Monocyte response to LPS after exposure to corticosteroids and chloroquine with implications for systemic lupus erythematosus

Development of monoclonal antibodies for quantification of bovine tumor necrosis factor-α

The expression of the proinflammatory cytokine tumor necrosis factor-α (TNF-α) is associated with production losses in dairy cows and is a hallmark of early inflammatory processes. Reliable tools for the detection and quantification of soluble as well as cytoplasmatic bovine TNF-α are needed to deepen our understanding of inflammatory dynamics in dairy cows. The objective of this study was to generate a monoclonal antibody (mAb) pair that could be used to quantify bovine TNF-α in cell culture supernatants and plasma and to detect cytoplasmatic TNF-α in bovine leukocyte populations. One mouse was immunized with a recombinant fusion protein of bovine TNF-α and equine IL-4 generated in Chinese hamster ovary cells. Murine monoclonal antibodies specific to bovine TNF-α were produced in hybridoma cell lines and selected based on their specificity to the recombinant IL-4/TNF-α protein. Clones 197-1 and 65-2, both murine IgG1 isotypes, detected the bovine TNF-α fusion protein as well as the native protein produced by peripheral blood mononuclear cells (PBMC) stimulated with a combination of phorbol myristate acetate and ionomycin. Both mAbs were tested for and lacked cross-reactivity to equine IL-4 and 3 other recombinant bovine cytokines (IFN-γ, IL-10, and CCL5) and were used to develop a fluorescent bead-based assay. The range of bovine TNF-α detection in the assay was 0.2 to 620 ng/mL, and the test was used to quantify native bovine TNF-α in cell culture supernatants of stimulated PBMC and in plasma from ex vivo whole-blood stimulations. Sample matrices were spiked with TNF-α, with subsequent recovery rates (mean ± SD) of 89% ± 9 (n = 3) in culture medium and 94% ± 12 (n = 3) in heat-inactivated fetal bovine serum. Serial dilutions of plasma and cell culture supernatants from stimulated whole blood or PBMC indicated excellent accuracy for quantification of native TNF-α in bovine samples. Both bovine TNF-α mAbs also detected intracellular TNF-α in bovine CD14⁺ monocytes and CD4⁺/CD8⁺ lymphocytes. In conclusion, we demonstrated that the mAbs generated provide valuable new tools to quantify native bovine TNF-α in a wide concentration range and to characterize intracellular TNF-α expression in bovine leukocytes.

New mAbs facilitate quantification of secreted equine TNF-α and flow cytometric analysis in monocytes and T cells

Tumor necrosis factor-α (TNF-α) is a pleiotropic cytokine, that is involved in acute inflammation and is employed as a biomarker of inflammatory diseases in several species for which reliable quantification is available. We aimed to develop suitable tools to quantify TNF-α in equine samples. We generated two new mAbs against equine TNF-α (clones 48 and 292), evaluated their specificity for this cytokine, and confirmed detection of native TNF-α in stimulated equine PBMC. The TNF-α mAbs were paired in a fluorescent bead-based assay for quantification of equine TNF-α. The TNF-α assay had a wide quantification range of 12 pg/mL - 38.4 ng/mL. In addition, TNF-α mAb 48 was used for a detailed analysis of TNF-α production in PBMC by intracellular staining and flow cytometry. TNF-α was expressed by CD14⁺ monocytes after LPS stimulation and by monocytes and lymphocytes after polyclonal stimulation with PMA and ionomycin in vitro. TNF-α expressing lymphocytes consisted mainly of CD4⁺ T cells. CD8⁺ T cells and other lymphocytes also expressed TNF-α. The new mAbs evaluated here for soluble and intracellular TNF-α will enable the detailed analysis of this important pro-inflammatory cytokine during equine immune responses and inflammatory diseases of the horse.

Glucocorticoid receptor sensitivity in early pregnancy in an African American cohort

PROBLEM

Disruption in homeostatic feedback loops between inflammatory mediators and the hypothalamic-pituitary-adrenal (HPA) axis is a key mechanism linking chronic stress to inflammation and adverse health outcomes, including those occurring during pregnancy. In particular, alterations in glucocorticoid sensitivity may occur as a result of chronic stress, including that due to racial discrimination, and may be implicated in the persistent adverse maternal and infant health outcomes experienced by African Americans. While there are a few large-scale studies in human pregnancy that measure both cytokines and HPA axis hormones, to our knowledge, none directly measure glucocorticoid sensitivity at the cellular level, especially in an African American population.

METHOD OF STUDY

We measured the full range of the dexamethasone (DEX) dose-response suppression of TNF-α in first-trimester blood samples from 408 African American women and estimated leukocyte cell type contribution to the production of TNF-α.

RESULTS

The mean (SD) DEX level needed to inhibit TNF-α production by 50% (ie, DEX IC50 ) was 9.8 (5.8) nmol/L. Monocytes appeared to be the main driver of Uninhibited TNF-α production, but monocyte counts explained only 14% of the variation. Monocyte counts were only weakly correlated with the DEX IC50 (r = -.11, P < .05). Moreover, there was no statistically significant correlation between the DEX IC50 and circulating pro-inflammatory (CRP, IL-6, IFN-γ) or anti-inflammatory (IL-10) mediators (P > .05).

CONCLUSION

These findings challenge some prior assumptions and position this comprehensive study of glucocorticoid sensitivity as an important anchor point in the growing recognition of interindividual variation in maternal HPA axis regulation and inflammatory responses.

Serum interleukin-6 level is correlated with the disease activity of systemic lupus erythematosus: a meta-analysis

Interleukin-6 (IL-6) plays a crucial role in systemic autoimmunity and pathologic inflammation. Numerous studies have explored serum IL-6 levels in systemic lupus erythematosus (SLE) and their correlation with disease activity. Here, we performed a meta-analysis to quantitatively assess the correlation between the serum IL-6 levels and SLE activity. The PubMed and EMBASE databases were thoroughly searched for relevant studies up to September 2019. Standardized mean differences (SMDs) with 95% confidence intervals (95% CIs) were used to describe the differences between serum IL-6 levels in SLE patients and healthy controls and between those in active SLE patients and inactive SLE patients. The correlation between the serum IL-6 levels and disease activity was evaluated using Fisher's z values. A total of 24 studies involving 1817 SLE patients and 874 healthy controls were included in this meta-analysis. Serum IL-6 levels were significantly higher in SLE patients than in the healthy controls (pooled SMD: 2.12, 95% CI: 1.21-3.03, Active SLE patients had higher serum IL-6 levels than inactive SLE patients (pooled SMD: 2.12, 95% CI: 1.21-3.03). Furthermore, the pooled Fisher's z values (pooled Fisher's z=0.36, 95% CI: 0.26-0.46, p<0.01) showed that there was a positive correlation between the serum IL-6 levels and SLE activity. This study suggested that serum IL-6 levels were higher in patients with SLE than in healthy controls, and they were positively correlated with disease activity when Systemic Lupus Erythematosus Disease Activity Index>4 was defined as active SLE. More homogeneous studies with large sample sizes are warranted to confirm our findings due to several limitations in our meta-analysis.

Reduced TCR Signaling Contributes to Impaired Th17 Responses in Tolerant Kidney Transplant Recipients

BACKGROUND

The development of spontaneous kidney transplant tolerance has been associated with numerous B cell-related immune alterations. We have previously shown that tolerant recipients exhibit reduced B-cell receptor signalling and higher IL-10 production than healthy volunteers. However, it is unclear whether cluster of differentiation (CD)4 T cells from tolerant recipients also display an anti-inflammatory profile that could contribute to graft maintenance.

METHODS

CD4 T cells were isolated from kidney transplant recipients who were identified as being tolerant recipients, patients with chronic rejection or healthy volunteers. CD4 T cells from the 3 groups were compared in terms of their gene expression profile, phenotype, and functionally upon activation.

RESULTS

Gene expression analysis of transcription factors and signalling proteins, in addition to surface proteins expression and cytokine production, revealed that tolerant recipients possessed fewer Th17 cells and exhibited reduced Th17 responses, relative to patients with chronic rejection or healthy volunteers. Furthermore, impaired T-cell receptor signalling and altered cytokine cooperation by monocytes contributed to the development of Th17 cells in tolerant recipients.

CONCLUSIONS

These data suggest that defective proinflammatory Th17 responses may contribute to the prolonged graft survival and stable graft function, which is observed in tolerant recipients in the absence of immunosuppressive agents.

Differential ubiquitination in NETs regulates macrophage responses in systemic lupus erythematosus

OBJECTIVES

To assess if ubiquitinated proteins potentially present in neutrophil extracellular traps (NETs) can modify cellular responses and induce inflammatory mechanisms in patients with systemic lupus erythematosus (SLE) and healthy subjects.

MATERIALS AND METHODS

We studied 74 subjects with SLE and 77 healthy controls. Neutrophils and low-density granulocytes were isolated, and NETs were induced. Ubiquitin content was quantified in NETs by western blot analysis, ELISA and immunofluorescence microscopy, while ubiquitination of NET proteins was assessed by immunoprecipitation. Monocyte-derived macrophages from SLE and controls were isolated and stimulated with NETs or ubiquitin. Calcium flux and cytokine synthesis were measured following these stimuli.

RESULTS

NETs contain ubiquitinated proteins, with a lower expression of polyubiquitinated proteins in subjects with SLE than in controls. Myeloperoxidase (MPO) is present in ubiquitinated form in NETs. Patients with SLE develop antiubiquitinated MPO antibodies, and titres positively correlate with Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) score (P<0.01), and negatively correlate with complement components (P<0.01). Stimulation of monocyte-derived macrophages with NETs or with ubiquitin led to enhanced calcium flux. In addition, stimulation with NETs led to enhanced cytokine (tumour necrosis factor-α and interleukin-10) production in macrophages from patients with SLE when compared with controls, which was hampered by inhibition of NET internalisation by macrophages.

CONCLUSION

This is the first study to find ubiquitinated proteins in NETs, and evidence for adaptive immune responses directed towards ubiquitinated NET proteins in SLE. The distinct differences in ubiquitin species profile in NETs compared with healthy controls may contribute to dampened anti-inflammatory responses observed in SLE. These results also support a role for extracellular ubiquitin in inflammation in SLE.

MIF promotes a differential Th1/Th2/Th17 inflammatory response in human primary cell cultures: Predominance of Th17 cytokine profile in PBMC from healthy subjects and increase of IL-6 and TNF-α in PBMC from active SLE patients

Macrophage migration Inhibitory Factor (MIF) is a cytokine associated with the pathogenesis of autoimmune inflammatory diseases. There is evidence that MIF functions in a positive-feedback-loop with proinflammatory cytokines and could perpetuate the inflammatory process in Systemic Lupus Erythematosus (SLE).The aim of this study was to assess the effect of recombinant-human-MIF (rhMIF) on the expression of Th1, Th2 and Th17 cytokines in Peripheral Blood Mononuclear Cells (PBMC) from Healthy Subjects (HS) and SLE patients. The PBMC were isolated from SLE patients classified according to the 1997 SLE ACR criteria and HS donors; all subjects included were women from an unrelated Mexican-Mestizo population. The PBMC isolated were stimulated with rhMIF, LPS and ISO-1 in different combinations; Th1, Th2 and Th17cytokine profiles levels were determined by MAGPIX Bio-plex assay in supernatants from cell cultures. We observed in supernatants of PBMCs from HS treated with rhMIF a predominance of Th17 cytokine profile with an increase of IL-17A, IL-17F and IL-21 versus PBMCs from SLE patients, which showed an inflammatory profile represented by increase of IL-6 cytokine. According to SLE remission/activity presented at enrollment in the study (Mex-SLEDAI index), the PBMC from active SLE patients showed higher levels of TNF-α and IL-6 versus PBMC from remission SLE patients. In conclusion, our results suggest that MIF can induce a differential inflammatory response in physiological and pathological conditions with a predominance of a Th17 cytokine profile in PBMC from HS and an increase in TNF-α and IL-6 expression in PBMC from active SLE patients.

Single-cell gene expression patterns in lupus monocytes independently indicate disease activity, interferon and therapy

Objectives

Important findings can be masked in gene expression studies of mixed cell populations. We examined single-cell gene expression in SLE patient monocytes in the context of clinical and immunological features.

Methods

Monocytes were purified from patients with SLE and controls, and individually isolated for single-cell gene expression measurement. A panel of monocyte-related transcripts were measured in individual classical (CL) and non-classical (NCL) monocytes.

Results

Analyses of both CL and NCL monocytes demonstrated that many genes had a lower expression rate in SLE monocytes than in controls. Unsupervised hierarchical clustering of the CL and NCL data sets demonstrated independent clusters of cells from the patients with SLE that were related to disease activity, type I interferon (IFN) and medication use. Thus, each of these factors exerted a different impact on monocyte gene expression that could be identified separately, and a number of genes correlated uniquely with disease activity. We found within-cell correlations between genes directly induced by type I IFN-induced and other non–IFN-induced genes, suggesting the downstream biological effects of type I IFN in individual human SLE monocytes which differed between CLs and NCLs.

Conclusions

In summary, single-cell gene expression in monocytes was associated with a wide range of clinical and biological features in SLE, providing much greater detail and insight into the cellular biology underlying the disease than previous mixed-cell population studies.

Evaluation of the immunomodulatory effect of melatonin on the T-cell response in peripheral blood from systemic lupus erythematosus patients

Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by the production of antinuclear autoantibodies. In addition, the involvement of CD4+ T-helper (Th) cells in SLE has become increasingly evident. Although the role of melatonin has been tested in some experimental models of lupus with inconclusive results, there are no studies evaluating the melatonin effect on cells from patients with SLE. Therefore, the aim of this study was to analyse the role of in vitro administered melatonin in the immune response of peripheral leukocytes from treated patients with SLE (n = 20) and age- and sex-matched healthy controls. Melatonin was tested for its effect on the production of key Th1, Th2, Th9, Th17 and innate cytokines. The frequency of T regulatory (Treg) cells and the expression of FOXP3 and BAFF were also explored. Our results are the first to show that melatonin decreased the production of IL-5 and to describe the novel role of melatonin in IL-9 production by human circulating cells. Additionally, we highlighted a two-faceted melatonin effect. Although it acted as a prototypical anti-inflammatory compound, reducing exacerbated Th1 and innate responses in PHA-stimulated cells from healthy subjects, it caused the opposite actions in immune-depressed cells from patients with SLE. Melatonin also increased the number of Treg cells expressing FOXP3 and offset BAFF overexpression in SLE patient cells. These findings open a new field of research in lupus that could lead to the use of melatonin as treatment or cotreatment for SLE.

Sex Differences in monocytes and TLR4 associated immune responses; implications for systemic lupus erythematosus (SLE)

It has been shown that TLR7 and TLR9 signaling play a role in SLE pathogenesis. Our recent study revealed that estrogen receptor α knockout mice have impaired inflammatory responses to TLR3, TLR4, TLR7 and TLR9 ligand stimulation in DCs, B cells and whole spleen cells. These findings indicate that estrogen receptor mediated signaling may impact universal TLR responsiveness. Whether estrogen has a direct or indirect effect on TLR responsiveness by immune cells is not clear. There is evidence of a role of TLR4 in SLE disease pathogenesis, such as the kidney damage, the induction of CD40 and autoantibodies, the suppression of regulatory T cells, and the role of pro-inflammatory cytokines (e.g., IL-6, IL-1β, TNF-α) in SLE pathogenesis that can be induced by TLR4-mediated monocyte activation, suggesting that TLR4 and TLR4 responsiveness are also important for SLE disease. This review will focus on TLR4 responses and monocytes, which are understudied in systemic autoimmune diseases such as SLE.

The immune consequences of preterm birth

Preterm birth occurs in 11% of live births globally and accounts for 35% of all newborn deaths. Preterm newborns have immature immune systems, with reduced innate and adaptive immunity; their immune systems may be further compromised by various factors associated with preterm birth. The immune systems of preterm infants have a smaller pool of monocytes and neutrophils, impaired ability of these cells to kill pathogens, and lower production of cytokines which limits T cell activation and reduces the ability to fight bacteria and detect viruses in cells, compared to term infants. Intrauterine inflammation is a major contributor to preterm birth, and causes premature immune activation and cytokine production. This can induce immune tolerance leading to reduced newborn immune function. Intrauterine inflammation is associated with an increased risk of early-onset sepsis and likely has long-term adverse immune consequences. Requisite medical interventions further impact on immune development and function. Antenatal corticosteroid treatment to prevent newborn respiratory disease is routine but may be immunosuppressive, and has been associated with febrile responses, reductions in lymphocyte proliferation and cytokine production, and increased risk of infection. Invasive medical procedures result in an increased risk of late-onset sepsis. Respiratory support can cause chronic inflammatory lung disease associated with increased risk of long-term morbidity. Colonization of the infant by microorganisms at birth is a significant contributor to the establishment of the microbiome. Caesarean section affects infant colonization, potentially contributing to lifelong immune function and well-being. Several factors associated with preterm birth alter immune function. A better understanding of perinatal modification of the preterm immune system will allow for the refinement of care to minimize lifelong adverse immune consequences.

Inhibition of aberrant circulating Tfh cell proportions by corticosteroids in patients with systemic lupus erythematosus

OBJECTIVE

To observe the proportion of peripheral T follicular helper (Tfh) cells in patients with systemic lupus erythematosus (SLE) and to assess the role of steroids on Tfh cells from SLE patients.

METHODS

Peripheral blood mononuclear cells (PBMCs) from 42 SLE patients and 22 matched healthy subjects were collected to assess proportions of circulating CXCR5(+)PD1(+)/CD4(+) T cells (Tfh), CD4(+)CCR6(+) T cells (Th17-like) and CD19(+)CD138(+) plasma cells by flow cytometry. 8 of the patients had their blood redrawn within one week after receiving methylprednisolone pulse treatment. Disease activity was evaluated by SLE disease activity index. To test the effect of IL-21 and corticosteroids on Tfh cells in vitro, PBMCs harvested from another 15 SLE patients were cultured with medium, IL-21, or IL-21+ dexamethasone for 24 hours and 72 hours. PBMCs from an independent 23 SLE patients were cultured with different concentrations of dexamethasone for 24 hours.

RESULTS

Compared to normal controls, percentages of circulating Tfh cells, but not Th17 cells, were elevated in SLE patients and correlated with disease activity. Proportions of Tfh cells in SLE patients were positively correlated with those of plasma cells and serum levels of antinuclear antibodies. After methylprednisolone pulse treatment, both percentages and absolute numbers of circulating Tfh cells were significantly decreased. In vitro cultures showed an increase of Tfh cell proportion after IL-21 stimulation that was totally abolished by the addition of dexamethasone. Both 0.5 and 1 µM dexamethasone decreased Tfh cells dose dependently (overall p = 0.013).

CONCLUSIONS

We demonstrated that elevated circulating Tfh cell proportions in SLE patients correlated with their disease activities, and circulating levels of plasma cells and ANA. Corticosteroids treatment down-regulated aberrant circulating Tfh cell proportions both in vivo and in vitro, making Tfh cells a new treatment target for SLE patients.

Antimalarial drug chloroquine counteracts activation of indoleamine (2,3)-dioxygenase activity in human PBMC

Antimalarial chloroquine is also used for the treatment of immune-mediated diseases. The interference of chloroquine with interferon-γ-induced tryptophan breakdown and neopterin production has been investigated in human peripheral blood mononuclear cells (PBMC) in vitro. Micromolar concentrations (2–50 μM) of chloroquine dose-dependently suppressed mitogen-induced tryptophan breakdown in PBMC but not in the myelomonocytic THP-1-Blue cell line, after 48 h of treatment. In stimulated PBMC, neopterin production was super-induced by 10 μM chloroquine, while it was significantly suppressed at a concentration of 50 μM. These anti-inflammatory effects may relate to the therapeutic benefit of chloroquine in inflammatory conditions and may widen the spectrum of its clinical applications.