isoforms exist, including a soluble form of the molecule (sCTLA-4)3. Initial analysis of sCTLA-4 in patients with SLE described raised serum levels compared with healthy donors, and sCTLA-4 levels correlated with disease activity4, but little is known of whether it plays any role in SLE. Currently, this is a relevant question because there is anecdotal evidence that CTLA4-Ig can have clinical benefits for some patients with SLE5. Studies of sCTLA-4 using current anti–CTLA-4 antibodies should be interpreted with caution because they are raised against the extracellular region, found in the receptor, cleaved receptor artifact and the soluble isoform, hence obscuring the contribution of native sCTLA-4. Here, using antibodies raised specifically against native sCTLA-46,7, we determined whether sCTLA-4 contributes to the immune response underlying SLE, particularly regarding SLE markers IFN-α and anti-dsDNA antibody levels. The study included 104 patients with SLE and 40 healthy volunteer donors and first compared serum levels of IFN-α (Figure 1). All methods were carried out in accordance with the Grampian … Address correspondence to F.J. Ward, University of Aberdeen, Immunity, Infection and Inflammation group, Division of Applied Medicine, Institute of Medical Sciences, Foresterhill, Aberdeen, UK. E-mail: mmd475{at}abdn.ac.uk or L.N. Dahal, L.N.Dahal{at}liverpool.ac.uk

The factors and signals driving T cell activation and polarisation during immune responses have been studied mainly at the level of cells and chemical mediators. Here we describe a physical driver of these processes in the form of physiological-strength electric fields (EFs). EFs are generated at sites where epithelium is disrupted (e.g. wounded skin/bronchial epithelia) and where T cells frequently are present. Using live-cell imaging, we show human primary T cells migrate directionally to the cathode in low strength (50/150 mV/mm) EFs. Strikingly, we show for the first time that EFs significantly downregulate T cell activation following stimulation with antigen-activated APCs or anti-CD3/CD28 antibodies, as demonstrated by decreased IL-2 secretion and proliferation. These EF-induced functional changes were accompanied by a significant dampening of CD4+ T cell polarisation. Expression of critical markers of the Th17 lineage, RORγt and IL-17, and the Th17 polarisation mediator phospho-STAT3 were reduced significantly, while STAT1, ERK and c-Jun phosphorylation were comparatively unaffected suggesting STAT3 modulation by EFs as one mechanism driving effects. Overall, we identify electrical signals as important contributors to the co-ordination and regulation of human T cell functions, paving the way for a new research area into effects of naturally occurring and clinically-applied EFs in conditions where control of T cell activity is paramount.

Background Psoriasis is a chronic T-cell-mediated skin disease with marked social and economic burdens. Current treatments are unsatisfactory, with unpredictable remission times and incompletely understood modes of action. Recent advances in our understanding of the pathogenesis of psoriasis have identified the imbalance between CD4+ T effector cells, particularly the T helper (Th)17 subset, and regulatory T cells (Tregs) as key to the development of psoriatic lesions, and therefore a novel therapeutic target. Objectives To quantify in patients the effects of three commonly used psoriasis treatment modalities on the Th1, Th2, Th17 and Treg subsets, and to test whether any change correlates with clinical response. Methods Flow cytometry was used to enumerate Th1, Th2, Th17 and Treg subsets in blood and skin of patients with psoriasis before and after receiving any of the following treatments: narrowband ultraviolet B (NB-UVB), adalimumab and topical betamethasone-calcipotriol combination (Dovobet® ) RESULTS: All patients responded clinically to the treatments. NB-UVB significantly increased the numbers of circulating and skin Tregs, while, by contrast, adalimumab reduced Th17 cells in these compartments, and Dovobet had dual effects by both increasing Tregs and reducing Th17 cells. Conclusions The differential effects reported here for the above-mentioned treatment modalities could be exploited to optimize or design therapeutic strategies to overcome the inflammatory drivers more effectively and restore the Th17-Treg balance in psoriasis.

Heterozygosity for Hemoglobin (Hb) S, sickle cell trait (SCT), affects over 40 million people and confers resistance to severe infection by Plasmodium falciparum. Homozygosity for HbS, or compound heterozygosity with certain other alleles of Hb, affects over 4 million individuals and causes sickle cell disease (SCD). Hemolytic anaemia is a prominent feature of SCD and is mainly extravascular, mediated by hepatic and splenic macrophages. No ligands for this process have been identified. As many macrophage phagocytic receptors recognise carbohydrates, we surveyed surface glycan expression by sickle cells using a panel of 8 lectins and flow cytometry. Most glycans were similar to those of healthy red blood cells (RBC), except much higher expression of terminal mannose. We investigated the structural basis for these residues using glycomic mass spectroscopy, which showed them to be N-linked high (Man5-9GlcNAc2) mannoses, a surprising conclusion as these are usually intermediates in the formation of complex glycans and not displayed on cell surfaces. High resolution microscopy revealed the mannose residues to be carried in discrete microdomains on the surfaces of sickle cells. These structures were absent on the surfaces of healthy RBC, instead being present in the membrane skeleton under the cell surface. Lectin blots and immunoprecipitation showed the mannoses to co-migrate predominantly with spectrin. We showed these mannose-bearing structures were able to stimulate phagocytosis of RBC by using a peripheral blood derived macrophage uptake assay. Sickle RBC were taken up at high rates compared to healthy RBC and this could be inhibited by congeners of mannose. We identified the importance of a cognate ligand (CD206: the mannose receptor) using blocking antibodies and knockdown of CD206 expression using siRNA. The in vivo and pathogenic relevance of mannose exposure was investigated by taking advantage of the heterogeneity of hemolysis in SCD. RBC with SCD (n=94), SCT (n=57) and healthy individuals (n=54) were assayed for mannose exposure by flow cytometry. SCT and healthy RBC showed no mannose exposure but high levels were found on HbSS RBC (p Identification of a ligand pair mediating rapid clearance of sickle cells raised the possibility that they also mediate enhanced clearance of SCT RBC infected by malarial parasites. Indeed, P. falciparum cultures induced mannose expression at the pigmented trophozoite and schizont stages in infected HbAA RBCs, at levels corresponding to mild hemolysis in SCD. Mannose expression in infected HbAS RBCs was even higher, with levels corresponding to severe hemolysis in SCD. Infection with P. falciparum and selection for HbS arose only recently in human evolution, raising the question of what the physiological triggers for this mechanism are. Infection with malarial parasites causes oxidative stress. We therefore subjected healthy RBC to copper sulphate, which resulted in surface mannose exposure as well as uptake by macrophages. Oxidized SCT RBC displayed more mannose than oxidized healthy RBC. Thus, we have identified a new cell surface 'eat me' signalling mechanism that allows inspecting macrophages to engage with the rigid membrane skeleton and phagocytose the mannose displaying cell. The mechanism is stimulated by HbS: when present in high concentrations, the mechanism is activated constitutively, resulting in sickle cell anaemia. Heterozygosity for HbS is insufficient by itself to trigger mannose exposure. However, the mechanism is primed so that oxidative stress associated with infection by P. falciparum causes greater mannose display, increased parasitized cell clearance and protection against severe malaria. These findings should allow the design of inhibitors of sickle cell haemolysis and inducers of protection against malaria. Disclosures Cao: University of Aberdeen: Patents & Royalties. Barker:University of Aberdeen: Patents & Royalties. Vickers:University of Aberdeen: Patents & Royalties; GSK: Equity Ownership.

Background: Reactive oxygen species and other free radicals, together with glucose and its metabolites are believed to play important roles in the aging process. The carbohydrate components of glycosylated proteins are important in mediating cell-cell interactions and a role has been suggested for them in the aging process. Erythrocytes are critical cells in the human body, heavily glycosylated and relatively easily available and so are good candidates to yield insights into how patterns of glycosylation change with age and disease. It has been claimed, based on a periodic acid Schiff assay, that human aging is associated with a decline of erythrocyte surface sialic acids. Plant lectins allow for more specific assays for glycans, including determining the linkage of sialic acids and analysis of single cells by flow cytometry. Methods: Plant lectins, including Maackia amurensis lectin II (MAL), binding to α-2,3 linked sialic acids and Sambucus nigra (SNA), α-2,6 sialic acids, were used in flow cytometry and western blot of erythrocyte surface membrane. N-glycomics mass spectrometry determines glycan structures. Donors varying in age and hyperglycemia, as indicated by HbA1c were analysed. Results: Erythrocyte surface sialic acids have no significant associations with donor age. A combination of storage and cellular aging produces a specific loss of α-2,6 sialic acids. By contrast, erythrocyte surface terminal fucoses increase significantly with donor age. In order to determine which aspects of aging are important in determining this change, we investigated whether this novel human aging biomarker is associated with higher plasma glucose values, assessed by glycated hemoglobin (HbA1c) and reactive oxygen species (ROS) generation. Fucose levels were associated with HbA1c levels, but not ROS generation. Conclusion: Our study identifies novel glycan-based biomarkers for human aging and disease. The simplicity of lectin-based assays provide an attractive cellular tool to study aging and disease processes.

Macrophages are antigen presenting cells that can adopt different activation states as directed by microenvironmental stimuli. It is well-recognised how CD4(+) T helper (Th) signals drive macrophage activation, but the ability of differentially activated human macrophages to stimulate the major types of CD4(+) T helper (Th) response by presenting antigen have not been well defined. Previous studies have focussed on murine cells, undifferentiated human monocytes, or macrophage products, and have been limited to non-physiological mitogenic Th responses. The aim was therefore to compare the Th cell polarising abilities of different human macrophage subsets when presenting specific antigen. We demonstrate for the first time that the way macrophages are activated, while naturally presenting antigen, has profound effects on downstream adaptive immune responses. In autologous co-cultures, LPS-activation was the most potent stimulus for antigen-loaded macrophages to drive Th17 polarisation from both unfractionated CD4(+) T-cells and the CD45RO(+) memory population, while IFNγ/LPS activated macrophages preferentially induced a Th1 phenotype. By contrast, IL-4-activated macrophages were ineffective in inducing responses by either Th subset. Although antigen-loaded dendritic cells were superior to macrophages in driving Th1 responses, the Th17 polarising capacity of the two antigen-presenting cell types was equivalent, and was strongly dependent on IL-1β secretion. Taken together, these results clearly demonstrate for the first time how differentially activated human macrophages present antigen to bias specific, rather than mitogen-driven, Th responses and lead us to propose that they impact adaptive immunity in vivo, particularly in determining Th17 polarisation within inflamed tissues.

Macrophages respond to their microenvironment and develop polarized functions critical for orchestrating appropriate inflammatory responses. Classical (M1) activation eliminates pathogens while alternative (M2) activation promotes regulation and repair. M1 macrophage activation is strongly associated with suppressor of cytokine signalling 3 (SOCS3) expression in vitro, but the functional consequences of this are unclear and the role of SOCS3 in M1-macrophage polarization in vivo remains controversial. To address these questions, we defined the characteristics and function of SOCS3-expressing macrophages in vivo and identified potential mechanisms of SOCS3 action. Macrophages infiltrating inflamed glomeruli in a model of acute nephritis show significant up-regulation of SOCS3 that co-localizes with the M1-activation marker, inducible nitric oxide synthase. Numbers of SOCS3(hi) -expressing, but not SOCS1(hi) -expressing, macrophages correlate strongly with the severity of renal injury, supporting their inflammatory role in vivo. Adoptive transfer of SOCS3-short interfering RNA-silenced macrophages into a peritonitis model demonstrated the importance of SOCS3 in driving production of pro-inflammatory IL-6 and nitric oxide, while curtailing expression of anti-inflammatory IL-10 and SOCS1. SOCS3-induced pro-inflammatory effects were due, at least in part, to its role in controlling activation and nuclear accumulation of nuclear factor-κB and activity of phosphatidylinositol 3-kinase. We show for the first time that SOCS3 also directs the functions of human monocyte-derived macrophages, including efficient M1-induced cytokine production (IL-1β, IL-6, IL-23, IL-12), attenuated signal transducer and activator of transcription 3 activity and ability of antigen-loaded macrophages to drive T-cell responses. Hence, M1-associated SOCS3 was a positive regulator of pro-inflammatory responses in our rodent models and up-regulated SOCS3 is essential for effective M1-macrophage activation and function in human macrophages.

Summary Recent evidence points to the T helper type 17 (Th17) subset as key in the pathogenesis of psoriasis, but cells of this type in lesions remain to be fully characterized. Here we isolated, enumerated, functionally tested and clonotyped the CD4+ Th cell population ex vivo from lesional biopsies and paired peripheral blood samples from psoriasis patients. Th17 cells were over-represented dramatically in lesions from all patients, representing 49–93% of CD4+ Th cells compared with 3–18% in blood. Most lesional Th17 cells produced interleukin (IL)-17A ex vivo without further stimulation and expressed the CD45RO+ phenotype characteristic of activated or memory cells. There was no increase in ‘natural’ [CD25hiforkhead box protein 3 (FoxP3+)] regulatory T cells in lesions versus peripheral blood, but there was enrichment of ‘induced’ IL-10+ regulatory T cell numbers in biopsies from some patients. The lesional Th17 cells exhibited a bias in T cell receptor Vβ chain usage, suggestive of specific expansion by antigen. The therapeutic challenge is to overcome the dominance of overwhelming numbers of such antigen-specific Th17 cells in psoriatic lesions.

Summary Autoimmune haemolytic anaemia (AIHA) is caused by autoantibodies against red blood cell (RBC) surface antigens that render RBC susceptible to Fc-mediated phagocytosis and complement-mediated lysis. Experimental AIHA can be induced by injection of rat RBC to naive mice, but a lymphocyte-mediated regulatory mechanism eventually suppresses the production of autoantibodies specific for mouse RBC. Critically, this tolerogenic response can be transferred to naive mice by splenocytes from the rat RBC-immunized mouse. Here we investigate whether indoleamine 2,3 dioxygenase (IDO) or the initiators of IDO cascade, including the cytotoxic T lymphocyte antigen (CTLA)-4 receptor and its soluble isoform, contribute to this tolerogenic mechanism. Splenocytes from experimental AIHA mice were transferred adoptively to naive mice under the cover of anti-CTLA-4, anti-soluble CTLA-4 antibodies or IDO inhibitor 1-methyl tryptophan (1-MT). Recipient mice were immunized with rat RBC and levels of antibody against self-RBC and rat-RBC were monitored. Our results indicate that transfer of tolerance to naive recipients is dependent upon IDO-mediated immunosuppression, as mice receiving previously tolerized splenocytes under the cover of 1-MT were refractory to tolerance and developed haemolytic disease upon further challenge with rat RBC. Initiators of IDO activity, CTLA-4 or soluble CTLA-4 did not mediate this tolerogenic process but, on their blockade, boosted antigen-specific effector immune responses.

CTLA-4 is a crucial immune regulator that mediates both negative costimulation signals to T cells, and regulatory T (Treg)-cell extrinsic control of effector responses. Here we present evidence supporting a novel mechanism for this extrinsic suppression, executed by the alternatively spliced soluble CTLA-4 isoform (sCTLA-4). Analyses of human T cells in vitro show that sCTLA-4 secretion can be increased during responses, and has potent inhibitory properties, since isoform-specific blockade of its activity significantly increased Ag-driven proliferation and cytokine (IFN-γ, IL-17) secretion. Treg cells were demonstrated to be a prominent source of sCTLA-4, which contributed to suppression in vitro when their numbers were limiting. The soluble isoform was also produced by, and inhibited, murine T cells responding to Ag in vitro, and blockade of its activity in vivo protected against metastatic spread of melanoma in mice. We conclude that sCTLA-4 is an important immune regulator, responsible for at least some of the inhibitory effects previously ascribed to the membrane-bound isoform. These results suggest that the immune system exploits the different CTLA-4 isoforms for either intrinsic or extrinsic regulation of T-cell activity.

Although eosinophils are inflammatory cells, there is increasing attention on their immunomodulatory roles. For example, murine eosinophils can present antigen to CD4+ T helper (Th) cells, but it remains unclear whether human eosinophils also have this ability. This study determined whether human eosinophils present a range of antigens, including allergens, to activate Th cells, and characterized their expression of MHC class II and co-stimulatory molecules required for effective presentation. Human peripheral blood eosinophils purified from non-allergic donors were pulsed with the antigens house dust mite extract (HDM), Timothy Grass extract (TG) or Mycobacterium tuberculosis purified protein derivative (PPD), before co-culture with autologous CD4+ Th cells. Proliferative and cytokine responses were measured, with eosinophil expression of HLA-DR/DP/DQ and the co-stimulatory molecules CD40, CD80 and CD86 determined by flow cytometry. Eosinophils pulsed with HDM, TG or PPD drove Th cell proliferation, with the response strength dependent on antigen concentration. The cytokine responses varied with donor and antigen, and were not biased towards any particular Th subset, often including combinations of pro- and anti-inflammatory cytokines. Eosinophils up-regulated surface expression of HLA-DR/DP/DQ, CD80, CD86 and CD40 in culture, increases that were sustained over 5 days when incubated with antigens, including HDM, or the major allergens it contains, Der p I or Der p II. Human eosinophils can, therefore, act as effective antigen-presenting cells to stimulate varied Th cell responses against a panel of antigens including HDM, TG or PPD, an ability that may help to determine the development of allergic disease.

Background The inhibitory CTLA-4 molecule is a crucial regulator of immune responses and a target for therapeutic intervention in both autoimmunity and cancer. In particular, CTLA-4 is important in controlling antigen-specific immunity, including responses to autoantigens associated with autoimmune disease. Here, we investigate cytokine responses to a range of lupus-associated autoantigens and assess whether the alternatively spliced isoform of CTLA-4, soluble CTLA-4 (sCTLA-4), contributes to immune regulation of autoantigen-specific immunity in systemic lupus erythematosus (SLE). Methods The cell culture supernatant production of sCTLA-4 as well as the cytokines IL-10, IFN-γ, and IL-17 from peripheral blood mononuclear cells (PBMC) from lupus patients and age- and sex-matched healthy volunteer donors were measured in response to previously identified histone and small nuclear ribonucleoprotein (snRNP) autoantigen-derived peptides (H391-105, H471-93, and U170K131-151) by ELISA. We also examined the functional contribution of sCTLA-4 to immune regulation in the context of these autoantigenic peptides following blockade of sCTLA-4 with a selective anti-sCTLA-4 monoclonal antibody, JMW-3B3. Results We identified responses to autoantigenic peptides, which revealed qualitative differences in cytokine (IL-10, IL-17, and IFN-γ) profiles between SLE patients and healthy donors. PBMC from healthy donors responded to each of the lupus peptides by secreting IFN-γ and IL-17, but PBMC from SLE patients produced IL-10. Although we did not observe differences in the levels of serum or PBMC culture supernatant sCTLA-4 in either cohort, blockade of sCTLA-4 in PBMC cultures responding to antigen enhanced the cytokine profiles associated with each group. Conclusion The results show that lupus autoantigen-derived peptides display varied immunogenicity in lupus versus healthy volunteer donors, while sCTLA-4 acts to regulate the T-cell activity independently of response profile. Electronic supplementary material The online version of this article (doi:10.1186/s13075-016-1075-1) contains supplementary material, which is available to authorized users.

Macrophages are heterogeneous cells with diverse phenotypes and sometimes opposing functions. These activities are dictated by activating stimuli in their microenvironment. For example, it is well described how CD4 + T helper (Th) cell-derived cytokines result in different macrophage-activation states. However, much less is known on how differentially-activated macrophages, presenting antigen, can drive the major types of CD4 + Th subpopulations, especially in human systems. Many studies have focussed on dendritic cells as the major antigen-presenting cell shaping T cell responses or on murine macrophage-secreted cytokines in the presence of mitogenic-stimuli, such as CD3/CD28, to induce Th polarization. Recent literature is, however, providing evidence that activated antigen- presenting macrophages can be as efficient as dendritic cells in polarising Th cells, especially Th17, and whilst both these cell types co-exist within inflamed tissue, macrophages are more abundant. The bias towards polarization of particular T cell subsets is strongly dependent on the activation state of macrophages. The concept of targeting macrophages to downregulate inflammatory responses may therefore have further reaching consequences by also abrogating pathogenic Th cells in autoimmune or inflammatory diseases.

The K blood group remains an important target in hemolytic disease of the newborn (HDN), with no immune prophylaxis available. The aim was to characterize the Th response to K as a key step in designing specific immunotherapy and understanding the immunogenicity of the Ag. PBMCs from K-negative women who had anti-K Abs after incompatible pregnancy, and PBMCs from unimmunized controls, were screened for proliferative responses to peptide panels spanning the K or k single amino acid polymorphism. A dominant K peptide with the polymorphism at the C terminus elicited proliferation in 90% of alloimmunized women, and it was confirmed that responding cells expressed helper CD3+CD4+ and “memory” CD45RO+ phenotypes, and were MHC class II restricted. A relatively high prevalence of background peptide responses independent of alloimmunization may contribute to K immunogenicity. First, cross-reactive environmental Ag(s) pre-prime Kell-reactive Th cells, and, second, the K substitution disrupts an N-glycosylation motif, allowing the exposed amino acid chain to stimulate a Th repertoire that is unconstrained by self-tolerance in K-negative individuals. The dominant K peptide was effective in inducing linked suppression in HLA-transgenic mice and can now be taken forward for immunotherapy to prevent HDN because of anti-K responses.

Background Many immune-mediated diseases are associated with low levels of vitamin D and sunlight. UV light or supplementation with vitamin D can increase regulatory T-cell activity and prevent animal models of autoimmune disease. Increasing population vitamin D levels may therefore alleviate the burden of human immune-mediated disease. Objective To determine the responses of circulating 25-hydroxyvitamin D [25(OH)D] levels, regulatory T-cell numbers, and immune function to UV light exposure in patients being treated for skin disease. Methods Twenty-four subjects with skin disease from the North of Scotland were recruited between December and March. At baseline, and after 2 and 4 weeks of narrowband UV light exposure, we measured peripheral blood 25(OH)D level, numbers of regulatory T cells (CD4 + CD25 hi FoxP3 + ), and T-cell proliferative and cytokine responses to anti-CD3/CD28 stimulation. Results Median (interquartile range) narrowband UV-B received during the study was 39.1 (30.9) as standard erythema dose, comparable to a quarter of the median summer sunlight exposure received locally. This increased the 25(OH)D level from a mean ± SD of 34 ± 17 nmol/L to 58 ± 16 nmol/L after 2 weeks and 78 ± 19 nmol/L after 4 weeks. The mean proportion of circulating regulatory T cells increased from 0.5% to 1.6% CD3 + cells, which significantly correlated with the increased 25(OH)D level. UV treatment was also followed by reduced proliferative and IL-10 responses to anti-CD3/CD28 independent of the 25(OH)D level. Conclusion Narrowband UV light reduces systemic immune responsiveness via the induction of regulatory T cells. Light and 25(OH)D levels may affect particular immune functions independently. The levels of serum 25(OH)D over which these effects are apparent should guide future interventions.

Background Interleukin-17A is the signature cytokine of the Th17 subset and drives inflammatory pathology, but its relevance to autoantibody-mediated diseases is unclear. Th1 cells secreting interferon-γ have been implicated in autoimmune hemolytic anemia, so the aim was to determine which cytokine is more closely associated with disease severity. Design and Methods Interferon-γ and interleukin-17A were measured in the sera of patients with autoimmune hemolytic anemia and healthy donors, and in peripheral blood mononuclear cell cultures stimulated with autologous red blood cells, or a panel of peptides spanning red blood cell autoantigen. Results Serum interleukin-17A, but not interferon-γ, was significantly raised in patients with autoimmune hemolytic anemia ( P

Macrophages become activated by their environment and develop polarized functions: classically activated (M1) macrophages eliminate pathogens but can cause tissue injury, whereas alternatively activated (M2) macrophages promote healing and repair. Mechanisms directing polarized activation, especially in vivo, are not understood completely, and here, we examined the role of SOCS proteins. M2 macrophages activated in vitro or elicited by implanting mice i.p. with the parasitic nematode Brugia malayi display a selective and IL-4-dependent up-regulation of SOCS1 but not SOCS3. Using siRNA-targeted knockdown in BMDM, we reveal that the enhanced SOCS1 is crucial for IL-4-induced M2 characteristics, including a high arginase I:iNOS activity ratio, suppression of T cell proliferation, attenuated responses to IFN-γ/LPS, and curtailed SOCS3 expression. Importantly, SOCS1 was essential in sustaining the enhanced PI3K activity that drives M2 activation, defining a new regulatory mechanism by which SOCS1 controls M2 polarization. By contrast, for M1 macrophages, SOCS1 was not only an important regulator of proinflammatory mediators (IL-6, IL-12, MHC class II, NO), but critically, for M1, we show that SOCS1 also restricted IL-10 secretion and arginase I activity, which otherwise would limit the efficiency of M1 macrophage proinflammatory responses. Together, our results uncover SOCS1, not only as a feedback inhibitor of inflammation but also as a critical molecular switch that tunes key signaling pathways to effectively program different sides of the macrophage balance.

The pathogenicity of the opportunistic human fungal pathogenCandida albicansdepends on its ability to escape destruction by the host immune system. Using mutant strains that are defective in cell surface glycosylation, cell wall protein synthesis, and yeast-hypha morphogenesis, we have investigated three important aspects ofC. albicansinnate immune interactions: phagocytosis by primary macrophages and macrophage cell lines, hyphal formation within macrophage phagosomes, and the ability to escape from and kill macrophages. We show that cell wall glycosylation is critically important for the recognition and ingestion ofC. albicansby macrophages. Phagocytosis was significantly reduced for mutants deficient in phosphomannan biosynthesis (mmn4Δ,pmr1Δ, andmnt3 mnt5Δ), whereas O- and N-linked mannan defects (mnt1Δmnt2Δ andmns1Δ) were associated with increased ingestion, compared to the parent wild-type strains and genetically complemented controls. In contrast, macrophage uptake of mutants deficient in cell wall proteins such as adhesins (ece1Δ,hwp1Δ, andals3Δ) and yeast-locked mutants (clb2Δ,hgc1Δ,cph1Δ,efg1Δ, andefg1Δcph1Δ), was similar to that observed for wild-typeC. albicans. Killing of macrophages was abrogated in hypha-deficient strains, significantly reduced in all glycosylation mutants, and comparable to wild type in cell wall protein mutants. The diminished ability of glycosylation mutants to kill macrophages was not a consequence of impaired hyphal formation within macrophage phagosomes. Therefore, cell wall composition and the ability to undergo yeast-hypha morphogenesis are critical determinants of the macrophage's ability to ingest and processC. albicans.

The disposal of unwanted or dying cells is a key biological process driven by the display of 'eat me' signals that are recognised by phagocytes. Although these markers for uptake are known to include certain lipids and proteins, the role of glycans, which are abundant on cell surfaces, remains poorly characterized. Here, an unbiased glycomic survey by mass spectroscopic analyses of glycosidase (PNGase F) digested human red blood cell (RBC) membranes identified novel N-linked high mannose structures, which are sequestered inside healthy cells with spectrin, the major protein of the internal membrane skeleton, but exteriorised when cells are damaged as a dominant signal for uptake by macrophages. A panel of lectin probes was used to demonstrate that the mannose species were available as discrete patches on the surface of RBC that had been stressed by oxidation, but undetectable on unpermeabilized untreated cells. High mannoses co-localized with alpha-spectrin on lectin/Western blots and this signal was degraded by prior incubation with glycosidases. Super resolution microscopy showed co-localisation of mannose with spectrin in membrane protrusions of oxidized RBC. Co-localization of spectrin with N-linked mannose and exteriorisation on effete cells were also observed in nucleated cells. The mannose displayed on oxidized RBC represents a novel 'eat-me' signal for human cells, since congeners of mannose inhibited uptake by human monocyte-derived macrophages. The mannose receptor (CD206) was identified as an important receptor in this system by the use of blocking antibody and siRNA mediated knock-down. The mechanisms underlying the hemolysis characteristic of sickle cell disease (SCD) remain to be fully defined. We therefore investigated the contribution of this new pathway. RBC from patients with SCD demonstrated remarkably high levels of surface mannose, and super resolution microscopy showed the expression again to be limited to discrete patches and co-localized with spectrin in a disrupted membrane skeletal structure. The importance of mannose exposure to uptake of sickle cells by macrophages was confirmed by inhibition by congeners of mannose and blocking antibody to CD206. The prevalence of SCD is high because of selective pressure caused by the resistance of subjects with sickle cell trait to malarial parasites, which are mainly cleared by splenic macrophages. We therefore investigated whether RBC from subjects with sickle cell trait expressed surface mannose. We show that such RBC express modestly raised levels (p We also investigated whether the degree of mannose exposure correlated with peripheral blood count parameters. The Pearson correlation coefficients of log transformed surface mannose expression with hemoglobin levels, red cell counts and reticulocyte counts were -0.83, -0.84 and 0.73 respectively (all p values In summary, our results reveal a previously undescribed cryptic mannose exteriorization pathway, which mediates disposal of oxidatively damaged cells. The pathway is constitutively activated in SCD, where it mediates haemolysis and the degree of activation correlates well with clinical phenotypes of SCD and sickle cell trait. It thus represents a new mechanism for possible future therapeutic intervention. Disclosures Vickers: University of Aberdeen: Patents & Royalties: About to apply for patent. Barker: University of Aberdeen: Employment, Patents & Royalties: About to apply for patent. Cao: University of Aberdeen: Patents & Royalties: About to apply for patent.

Autoimmune haemolytic anaemia (AIHA) is characterised by the production of autoantibodies that target determinants on red blood cells. Current treatments rely on generalised immunosupression or cytotoxic treatments that may have potentially harmful side effects. Whilst the underlying cause of disease remains unknown, recent advances in our understanding of CD4+ helper T cell (Th) subsets that drive and control the autoimmune response have important implications for the development of novel immunotherapy. The effector arm of the adaptive immune response is now known to include at least three Th subsets: Th1, Th2 and the recently described Th17. In human AIHA, the targets of the autoimmune response in most patients, the Rhesus (Rh) proteins, have been identified and sequenced, providing the opportunity to study antigen specific responses. The effector Th response is dominated by Th1 cells that are under the control of IL-10 dependent regulatory cells (Tr1). These Th1 responses can be suppressed, with synthetic peptides that are recognised by the Tr1 cells. Such specificity would provide an extremely potent tool in the treatment of autoimmune disease. This review discusses the recent advances in our understanding of helper T cell subsets and the implications for the development of specific immunotherapy in autoimmune disease, using the well characterised responses in AIHA as an example.

Atherosclerosis is now recognised as a chronic inflammatory disease occurring within the artery wall and ultimately responsible for myocardial infarction, stroke and peripheral vascular disease. A crucial step in atherogenesis is the infiltration of monocytes into the subendothelial space of large arteries where they differentiate into macrophages and become functionally active. Macrophage accumulation within plaques is a hallmark of all stages of atherosclerosis, indeed recent studies have shown their presence has the potential to act as a non-invasive marker of disease activity and plaque stability. Activated macrophages are major players in all stages of lesion development. They not only accumulate lipids but also express effector molecules that are pro-inflammatory, cytotoxic and chemotactic. Furthermore, they secrete enzymes that degrade extracellular matrix leading to plaque destabilisation and increased risk of rupture. However, macrophages are heterogeneous and when appropriately activated they have the potential to drive tissue remodelling and ultimately vascular repair. Pharmacological modulation of macrophage activities therefore represents an important strategy for the prevention and treatment of atherosclerosis and other inflammatory diseases. The aim of this review is to give a brief overview of our current understanding of macrophage activation, distribution and function within inflamed tissue. This will provide the basis for highlighting already available and future methods to exploit specifically activated macrophages as diagnostic and therapeutic targets for atherosclerosis.

Autoreactive T cells in patients with Goodpasture's disease are specific for epitopes in the Goodpasture antigen (the NC1 domain of the alpha3 chain of type IV collagen) that are rapidly destroyed during antigen processing to a degree that diminishes their presentation to T cells. We hypothesized that patients' autoreactive T cells exist because antigen processing prevents presentation of the self-epitopes they recognize, circumventing specific tolerance mechanisms. We predicted that autoreactive T cells specific for these peptides should also exist in healthy individuals, albeit at low frequency and in an unprimed state. We obtained blood from healthy unrelated donors and, using a panel of 45 alpha3(IV)NC1 peptides, identified alpha3(IV)NC1-specific T cells in all donors. Thirty-six of 45 peptides elicited a proliferative T cell response from at least one subject, and 6 of the peptides evoked a response in >50% of the individuals. This consistency was not caused by selectivity of HLA class II molecules because the donors expressed a diversity of HLA antigens, but was largely a result of the substrate-specificity of the endosomal proteases Cathepsin D and E. There was a significant correlation between high susceptibility to Cathepsin D digestion and the capacity to stimulate primary T cell responses (P = 0.00006). In summary, healthy individuals have low frequencies of unstimulated alpha3(IV)NC1-reactive T cells with similar specificities to the autoreactive T cells found in patients with Goodpasture disease. In both cases, existence of the alpha3(IV)NC1-reactive T cells can be accounted for by destructive processing.

Immunotherapy offers the potential for cure of malignancy without the side effects too commonly seen with conventional chemotherapy. The efficacy of allogenic transplantation and monoclonal antibodies in hematological malignancies illustrate this principle and are now part of routine care. Newer cell based and molecular approaches aimed at stimulating cytotoxic activity against host derived tumor associated antigens are able to ‘boost’ anti-tumor immunity as judged by immunological assays in vitro . Although clinically meaningful responses were originally less evident, more promising results are now being reported. Our growing understanding of tumor immunology provide rationales for further improvements in the field.

Summary Primary infection with Epstein–Barr virus (EBV) in childhood is usually asymptomatic, whereas infection in adolescence may result in infectious mononucleosis (IM) often followed by a fatigue syndrome. EBV latent membrane protein 1 (LMP1) is expressed in latency and in many EBV-associated tumours, including non-Hodgkin lymphoma (NHL). Given the regulatory nature of the CD4+ T-cell response against LMP1 previously reported in healthy donors, we investigated whether patients with active EBV-driven disease can nevertheless mount effector [T-helper cell, type 1 (Th1)] anti-LMP1 responses. We therefore performed a longitudinal study of the nature of CD4+ T-cell responses to LMP1 in four patients with IM, and five patients with NHL. In both groups, responses changed with time. During symptomatic infection or active tumour growth, responses were dominated by a Th1 effector phenotype, but switched to a regulatory interleukin-10 response upon recovery. In addition, the fine specificities of the T cells driving these responses evolved. This study showed the dynamic nature of CD4+ T-cell responses to LMP1, and demonstrated that, although patients can mount Th1 effector responses, recovery from IM and NHL is associated with regulatory responses.

Macrophages are key cells in inflammation and repair, and their activity requires close regulation. The characterization of cues coordinating macrophage function has focused on biologic and soluble mediators, with little known about their responses to physical stimuli, such as the electrical fields that are generated naturally in injured tissue and which accelerate wound healing. To address this gap in understanding, we tested how properties of human monocyte-derived macrophages are regulated by applied electrical fields, similar in strengths to those established naturally. With the use of live-cell video microscopy, we show that macrophage migration is directed anodally by electrical fields as low as 5 mV/mm and is electrical field strength dependent, with effects peaking ∼300 mV/mm. Monocytes, as macrophage precursors, migrate in the opposite, cathodal direction. Strikingly, we show for the first time that electrical fields significantly enhance macrophage phagocytic uptake of a variety of targets, including carboxylate beads, apoptotic neutrophils, and the nominal opportunist pathogen Candida albicans, which engage different classes of surface receptors. These electrical field-induced functional changes are accompanied by clustering of phagocytic receptors, enhanced PI3K and ERK activation, mobilization of intracellular calcium, and actin polarization. Electrical fields also modulate cytokine production selectively and can augment some effects of conventional polarizing stimuli on cytokine secretion. Taken together, electrical signals have been identified as major contributors to the coordination and regulation of important human macrophage functions, including those essential for microbial clearance and healing. Our results open up a new area of research into effects of naturally occurring and clinically applied electrical fields in conditions where macrophage activity is critical.

Summary Although it is widely believed that interleukin (IL)-27 is anti-inflammatory, its role in controlling human immune responses is not fully established. In particular, its interactions with T helper type 17 (Th)17 cytokines are unclear. Our aims were to establish the relationships between IL-27 and proinflammatory cytokines, including IL-17A, in human sera and cultures of peripheral blood mononuclear cells. Plasma IL-27 levels in 879 healthy humans from 163 families varied widely, but with relatively low heritability (19%). Despite IL-27 including a subunit encoded by Epstein–Barr virus-induced gene 3 (EBI3), there was no correlation of levels with serological evidence of infection with the virus. Although IL-27 has been reported to inhibit IL-17A production, we demonstrated a strong positive correlation in sera, but lower correlations of IL-27 with other proinflammatory cytokines. We verified that IL-27 inhibited IL-17A production by human peripheral blood T cells in vitro, but not that it stimulated IL-10 secretion. Importantly, addition of IL-17A decreased IL-27 production by stimulated T cells but had the opposite effect on resting T cells. Together, these data suggest a model whereby IL-27 and IL-17A exerts complex reciprocal effects to boost inflammatory responses, but restrain resting cells to prevent inappropriate activation.

Chronic lymphocytic leukemia (CLL) is frequently associated with autoimmune diseases directed against constituents of the blood, including hemolytic anemia (AIHA). We hypothesized that CLL cells predispose to hematologic autoimmunity by acting as aberrant antigen-presenting cells (APCs). Initially, it was confirmed that all studied patients with AIHA secondary to CLL harbored activated helper T (TH) cells specific for epitopes on the dominant red blood cell (RBC) autoantigens in primary AIHA, the Rh proteins. Rh-specific TH cells were also detected in a number of patients with CLL who, although they did not have AIHA, had low levels of anti-RBC antibody in their sera. Fractionation of putative APC populations from the peripheral blood of patients by negative selection showed that CD5+ CLL cells are the most effective cell type in processing and presenting purified Rh protein to autoreactive TH cells. This ability was confirmed using positively selected CD5+ CLL cells. Thus, our study provides the first evidence for malignant cells driving an autoimmune response by acting as aberrant APCs.

Viruses exploit a number of strategies to evade immune recognition. In this study, we describe a novel mechanism by which EBV, rather than avoiding detection, subverts the immune response by stimulating regulatory T cells that secrete IL-10. Human PBMC from all EBV-seropositive, but not -seronegative, donors responded to both purified latent membrane protein 1 and the corresponding immunodominant peptides with high levels of IL-10 secretion by CD4+ T cells. These IL-10 responses, characteristic of T regulatory 1 cells, inhibited T cell proliferation and IFN-γ secretion induced by both mitogen and recall Ag. It was confirmed that the inhibition was IL-10 dependent by the use of neutralizing Ab. The deviation of the immune response toward suppression is likely to be important in maintaining latency and EBV-associated tumors.

Regulatory T cells have been shown to control animal models of immune-mediated pathology by inhibitory cytokine production, but little is known about such cells in human disease. Here we characterize regulatory T-cell responses specific for a human red blood cell autoantigen in patients with warm-type autoimmune hemolytic anemia. Peripheral blood mononuclear cells from patients with autoimmune hemolytic anemia were found either to proliferate and produce interferon-γ or to secrete the regulatory cytokine interleukin 10 when stimulated in vitro with a major red blood cell autoantigen, the RhD protein. Flow cytometric analysis confirmed that the majority of the responding cells were of the CD4+phenotype. Serial results from individual patients demonstrated that this bias toward proliferative or interleukin-10 responses was unstable over time and could reverse in subsequent samples. Epitope mapping studies identified peptides from the sequence of the autoantigen that preferentially induced interleukin-10 production, rather than proliferation, and demonstrated that many contain naturally processed epitopes. Responses to such peptides suppressed T-cell proliferation against the RhD protein, an inhibition that was mediated largely by interleukin 10 and dependent on cytotonic T lymphocyte–associated antigen (CTLA-4) costimulation. Antigenic peptides with the ability to stimulate specific regulatory cells may represent a new class of therapeutic agents for immune-mediated disease.