Interleukin 18 and interleukin 18 binding protein in patients with idiopathic thrombocytopenic purpura

Novel Biomarkers for Diagnosis and Monitoring of Immune Thrombocytopenia

Lower-than-normal platelet counts are a hallmark of the acquired autoimmune illness known as immune thrombocytopenia, which can affect both adults and children. Immune thrombocytopenia patients' care has evolved significantly in recent years, but the disease's diagnosis has not, and it is still only clinically achievable with the elimination of other causes of thrombocytopenia. The lack of a valid biomarker or gold-standard diagnostic test, despite ongoing efforts to find one, adds to the high rate of disease misdiagnosis. However, in recent years, several studies have helped to elucidate a number of features of the disease's etiology, highlighting how the platelet loss is not only caused by an increase in peripheral platelet destruction but also involves a number of humoral and cellular immune system effectors. This made it possible to identify the role of immune-activating substances such cytokines and chemokines, complement, non-coding genetic material, the microbiome, and gene mutations. Furthermore, platelet and megakaryocyte immaturity indices have been emphasized as new disease markers, and prognostic signs and responses to particular types of therapy have been suggested. Our review's goal was to compile information from the literature on novel immune thrombocytopenia biomarkers, markers that will help us improve the management of these patients.

Dysregulated expression of miRNAs in immune thrombocytopenia

In recent years the critical role of miRNAs has been established in many diseases, including autoimmune disorders. Immune thrombocytopenia purpura (ITP) is a predominant autoimmune disease, in which aberrant expression of miRNAs has been observed, suggesting that miRNAs are involved in its development. miRNAs could induce an imbalance in the T helper (Th)1/Th2 cell and Th17/Treg cell-related responses. Moreover, they could also cause alterations in Th9 and Th22 cell responses, and activate Tfh (T follicular helper) cell-dependent auto-reactive B cells, thus influencing megakaryogenesis. Herein, we summarize the role of immune-related miRNAs in ITP pathogenesis, and look forward to clinical applications.

Interleukin (IL)-1 family cytokines could differentiate primary immune thrombocytopenia from systemic lupus erythematosus-associated thrombocytopenia

Background

Primary immune thrombocytopenia (ITP) is an autoimmune-mediated disorder characterized by a decreased platelet count. Systemic lupus erythematosus (SLE) is also an autoimmune disease in which thrombocytopenia is a common hematologic manifestation. Interleukin (IL)-1 family cytokines are major proinflammatory and immunoregulatory mediators. This study aimed to investigate the role of IL-1 cytokines in patients with ITP and SLE and the potential pathophysiologic mechanism to differentiate SLE-associated thrombocytopenia (SLE-TP) from ITP.

Methods

Multiplex cytokine assay and real-time polymerase chain reaction (RT-PCR) were used to measure IL-1 cytokines in 17 newly diagnosed ITP patients, 17 SLE-TP patients, 19 SLE patients without thrombocytopenia (SLE-NTP), and 10 healthy controls.

Results

The serum levels of IL-1β, IL-18, IL-36α, IL-36β, IL-36γ, and IL-33 were decreased significantly in ITP patients compared with SLE-TP patients, SLE-NTP patients, and healthy controls (P<0.05). While there was no significant difference in the serum level of IL-37 between ITP and SLE-TP patients, there was a positive correlation between the platelet count and IL-37 level in ITP patients. Our data suggested that serum IL-1β, IL-18, IL-36α, IL-36β, IL-36γ, IL-33, and IL-37 could be considered biomarkers in the diagnosis of ITP.

Conclusions

Serum IL-1β, IL-18, IL-36α, IL-36β, IL-36γ, and IL-33 could be considered biomarkers to differentiate SLE-TP from ITP patients.

Interleukin-18 and Hematopoietic Recovery after Allogeneic Stem Cell Transplantation

Simple Summary

We have previously shown that high pre-conditioning levels of Interleukin-18 were associated with worse survival after allogeneic stem cell transplantation due to increased non-relapse mortality. While no correlations with acute graft-versus-host disease were observed, interleukin-18-related excess mortality was mainly driven by fatal infectious complications. In multiple studies, delayed hematopoietic recovery and poor graft function following allogeneic stem cell transplantation has been demonstrated as a powerful predictor of non-relapse mortality. The present study links high interleukin-18 to delayed platelet recovery in allografted patients. Given the functions of interleukin-18 in regulating the quiescence of hematopoietic stem/progenitor cells, our findings may be explained by Interferon gamma-independent inhibitory effects of interleukin-18 on stem cell proliferation and hematopoietic reconstitution in allografted patients. Importantly, considering recent successful interleukin-18-neutralizing approaches in autoimmune disorders, our results provide a rationale to explore modulation of interleukin-18 for improving hematopoietic recovery and outcomes in allogeneic stem cell transplantation recipients.

Abstract

Interleukin-18 (IL-18) is an immunoregulatory cytokine and a context-dependent regulator of hematopoietic stem/progenitor cell (HSPC) quiescence in murine models. In a previous study, high pre-conditioning levels of IL-18 were associated with increased non-relapse mortality (NRM) after allogeneic stem cell transplantation (alloSCT). To investigate the clinical impact of IL-18 status on hematopoietic function, the associations of pre-conditioning and day 0–3 cytokine levels with platelet and neutrophil recovery were analyzed in a training cohort of 714 allografted patients. In adjusted logistic regression analyses, both increasing pre-conditioning and day 0–3 IL-18 levels had a significantly higher adjusted odds ratio (aOR) of delayed platelet and neutrophil recovery on day +28 post-transplant (aOR per two-fold increase: 1.6–2.0). The adverse impact of high pre-conditioning IL-18 on day +28 platelet recovery was verified in an independent cohort of 673 allografted patients (aOR per two-fold increase: 1.8 and 1.7 for total and free IL-18, respectively). In both cohorts, a platelet count ≤20/nL on day +28 was associated with a significantly increased hazard of NRM (hazard ratio 2.13 and 2.94, respectively). Our findings support the hypothesis that elevated peritransplant IL-18 levels affect post-transplant HSPC function and may provide a rationale to explore modulation of IL-18 for improving alloSCT outcomes.

Rapamycin induces megakaryocytic differentiation through increasing autophagy in Dami cells

: Autophagy is a conserved cellular process that involves the degradation of cytoplasmic components in eukaryotic cells. However, the correlation between autophagy and megakaryocyte development is unclear. This study aims to explore the role of autophagy in megakaryocyte differentiation. To test our hypothesis, we used the Dami cell line in-vitro experiments. Rapamycin and Bafilomycin A1 were used to stimulate Dami cells. CD41 expression and apoptosis were analysed by flow cytometry. Autophagy-related proteins were detected by Western blotting. 12-O-Tetradecanoylphorbol 13-acetate-treated Dami cells can simulate endomitosis of megakaryocytes in vitro. Rapamycin-induced autophagic cell death was verified by LC3-II conversion upregulation. Meanwhile, Bafilomycin A1 blocked endomitosis and autophagy of Dami cells. Our results provide evidence that autophagy is involved in megakaryocyte endomitosis and platelet development. Rapamycin inhibited cell viability and induced multiple cellular events, including apoptosis, autophagic cell death, and megakaryocytic differentiation, in human Dami cells. Upregulated autophagy triggered by rapamycin can promote the differentiation of Dami cells, while endomitosis is accompanied by enhanced autophagy.

Disrupted balance of CD4+ T-cell subsets in bone marrow of patients with primary immune thrombocytopenia

Disequilibrium of CD4⁺ T-cell subpopulations in peripheral blood (PB) of patients with primary immune thrombocytopenia (ITP) has been well established, whereas the profile of CD4⁺ T-cell subpopulations in bone marrow (BM) remains elusive. In the present study, the frequencies of T helper 22 (Th22), Th17, Th1, Th2, follicular T helper (Tfh) cells and regulatory T cells (Tregs) as well as their effector cytokines in BM and PB from active ITP patients and healthy controls (HCs) were determined. Results showed that the frequencies of Th22, Th17, Th1, and Tfh cells were significantly higher, but Treg number was remarkably lower in BM from ITP patients than from HCs. In the ITP group, it was notable that the numbers of BM Th22, Th17, Th1, Th2, and Tfh cells were significantly elevated compared with the matched PB counterparts, while Treg number in BM was considerably reduced compared with that in PB. In consistence with the BM Th subset pattern, plasma levels of interleukin (IL)-22, IL-17A, and interferon (INF)-γ in BM from ITP patients were significantly increased compared with that from HCs. Therefore, the balance of CD4⁺ T-cell subsets was disrupted in both BM and PB of ITP patients, suggesting that this might play important roles in the pathophysiological process of ITP.

High-Dose Dexamethasone Alters the Increase in Interleukin-16 Level in Adult Immune Thrombocytopenia

Adult primary immune thrombocytopenia (ITP) is an autoimmune-mediated haemorrhagic disorder. Interleukin-16 (IL-16) can directly affect cellular or humoural immunity by mediating the cellular cross-talk among T cells, B cells and dendritic cells. Several studies have focused on IL-16 as an immunomodulatory cytokine that takes part in Th1 polarization in autoimmune diseases. In this study, we investigated IL-16 expression in the bone marrow supernatant and plasma of ITP patients and healthy controls. What's more, we detected IL-16 expression in ITP patients with the single-agent 4-day high-dose dexamethasone (HD-DXM) therapy. In patients with active ITP, bone marrow supernatant and plasma IL-16 levels increased (P < 0.05) compared with those of healthy controls. In the meantime, the mRNA expression in BMMCs (pro-IL-16, caspase-3) and PBMCs (pro-IL-16, caspase-3 and T-bet) of ITP patients was increased (P < 0.05) relative to those of healthy controls. In patients who responded to HD-DXM therapy, both plasma IL-16 levels and gene expression in PBMCs (pro-IL-16, caspase-3, and T-bet) were decreased (P < 0.05). In summary, the abnormal level of IL-16 plays important roles in the pathogenesis of ITP. Regulating Th1 polarization associated with IL-16 by HD-DXM therapy may provide a novel insight for immune modulation in ITP.

Interleukin-18 plays a dispensable role in murine and likely also human bone marrow failure

Interleukin-18 (IL-18), also known as interferon-gamma (IFN-γ)-inducing factor, is involved in Th1 responses and regulation of immunity. Accumulating evidence implicates IL-18 in autoimmune diseases, but little is known of its role in acquired aplastic anemia (AA), the immune-mediated destruction of bone marrow (BM) hematopoietic stem and progenitor cells (HSPCs). IL-18 protein levels were significantly elevated in sera of severe AA (SAA) patients, including both responders and nonresponders assayed before treatment, and decreased after treatment. IL-18 receptor (IL-18R) was expressed on HSPCs. Co-culture of human BM CD34⁺ cells from healthy donors with IL-18 upregulated genes in the helper T-cell and Notch signaling pathways and downregulated genes in the cell cycle regulation, telomerase, and IL-6 signaling pathways. Plasma IL-18 levels were also elevated in murine models of immune-mediated BM failure. However, deletion of IL-18 in donor lymph node cells or deletions of either IL-18 or IL-18R in recipients did not attenuate elevations of circulating IFN-γ, tumor necrosis factor-alpha, or IL-6, nor did they alleviate BM failure. In summary, our findings suggest that, although increased circulating IL-18 is a feature of SAA, it may reflect an aberrant immune response but be dispensable to the pathogenesis of AA.

IL-1 family cytokines and soluble receptors in systemic lupus erythematosus

Background

Dysregulated production of cytokines has a critical role in systemic lupus. The aim of this work is to identify, by a comprehensive analysis of IL-1 family cytokines and receptors in serum, correlation between cytokines/receptors’ levels and the clinical and serological features of the disease.

Methods

A full clinical evaluation was performed in 74 patients with systemic lupus erythematosus (SLE). C3, C4, anti-dsDNA and anti-C1q antibodies were measured. Cytokines of the IL-1 family (IL-1α, IL-1β, IL-33, IL-18), soluble receptors (sIL-1R1, sIL-1R2, sIL-1R3, ST2/sIL-1R4) and antagonists (IL-1Ra, IL-18 binding protein (IL-18BP)) were measured in serum by multiarray ELISA. Free IL-18 was calculated as the amount of IL-18 not inhibited by IL-18BP. Data were analysed by non-parametric tests and by multivariate analysis, using partial least squares (PLS) models.

Results

Total IL-18, IL-18BP, sIL-1R4 and IL-1Ra levels were higher in SLE vs. controls. Total and free IL-18 and sIL-1R4 were higher in patients with active vs. inactive disease and correlated with ECLAM, anti-C1q and anti-dsDNA antibodies. sIL-1R2 was higher in patients with inactive disease, was negatively correlated with ECLAM and anti-C1q antibodies and was positively correlated with C3 levels. PLS identified sIL-1R4, sIL-1R2 and anti-dsDNA as variables distinguishing patients with active from those with inactive disease; sIL-1R4, IL-18BP and anti-dsDNA identified patients with active nephritis; sIL-1R4, C3, IL-18 and free IL-18 identified patients with haematological involvement.

Conclusion

The data support the use of IL-18, sIL-1R2 and sIL-1R4 as biomarkers of disease activity and organ involvement, and suggest that failure in the inhibition of IL-1 activation may be a critical event in the active stages of SLE.

The Role of Proinflammatory Cytokine Interleukin-18 in Radiation Injury

Massive radiation-induced inflammatory factors released from injured cells may cause innate and acquired immune reactions that can further result in stress response signal activity-induced local and systemic damage. IL-1 family members IL-1β, IL-18, and IL-33 play key roles in inflammatory and immune responses and have been recognized to have significant influences on the pathogenesis of diseases. IL-1β, IL-18, and IL-33 share similarities of cytokine biology, but differences exist in signaling pathways. A key component of the inflammatory reaction is the inflammasome, which is a caspase-1-containing multiprotein oligomer. Pathological stimuli such as radiation can induce inflammasome and caspase-1 activation, and subsequently cause maturation (activation) of pro-forms of IL-1 and IL-18 upon caspase-1 cleavage. This caspase-1 dependent and IL-1 and IL-18 associated cell damage is defined as pyroptosis. Activated IL-1 and IL-18 as proinflammatory cytokines drive pathology at different immune and inflammatory disorders through Toll-like receptor (TLR) signaling. While the mechanisms of IL-1β-induced pathophysiology of diseases have been well studied, IL-18 has received less attention. The author recently reported that gamma radiation highly increased IL-1β, IL-18 and IL-33 expression in mouse thymus, spleen and/or bone marrow cells; also circulating IL-18 can be used as a radiation biomarker to track radiation injury in mice, minipigs, and nonhuman primates. This mini-review focuses on the role of IL-18 in response to gamma radiation-induced injury.

Circulating IL-18 Binding Protein (IL-18BP) and IL-18 as Dual Biomarkers of Total-Body Irradiation in Mice

We have previously reported that circulating interleukin-18 (IL-18) can be used as a radiation biomarker in mice, minipigs and nonhuman primates. In this study, we further determined the serum levels of IL-18 binding protein (IL-18BP), a natural endogenous antagonist of IL-18, in CD2F1 mice 1-13 days after total-body gamma irradiation (TBI) with different doses (5-10 Gy). We compared the changes in blood lymphocyte, neutrophil and platelet counts as well as the activation of the proapoptotic executioner caspase-3 and caspase-7, and the expression of the inflammatory factor cyclooxygenase 2 (COX-2) in spleen cells, with the changes of IL-18BP and IL-18 in mouse serum. We also evaluated the significance, sensitivity and specificity of alterations in radiation-induced IL-18BP. IL-18 increased from day 1-13 after TBI in a dose-dependent manner that was paralleled with an increase in IL-18 receptor alpha (IL-18Rα) in irradiated mouse spleen cells. IL-18BP rapidly increased (25-63 fold) in mouse serum on day 1 after different doses of TBI. However, it returned to baseline within 3 days after 5-7 Gy doses and within 7 days after 8 Gy dose, and was unaltered thereafter. In contrast, high doses of radiation (9 and 10 Gy) significantly sustained a higher level of IL-18BP in mouse serum and later induced a second phase of increase in IL-18BP on day 9-13 after irradiation, which coincided with the onset of animal mortality. Consistent with this observation, highly activated caspase-3 and -7 in 8-10 Gy irradiated mouse spleen cells exhibited reduced or no activity 24 h after 5 Gy, although radiation induced an inflammatory response, as shown by COX-2 expression in all irradiated cells. Our data suggest that the radiation-induced differential elevation of IL-18 and IL-18BP in animal serum is a dynamic and discriminative indicator of the severity of injury after exposure to ionizing radiation. These findings support the inclusion of the dual biomarkers IL-18BP and IL-18 in the development of a multifactorial strategy for radiation dose and injury assessment.

Interleukin-18 and miR-130a in severe sepsis patients with thrombocytopenia

BACKGROUND

Thrombocytopenia is one of the most common laboratory abnormalities encountered in patients with severe sepsis. It has been reported that thrombocytopenia is linked to mortality in patients with severe sepsis. However, the mechanism of thrombocytopenia in sepsis is unknown. We hypothesized that inflammatory cytokines and microRNAs (miRNAs) are not only involved in the pathogenesis of sepsis, but also are correlated with thrombocytopenia.

PATIENTS AND METHODS

Eligible patients with severe sepsis were prospectively recruited and treated at our hospital between June 2012 and May 2014. The miRNA and protein expression of interleukin (IL)-18 and IL-27 were detected by real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. The expression of miR-130a and miR-150 was detected by TaqMan real-time polymerase chain reaction.

RESULTS

Sixty eligible patients were divided into two groups: 28 severe sepsis patients with thrombocytopenia and 32 severe sepsis patients without thrombocytopenia. The results demonstrated that the miRNA expression and plasma concentration of IL-18 in severe sepsis patients with thrombocytopenia were higher than those in severe sepsis patients without thrombocytopenia (P=0.015 and P=0.034, respectively), and miR-130a expression was significantly lower in severe sepsis patients with thrombocytopenia (P<0.003).

CONCLUSION

Our data demonstrate that severe sepsis patients with thrombocytopenia have increased plasma and miRNA expression levels of IL-18 and decreased expression of miR-130a, suggesting that IL-18 and miR-130a might be involved in the pathophysiological process of severe sepsis with thrombocytopenia.

The role of IL-18 in type 1 diabetic nephropathy: The problem and future treatment

Diabetic vascular complication is a leading cause of diabetic nephropathy, a progressive increase in urinary albumin excretion coupled with elevated blood pressure leading to declined glomerular filtration and eventually end stage renal failure. There is growing evidence that activated inflammation is contributing factor to the pathogenesis of diabetic nephropathy. Meanwhile, IL-18, a member of the IL-1 family of inflammatory cytokines, is involved in the development and progression of diabetic nephropathy. However, the benefits derived from the current therapeutics for diabetic nephropathy strategies still provide imperfect protection against renal progression. This imperfection points to the need for newer therapeutic agents that have potential to affect primary mechanisms contributing to the pathogenesis of diabetic nephropathy. Therefore, the recognition of IL-18 as significant pathogenic mediators in diabetic nephropathy leaves open the possibility of new potential therapeutic targets.

T cell immune abnormalities in immune thrombocytopenia

Immune thrombocytopenia is an autoimmune disease with abnormal T cell immunity. Cytotoxic T cells, abnormal T regulatory cells, helper T cell imbalance, megakaryocyte maturation abnormalities and abnormal T cell anergy are involved in the pathogenesis of this condition. The loss of T cell-mediated immune tolerance to platelet auto-antigens plays a crucial role in immune thrombocytopenia. The induction of T cell tolerance is an important mechanism by which the pathogenesis and treatment of immune thrombocytopenia can be studied. Studies regarding the roles of the new inducible costimulator signal transduction pathway, the ubiquitin proteasome pathway, and the nuclear factor kappa B signal transduction pathway in the induction of T cell tolerance can help improve our understanding of immune theory and may provide a new theoretical basis for studying the pathogenesis and treatment of immune thrombocytopenia.

Effects of IFN-γ on IL-18 Expression in Pregnant Rats and Pregnancy Outcomes

The present study focused on establishing the effects of interferon-gamma (IFN-γ) on interleukin-18 (IL-18) expression patterns and pregnancy outcomes in pregnant rats. Pregnant rats at the post-implantation stage were randomized into control, low IFN-γ (L-IFN-γ) and high IFN-γ groups (H-IFN-γ) that received normal saline, 100 IU/g of IFN-γ and 500 IU/g of IFN-γ vaginal muscular injection, respectively. The effects of IFN-γ on IL-18 expression and pregnancy outcomes were assessed systematically using several methods, including immunohistochemistry streptavidin-perosidase (SP), image pattern analysis, enzyme-linked immune-sorbent assay (ELISA), whole blood count (WBC) count, microscopy and visual observation. IL-18 was detected in the uteri of all pregnant rats, and mainly distributed in the endometrium, decidual cells, vascular endothelium and myometrium. Immunohistochemistry and image pattern analyses revealed significantly lower IL-18 expression in the H-IFN-γ group compared to the L-IFN-γ and control groups (p<0.01), indicating that high doses of IFN-γ induce downregulation of IL-18 in the uterus of pregnant rats. ELISA results disclosed that IL-18 expression in peripheral blood of the H-IFN-γ group was lower than that of the L-IFN-γ group (p<0.05), and significantly reduced compared to the control group (p<0.01). Moreover, the number of peripheral leukocytes in the H-IFN-γ group was significantly higher than those in the control and L-IFN-γ groups (p<0.01). Morphology analysis showed no evident differences between the L-IFN-γ and control groups. However, for the H-IFN-γ group, uterine mucosa bleeding, necrosis and excoriation were observed using microscopy. Visual observation revealed marroon, swelling, crassitude and no embryo in the uterus, which are obvious indicators of abortion. These results indicate that IFN-γ plays a regulatory role in IL-18 expression in the uterus and peripheral blood of pregnant rats at the post-implantation stage. Moreover, high levels (500 IU/g) of IFN-γ influence normal pregnancy at the early stages in rats by downregulating IL-18 expression in the uterus and peripheral blood and increasing the number of peripheral leukocytes, consequently triggering termination of pregnancy.

The role of T cell immunoglobulin and mucin domain-3 in immune thrombocytopenia

T cell immunoglobulin and mucin domain-3 (TIM-3), originally identified as a T helper (Th) 1-specific type I membrane protein, plays a vital role in Th1 immunity and tolerance induction through interaction with its ligand, galectin-9. The binding of TIM-3 by galectin-9 serves to downregulate Th1 responses. Moreover, the regulatory function of TIM-3 has been extended to other cells, such as Th17 cells, CD4(+) CD25(+) regulatory T cells (Tregs), CD8(+) T cells and certain innate immune cells. Previous studies have acknowledged that the TIM-3 pathway is involved in the pathogenesis of several human autoimmune diseases, such as systemic lupus erythematous, rheumatoid arthritis and aplastic anaemia. Moreover, genetic data suggest a role for TIM-3 in human autoimmune diseases. However, in immune thrombocytopenia (ITP), a common Th1- and possibly Th17-biased autoimmune disorder, the role of TIM-3 has not been explored. Recently, our data have demonstrated that TIM-3 expression is reduced in ITP patients, and we have found a potential link between ITP and the TIM-3 pathway. In this article, we discuss and speculate on the role of the TIM-3 pathway in ITP.

Interleukin-18 gene promoter--607 A/C polymorphism and the risk of immune thrombocytopenia

Interleukin-18 (IL-18) is a T helper 1 cytokine, which is postulated to play a role in immune thrombocytopenia (ITP). The aim of this study was to determine whether IL-18 promoter gene -607 A/C polymorphism was associated with ITP. Three-hundred and fifty-four Chinese ITP patients and 300 Chinese healthy individuals were enrolled. Genomic DNA was extracted from the peripheral blood. Polymerase chain reaction-restriction fragment length polymorphism (RFLP) was used to genotype the DNA samples for single nucleotide polymorphism (SNP)-607. Allelic and genotypic frequencies were compared between the case-control groups by the chi-square test. The results showed that the frequencies of the CC, CA and AA genotypes and C and A allele were 32.4, 47.8, 19.8, 56.4 and 43.6% in ITP patients and 32.3, 50.4, 17.3, 57.5 and 42.5% in the controls, respectively. There was no significant difference in either genotypes or allelic distribution between ITP patients and the controls. Furthermore, stratified analysis by the platelet count, age and disease course including ITP with severe thrombocytopenia (sITP), non-sITP, acute adult, chronic adult, acute childhood and chronic childhood revealed no significant difference in genotype and alleles distribution. In conclusion, this polymorphism was almost equally distributed between ITP patients and the controls. These data showed that this SNP may not be used as a stratification marker to predict the susceptibility to Chinese ITP.

Absence of association of interleukin-18 gene polymorphisms with primary immune thrombocytopenia in a Chinese Han population

Interleukin-18 (IL-18) is an inflammatory cytokine that plays an important role in autoimmune disease by inducing interferon-γ secretion. Considering the abnormal serum concentration of IL-18 in primary immune thrombocytopenia (ITP) patients and the regulated effect of IL-18 gene polymorphisms on its production, the aim of this study was to investigate a possible association between the IL-18 promoter polymorphisms (-137 G/C and -607 C/A sites) and genetic susceptibility to ITP in a Chinese Han population. A total of 181 ITP patients and 163 healthy controls were included in this study; IL-18 gene promoter polymorphisms were analyzed by a polymerase chain reaction with sequence-specific primers. No significant differences in genotype (-607: χ(2)=0.307, p=0.858; -137: χ(2)=0.378, p=0.828) and allele frequencies (-607: χ(2)=0.004, p=0.949; -137: χ(2)=0.307, p=0.858) were found between total ITP patients and normal controls. We further analyzed the association of IL-18 polymorphisms with clinical parameters of ITP patients, including first onset age and clinical therapy response to glucocorticoids, and no difference was revealed. In conclusion, IL-18 promoter polymorphisms may not be associated with genetic susceptibility to ITP in a Chinese Han population.

Host biomarkers distinguish dengue from leptospirosis in Colombia: a case-control study

BACKGROUND

Dengue fever and leptospirosis have partially overlapping geographic distributions, similar clinical presentations and potentially life-threatening complications but require different treatments. Distinguishing between these cosmopolitan emerging pathogens represents a diagnostic dilemma of global importance. We hypothesized that perturbations in host biomarkers can differentiate between individuals with dengue fever and leptospirosis during the acute phase of illness.

METHODS

We randomly selected subjects from a prospective cohort study of acute febrile illness in Bucaramanga, Colombia and tested 19 serum biomarkers by ELISA in dengue fever (DF, n = 113) compared to subjects with leptospirosis (n = 47). Biomarkers were selected for further analysis if they had good discriminatory ability (area under the ROC curve (AUC) >0.80) and were beyond a reference range (assessed using local healthy controls).

RESULTS

Nine biomarkers differed significantly between dengue fever and leptospirosis, with higher levels of Angptl3, IL-18BP, IP-10/CXCL10, Platelet Factor 4, sICAM-1, Factor D, sEng and sKDR in dengue and higher levels of sTie-2 in leptospirosis (p < 0.001 for all comparisons). Two biomarkers, sEng and IL18BP, showed excellent discriminatory ability (AUROC >0.90). When incorporated into multivariable models, sEng and IL18BP improved the diagnostic accuracy of clinical information alone.

CONCLUSIONS

These results suggest that host biomarkers may have utility in differentiating between dengue and leptospirosis, clinically similar conditions of different etiology.

Detection of expression of IL-18 and its binding protein in Egyptian pediatric immune thrombocytopenic purpura

Immune thrombocytopenic purpura (ITP) is an autoimmune disorder, characterized by dysfunctional cellular immunity including the presence of activated platelet specific autoreactive T cells that recognize and respond to autologous platelet antigens. Autoreactive T cells drive the generation of platelet reactive autoantibodies by B cells as well as T-cytotoxic cell-mediated lysis of platelets. Interleukin-18 (IL-18) is a mediator of T helper type 1 cell responses synergistically with IL-12 that initiate and promote host defense and inflammation. IL-18 has a specific binding protein (IL-18BP) which belongs to the immunoglobulin superfamily. In the present study, serum level and messenger RNA( mRNA) expression of IL-18 as well as IL-18BP mRNA expression were measured in peripheral blood mononuclear cells (PBMNCs) of 100 Egyptian pediatric patients with ITP (70 acute and 30 chronic). In addition to this, we recruited 80 healthy volunteers in order to investigate the possible association between the imbalance of IL-18 and IL-18 BP expressions and the pathogenesis of ITP. IL-18 serum level and mRNA expression were not elevated in cases more than in the control group, but IL-18 mRNA was higher in chronic cases when compared to the acute ones (p=0.031) and there was a good negative correlation between the platelet count and serum IL-18. IL-18 BP m-RNA was slightly elevated in cases more than in the control group (95% Confidence interval=1.15-2.01). Our results were not supportive for previous findings of elevated IL18/BP mRNA ratio in ITP patients. This could be referred to the fact that autoimmune diseases are complex genetic disorders, therefore further studies on polymorphisms affecting IL-18 gene expression as well as kinetics of IL-18 expression are required to evaluate the role of interleukin 18 and its binding protein in the pathogenesis of ITP.

Effects of high-dose dexamethasone on regulating interleukin-22 production and correcting Th1 and Th22 polarization in immune thrombocytopenia

BACKGROUND

T-cell dysregulation and T-cell-related cytokine abnormalities are involved in the pathogenesis of immune thrombocytopenia (ITP). One of our previous studies showed that elevated IL-22 correlated to Th1 and Th22 cells plays an important role in the immunopathogenesis of ITP. In this study, we aimed to investigate the effects of high-dose dexamethasone(HD-DXM) on IL-22 production and on the IL-22-producing T-cell subsets in ITP patients.

METHODS

IL-22 plasma levels and the percentages of Th1, Th17, and Th22 cells were determined by enzyme-linked immunosorbent assay and flow cytometry in 25 ITP patients receiving DXM 40 mg/day for 4 consecutive days.

RESULTS

Plasma IL-22 concentrations and the percentages of Th1 and Th22 cells were significantly increased in pretherapy patients relative to controls (P<0.05), but the percentage of Th17 cells was not. HD-DXM administration reduced IL-22 production and corrected the imbalance between Th1 and Th22 subsets. IL-22 levels were positively correlated with Th1 and Th22 cells in ITP patients before and after HD-DXM treatment.

CONCLUSION

These results suggest that HD-DXM may regulate the production of IL-22 in ITP, possibly by correcting Th1 and Th22 polarization.

Imbalance of interleukin-18 and interleukin-18 binding protein in children with Henoch-Schönlein purpura

The balance between interleukin-18 (IL-18) and its endogenous antagonist, IL-18 binding protein (IL-18BP), was evaluated in children with Henoch-Schönlein purpura (HSP). Plasma IL-18 and IL-18BP levels and peripheral blood mononuclear cell IL-18 mRNA expression were significantly higher in patients with active HSP (n = 30) than in healthy controls (n = 20); IL-18BP mRNA expression was similar in active HSP and controls. Plasma levels and mRNA expression of IL-18 and IL-18BP in patients in remission (n = 19) were similar to those in controls. The ratios of IL-18 / IL-18BP plasma levels and IL-18 / IL-18BP mRNA levels in active HSP were significantly higher than in patients in remission and healthy controls. Thus, adequate IL-18BP to block the proinflammatory activity of IL-18 may not be present in active HSP and regulation of the IL-18 / IL-18BP balance might provide a potential therapeutic strategy.

Recent progress in understanding the pathogenesis of immune thrombocytopenia

PURPOSE OF REVIEW

Immune thrombocytopenia (ITP) is a bleeding disorder in which both antibody and cell-mediated autoimmune responses are directed against an individual's own platelets and/or megakaryocytes, leading to either enhanced platelet destruction and/or reduced platelet production, respectively. The cause of this platelet-specific autoimmunity remains unknown, but there has been a constant stream of recent publications that suggest ITP is the result of T-cell dysregulation.

RECENT FINDINGS

In the last 18 months, a rich tapestry of studies has emerged that seems to clarify some immunopathologic issues in ITP while raising new questions related to ITP pathogenesis. The current view on the immunopathogenic mechanisms associated with ITP appears to particularly concentrate on how incompetent CD4+ T-regulatory cells (Tregs) allow autoimmune effector mechanisms to proceed and cause thrombocytopenia. There is a parallel body of recent literature focusing on molecular mimicry mechanisms, B-cell abnormalities, abnormal cytokine patterns and genetic studies in ITP. Of interest, one can recognize inter-relationships between these immune dysregulations.

SUMMARY

This article will discuss the literature from the past 18 months pertaining to these observations and will show that whereas many of the T-cell defects have been clarified, new questions have also come to light and more immunopathological research is warranted.

High-dose dexamethasone regulates interleukin-18 and interleukin-18 binding protein in idiopathic thrombocytopenic purpura

To evaluate the effects of high-dose dexamethasone (HD-DXM) on the balance of interleukin-18 (IL-18) and its endogenous antagonist IL-18 binding protein (IL-18BP) in ITP patients, IL-18, IL-18BP as well as IFN-gamma, IL-4 plasma levels and platelet counts were determined in 17 ITP patients receiving DXM 40 mg/day for four consecutive days and in 24 healthy subjects. Using RT-PCR, the mRNA expression of IL-18, IL-18BP, IFN-gamma, IL-4, T-box (T-bet) and GATA-binding protein 3(GATA-3) were studied in all subjects. The in vitro effects of DXM on IL-18BP and IL-18 of peripheral blood mononuclear cells (PBMCs) were studied by ELISA. HD-DXM administration increased IL-18BP and reduced IL-18 expression significantly (p<0.05), which resulted in a downregulation of IL-18/IL-18BP ratio p<0.05). In vitro, DXM had a significant effect on secretion of IL-18BP while diminishing IL-18 release from cultures of PBMCs. These results suggest that downregulation of IL-18/IL-18BP might account for its clinical efficacy of HD-DXM in active ITP.