Systemic Macrophage Activation Research Articles

Macrophage-Targeted Sodium Chlorite (NP001) Slows Progression of Amyotrophic Lateral Sclerosis (ALS) through Regulation of Microbial Translocation.

Amyotrophic lateral sclerosis (ALS) is a heterogeneous, progressive, and universally fatal neurodegenerative disease. A subset of ALS patients has measurable plasma levels of lipopolysaccharide (LPS) and C-reactive protein (CRP) consistent with low-grade microbial translocation (MT). Unless interrupted, MT sets up a self-perpetuating loop of inflammation associated with systemic macrophage activation. To test whether MT contributed to ALS progression, blood specimens from a phase 2 study of NP001 in ALS patients were evaluated for changes in activity in treated patients as compared to controls over the 6-month study. In this post hoc analysis, plasma specimens from baseline and six-month timepoints were analyzed. Compared with baseline values, biomarkers related to MT were significantly decreased (LPS, LPS binding protein (LBP), IL-18, Hepatocyte growth factor (HGF), soluble CD163 (sCD163)) in NP001-treated patients as compared to controls, whereas wound healing and immunoregulatory factors were increased (IL-10, Epidermal growth factor (EGF), neopterin) by the end of study. These biomarker results linked to the positive clinical trial outcome confirm that regulation of macrophage activation may be an effective approach for the treatment of ALS and, potentially, other neuroinflammatory diseases related to MT.

Neuropathological findings in fatal COVID-19 and their associated neurological clinical manifestations

Severe cases of Coronavirus Disease 2019 (COVID-19) can present with multiple neurological symptoms. The available neuropathological studies have described different lesions; the most frequent was the presence of neuroinflammation and vascular-related lesions. The objective of this study was to report the neuropathological studies performed in a medical institution, with abundant long intensive care unit stays, and their associated clinical manifestations. This is a retrospective monocentric case series study based on the neuropathological reports of 13 autopsies with a wide range of illness duration (13–108 days). A neuroinflammatory score was calculated based on the quantification of CD8- and CD68-positive cells in representative areas of the central nervous system. This score was correlated afterwards with illness duration and parameters related to systemic inflammation. Widespread microglial and cytotoxic T-cell activation was found in all patients. There was no correlation between the neuroinflammatory score and the duration of the illness; nor with parameters of systemic inflammation such as the peak of IL-6 or the HScore (a parameter of systemic macrophage activation syndrome). Two patients had global hypoxic ischaemic damage and five patients had subacute infarcts. One patient had many more brain vascular microthrombi compared to the others and multiple subacute pituitary infarcts. SARS-CoV-2 RNA was not detected with qRT-PCR. The proportion of brain lesions in severe COVID-19 patients could be related to illness duration. In our series, with abundant long hospitalisation stays, neuroinflammation was present in all patients and was more prominent between day 34 and day 45 after onset of symptoms. Clinical correlation showed that two patients with the highest neuroinflammatory scores had severe encephalopathies that were not attributable to any other cause. The second most frequent lesions were related to vascular pathology.

Abstract 114: The Epigenetic Enzyme KMT2A/MLL1 Is A Driver Of Coronavirus Associated Coagulopathy

Objectives: Coronavirus associated coagulopathy (CAC) is postulated to be driven by systemic macrophage activation after SARS-CoV-2 infection and presents with elevated risk of thrombogenesis and hyperfibrinolysis. Previous work shows that the histone methyltransferase KMT2A/MLL1 is a key mediator of inflammatory signaling in monocytes and macrophages (Mo/Mϕs). In this study, we sought to identify the regulation of factors important in CAC by MLL1. Methods: Mice with myeloid specific knockout of MLL1 (Cre+) and littermate controls (Cre-) underwent intranasal inoculation of 2 x 10 5 pfu of the murine coronavirus MHVA59, an established model which phenocopies SARS-CoV-2 infection. Splenic Mϕs (surrogate for circulating Mo/Mϕs) were isolated and RNA and protein levels of urokinase (Plau; profibrinolytic), urokinase receptor (Plaur; profibrinolytic), and tissue factor (F3/TF; procoagulant) were analyzed using qRT-PCR and ELISA, respectively. Thromboelastography (TEG) on whole blood and urokinase activity assays from mouse plasma were performed. Urokinase and TF activity assays were performed on plasma from human samples. Results: RNA (top panel) and protein (bottom) levels of Plau, Plaur, and F3 were suppressed in the Splenic Mϕs harvested from sham (intranasal PBS) and infected Cre+ animals (white bars) compared to Splenic Mϕs harvested from Cre- animals (blue bars; Fig. 1A). Cre- mice displayed a shortened R-time (reaction time) as measured by TEG (Fig. 1B) and elevated plasma urokinase activity levels (not shown). Hospitalized COVID-positive patients (hCOV+) displayed elevated plasma urokinase and TF activity levels (Fig. 1C). Conclusions: We identify a role for MLL1 for basal expression and for coronavirus-mediated induction of factors important for fibrinolysis and coagulation in murine Mo/Mϕs and in driving coagulopathy. Our results suggest that MLL1 blockade may be an attractive strategy to combat coronavirus associated coagulopathy.

Effective therapy of tocilizumab on systemic juvenile idiopathic arthritis-associated refractory macrophage activation syndrome.

To evaluate the safety and efficacy of tocilizumab (TCZ) on refractory macrophage activation syndrome (rMAS) associated with systemic juvenile idiopathic arthritis (sJIA-rMAS). We retrospectively reviewed the charts of 14 patients diagnosed with sJIA-rMAS, who were treated with TCZ after failing conventional therapies at three hospital centres from January 2016 to December 2020. Demographic, clinical, and laboratory characteristics were recorded at the onset of MAS, before TCZ (pre-TCZ), and 14 days after TCZ (post-TCZ). The clinical manifestation of sJIA-rMAS included fever (100%), skin rashes (35.7%), lymphadenomegaly (42.9%), hepatomegaly (57.1%), splenomegaly (7.1%), gastrointestinal symptoms (28.6%), arthritis (14.3%), myalgia (28.6%), and polyserositis (14.3%). After TCZ treatment, fever (100%, 14/14), gastrointestinal symptoms (100%, 4/4), and myalgia (100%, 4/4) were significantly improved after 1 week (P < 0.05). Skin rashes, lymphadenomegaly, and arthritis also improved in many patients, but these parameters did not reach statistical significance. In post-TCZ group, decreases in levels of C-reactive protein, erythrocyte sedimentation rate, and serum ferritin of sJIA-rMAS were observed compared with pre-TCZ (P < 0.05). No disease relapse or fatality was recorded during the follow-up (25 months, range 3-60 months). TCZ is safe and effective for the treatment of sJIA-rMAS after failure of conventional therapies.

Novel biomarkers for prediction of outcome and therapeutic response in juvenile idiopathic arthritis

Introduction The search for biomarkers in juvenile idiopathic arthritis (JIA) is a promising and rapidly expanding field of investigation. The biomarkers identified so far may help to dissect the clinical heterogeneity of the illness, measure the level of disease activity, predict clinical remission, relapse, response to medications, course over time, complications, and forestall disease flares. Areas covered We provide a summary of the most recent advances in the development and application of biomarkers in JIA. We performed a PubMed search for significant articles combining predetermined keywords related to biomarkers in non-systemic and systemic JIA, chronic uveitis, and macrophage activation syndrome (MAS).The biomarkers available or under study are presented and discussed separately for non-systemic and systemic subtypes and for the two main disease complications, uveitis and MAS. Expert opinion The incorporation of valid and reliable biomarkers in standard clinical care may help to design better patient-tailored treatment regimens and to improve the therapeutic strategies based on the treat-to-target approach. The establishment of biomarkers that predict the risk of disease flare may lead to define the optimal modalities for treatment discontinuation after the achievement of clinical remission.

Bidirectional association between systemic lupus erythematosus and macrophage activation syndrome: a nationwide population-based study.

To determine the bidirectional relationship between macrophage activation syndrome (MAS) and SLE. Using the 1997-2013 Taiwan National Health Insurance Research Database, we identified patients with newly diagnosed SLE from 2001 to 2013 and selected individuals without SLE from a 1 million representative population. Propensity score (PS) matching was performed to balance incident SLE patients and individuals without SLE according to age, sex, comorbidities and medical utilization. The association between a history of MAS and SLE was studied using conditional logistic regression analysis shown as an adjusted odds ratio (aOR). The risk of MAS associated with SLE was analysed using Cox proportional regression analysis, shown as an adjusted hazard ratio (aHR), and we conducted a sensitivity analysis using various definitions of MAS. We included 10 481 SLE patients and 20 962 PS-matched (1:2) non-SLE individuals. The correlation between a history of MAS and SLE did not reach statistical significance after adjustment for potential confounders [aOR 1.18 (95% CI, 0.80, 1.75)] in the age-/sex-matched populations. In the 1:2 PS-matched populations, the risk of MAS markedly increased in patients with SLE [aHR 7.18 (95% CI 4.97, 10.36)]. Other risk factors for MAS included female gender, age ≥65 years, low income, a history of inflammatory bowel disease and a history of MAS. This nationwide, population-based study revealed that a history of MAS was not significantly associated with SLE risk. However, the risk of MAS was markedly associated with SLE and a history of MAS.

Defining the scourge of COVID-19 hyperinflammatory syndrome.

Defining the scourge of COVID-19 hyperinflammatory syndrome.

Novel paediatric presentation of COVID-19 with ARDS and cytokine storm syndrome without respiratory symptoms.

Novel paediatric presentation of COVID-19 with ARDS and cytokine storm syndrome without respiratory symptoms.

Natural Killer Cells in Systemic Autoinflammatory Diseases: A Focus on Systemic Juvenile Idiopathic Arthritis and Macrophage Activation Syndrome

Natural killer (NK) cells are innate immune lymphocytes with potent cytolytic and immune-regulatory activities. NK cells are well-known for their ability to kill infected and malignant cells in a fast and non-specific way without prior sensitization. For this purpose, NK cells are equipped with a set of cytotoxic molecules such as perforin and apoptosis-inducing proteins. NK cells also have the capacity to produce large amounts of cytokines and chemokines that synergize with their cytotoxic function and that ensure interaction with other immune cells. A less known feature of NK cells is their capacity to kill non-infected autologous cells, such as immature dendritic cells and activated T cells and monocytes. Via the release of large amounts of TNF-α and IFN-γ, NK cells may contribute to disease pathology. Conversely they may exert a regulatory role through secretion of immuno-regulatory cytokines such as GM-CSF, IL-13, and IL-10. Thus, NK cells may be important target and effector cells in the pathogenesis of autoinflammatory diseases, in particular in those disorders associated with a cytokine storm or in conditions where immune cells are highly activated. Key examples of such diseases are systemic juvenile idiopathic arthritis (sJIA) and its well-associated complication, macrophage activation syndrome (MAS). sJIA is a chronic childhood immune disorder of unknown etiology, characterized by arthritis and systemic inflammation, including a daily spiking fever and evanescent rash. MAS is a potentially fatal complication of autoimmune and autoinflammatory diseases, and most prevalently associated with sJIA. MAS is considered as a subtype of hemophagocytic lymphohistiocytosis (HLH), a systemic hyperinflammatory disorder characterized by defective cytotoxic pathways of cytotoxic T and NK cells. In this review, we describe the established features of NK cells and provide the results of a literature survey on the reported NK cell abnormalities in monogenic and multifactorial autoinflammatory disorders. Finally, we discuss the role of NK cells in the pathogenesis of sJIA and MAS.

IL-18 as a biomarker linking systemic juvenile idiopathic arthritis and macrophage activation syndrome

Systemic juvenile idiopathic arthritis (sJIA) is a childhood arthritis with features of autoinflammation and high risk of macrophage activation syndrome (MAS). IL-18 has been shown to have key roles in sJIA and MAS. We aimed to examine IL-18 levels in sJIA in relation to disease activity and history of MAS and other disease biomarkers namely S100 proteins and CXCL9. Total IL-18, CXCL9 and S100 proteins levels were determined in 40 sJIA patients, and IL-18 levels were compared between patients with regards to disease activity, history of MAS, and other biomarkers. Total IL-18 levels were significantly higher in patients with active sJIA (median 16 499 pg/ml; interquartile range (IQR) 4816-61 839), and remained persistently elevated even in the majority of patients with inactive disease (1164 pg/ml; IQR 587-3444). Patients with history of MAS had significantly higher IL-18 levels (13 380 pg/ml; IQR 4212-62 628) as compared with those without MAS history (956.5 pg/ml; IQR 276.3-4262.5). Total IL-18 performed well with area under the curve of 0.8145 and 0.84 in predicting disease activity and history of MAS, respectively. We observed moderate correlation between IL-18 and CXCL9 (R = 0.56), S100A8/A9 (R = 0.47) and S100A12 (R = 0.46). The correlation was stronger for ferritin (R = 0.74) and overall for those with active disease. Total IL-18 levels were elevated in the majority of sJIA patients regardless of clinical features, but were higher in patients with active disease and history of MAS. Change in IL-18 may reflect increased disease activity or development of MAS.

A Multiparameter Flow Cytometry Analysis Panel to Assess CD163 mRNA and Protein in Monocyte and Macrophage Populations in Hyperinflammatory Diseases.

CD163 facilitates regulation and resolution of inflammation and removal of free hemoglobin and is highly expressed in myeloid cells from patients with inflammatory disorders, such as systemic juvenile idiopathic arthritis (SJIA) and macrophage activation syndrome (MAS). Our recent studies indicate that regulation of CD163 mRNA expression is a key functional property of polarized monocytes and macrophages and is mediated at the transcriptional and posttranscriptional level, including via microRNAs. The goal of the current study is to develop a multiparameter flow cytometry panel incorporating detection of CD163 mRNA for polarized monocyte and macrophage populations in disorders such as SJIA and MAS. THP-1 cells and CD14+ human monocytes were stained using fluorochrome-conjugated Abs to myeloid surface markers, along with CD163 mRNA. Staining for mRNA could reliably detect CD163 expression while simultaneously detecting different macrophage populations using Abs targeting CD14, CD64, CD80, CD163, and CD209. This approach was found to be highly sensitive for increased mRNA expression when macrophages were polarized with IL-10 [M(IL-10)], with a strong signal over a broad range of IL-10 concentrations, and showed distinct kinetics of CD163 mRNA and protein induction upon IL-10 stimulation. Finally, this panel demonstrated clear changes in polarization markers in unstimulated monocytes from patients with SJIA and MAS, including upregulated CD163 mRNA and increased CD64 expression. This approach represents a robust and sensitive system for RNA flow cytometry, useful for studying CD163 expression as part of a multimarker panel for human monocytes and macrophages, with broad applicability to the pathogenesis of hyperinflammatory diseases.

Systemic juvenile idiopathic arthritis and macrophage activation syndrome: update on pathogenesis and treatment.

The past decade has seen substantial progress in defining the cause and pathogenesis of the chronic childhood arthropathy systemic juvenile idiopathic arthritis (SJIA) and its related complication macrophage activation syndrome (MAS). The purpose of this review is to describe and synthesize advances in this field, particularly since 2016, with the potential to transform clinical practice. Newly developed MAS classification criteria have been further studied and validated in other diseases and populations, as well as a recently proposed score to distinguish MAS from familial hemophagocytic lymphohistiocytosis. There has also been substantial progress toward understanding the genetic underpinnings of SJIA and MAS, both through targeted study of specific genes and the results of a large genome-wide association study. The immunopathogenesis of SJIA has been further elucidated through several studies regarding the proinflammatory cytokines interleukin-18, interferon (IFN)γ, and how their interplay impacts emergence of MAS. Finally, big data studies integrating genomic information with immunophenotypes have potential to provide novel insights into disease mechanisms in SJIA. Collectively, these research advances have significant implications regarding the classification and diagnosis of SJIA and MAS, and support a next generation of biologic treatments including kinase inhibitors and targeted interleukin-18 or IFNγ blockade.

021 Canakinumab use during pregnancy for the treatment of systemic onset juvenile idiopathic arthritis and refractory macrophage activation syndrome

021 Canakinumab use during pregnancy for the treatment of systemic onset juvenile idiopathic arthritis and refractory macrophage activation syndrome

Influence of Maternal Body Mass Index and Macrophage Activation on Asthma Exacerbations in Pregnancy

Obesity is a risk factor for exacerbations of asthma, but the mechanisms of this effect in pregnancy are unknown. This study determined the influence of maternal body mass index, gestational weight gain, eosinophilic inflammation, and systemic macrophage activation on the risk of exacerbations during pregnancy. Women with asthma (n= 164) participated in the study. Body mass index recorded at baseline (17 weeks gestation) was categorized as healthy weight (18.5-24.9 kg/m2), overweight (25-29.9 kg/m2), or obese (>30 kg/m2). Exacerbations requiring medical intervention were recorded prospectively. Asthma control, medication use, and fractional exhaled nitric oxide were assessed monthly; additional visits occurred during exacerbations. Peripheral blood was collected at baseline for the measurement of eosinophils, soluble CD-163, C-reactive protein, and IL-6. Exacerbations occurred in a higher proportion of overweight (51.1%) and obese (48.4%) women compared with healthy weight women (25%; P= .026). Excess weight gain during pregnancy was not associated with exacerbation risk. Macrophage activation (elevated serum soluble CD-163) was associated with exacerbations requiring oral corticosteroids (P=.043), whereas high peripheral blood eosinophils or fractional exhaled nitric oxide were not associated with exacerbation or oral corticosteroid use. Being overweight or obese confers a greater risk of asthma exacerbation during pregnancy, and may be due to systemic macrophage activation.

Low serum transferrin correlates with acute‐on‐chronic organ failure and indicates short‐term mortality in decompensated cirrhosis

Iron represents an essential, but potentially harmful micronutrient, whose regulation has been associated with poor outcome in liver disease. Its homeostasis is tightly linked to oxidative stress, bacterial infections and systemic inflammation. To study the prognostic short-term significance of iron parameters in a cohort study of patients with decompensation of cirrhosis at risk of acute-on-chronic liver failure (ACLF). Ferritin, transferrin, iron, transferrin saturation (TSAT) and hepcidin were determined in sera from 292 German patients hospitalized for decompensation of cirrhosis with ascites, of which 78 (27%) had ACLF. Short-term mortality was prospectively assessed 30 and 90days after inclusion. Transferrin concentrations were significantly lower, whereas ferritin and TSAT were higher in patients with ACLF compared to patients without ACLF (P≤.006). Transferrin, TSAT and ferritin differentially correlated with the severity of organ failure, active alcoholism and surrogates of systemic inflammation and macrophage activation. As compared with survivors, 30-day non-survivors displayed lower serum transferrin (P=.0003) and higher TSAT (P=.003), whereas 90-day non-survivors presented with higher ferritin (P=.03) and lower transferrin (P=.02). Lower transferrin (continuous or dichotomized at 87mg/dL) and consecutively higher TSAT (continuous or dichotomized >41%) indicated increased mortality within 30days and remained significant after adjustment for organ failure and inflammation in multivariate regression models and across subgroups of patients. Among the investigated indicators of iron metabolism, serum transferrin concentration was the best indicator of organ failure and an independent predictor of short-term mortality at 30days.

East Coast Fever Caused by Theileria parva Is Characterized by Macrophage Activation Associated with Vasculitis and Respiratory Failure.

Respiratory failure and death in East Coast Fever (ECF), a clinical syndrome of African cattle caused by the apicomplexan parasite Theileria parva, has historically been attributed to pulmonary infiltration by infected lymphocytes. However, immunohistochemical staining of tissue from T. parva infected cattle revealed large numbers of CD3- and CD20-negative intralesional mononuclear cells. Due to this finding, we hypothesized that macrophages play an important role in Theileria parva disease pathogenesis. Data presented here demonstrates that terminal ECF in both Holstein and Boran cattle is largely due to multisystemic histiocytic responses and resultant tissue damage. Furthermore, the combination of these histologic changes with the clinical findings, including lymphadenopathy, prolonged pyrexia, multi-lineage leukopenia, and thrombocytopenia is consistent with macrophage activation syndrome. All animals that succumbed to infection exhibited lymphohistiocytic vasculitis of small to medium caliber blood and lymphatic vessels. In pulmonary, lymphoid, splenic and hepatic tissues from Holstein cattle, the majority of intralesional macrophages were positive for CD163, and often expressed large amounts of IL-17. These data define a terminal ECF pathogenesis in which parasite-driven lymphoproliferation leads to secondary systemic macrophage activation syndrome, mononuclear vasculitis, pulmonary edema, respiratory failure and death. The accompanying macrophage phenotype defined by CD163 and IL-17 is presented in the context of this pathogenesis.

Disruption of vascular endothelial homeostasis in systemic juvenile idiopathic arthritis-associated macrophage activation syndrome: The dynamic roles of angiopoietin-1 and -2

To assess the role of angiopoietin (Ang)-1 and Ang-2 and to investigate the clinical significance of serum levels of them in systemic juvenile idiopathic arthritis (s-JIA)-associated macrophage activation syndrome (MAS), we determined these levels in 51 patients with s-JIA, 11 patients with polyarticular JIA (poly-JIA), 12 patients with virus associated hemophagocytic syndrome (VAHS), 12 patients with Kawasaki disease (KD), and 15 age-matched healthy controls (HC). The results were compared with clinical features of MAS. During the MAS phase, serum Ang-1 levels were significantly decreased compared with those during the active and inactive phases. Serum Ang-2/1 ratio were significantly elevated during the MAS phase, compared with those during the active and inactive phases. There was a rapid increase in the Ang-2/1 ratio at the onset of MAS. Serum Ang-1 and the Ang-2/1 ratio significantly correlated with measures of disease activity, including AST and LDH. Ang-2/1 dysregulation was also observed in patients with VAHS, whereas not observed in most cases of KD. The homeostasis of vascular endothelial function by Ang-1 and Ang-2 is disrupted in MAS. Serum Ang-1 levels and the Ang-2/1 ratio might represent promising indicators of disease activity for MAS.

Systemic inflammation and compromised intestinal barrier during successful treatment of HIV infection

The relationship between immunity disorders, destruction of intestinal barrier and development of systemic inflammation during antiviral therapy in patients with HIV infection is a topical issue in terms of suppression of virus replication and reduction of its role in the pathological process. Blood of HIV-infected patients given antiretroviral therapy (n = 21) and non-infected volunteers (n = 20). Identification of cells among CD4⁺ and CD8⁺ T-lymphocytes expressing markers of activation (CD38, HLA-DR), depletion (PD-1), and interleukin (IL) 7 receptor (CD127); measurement of blood levels of IL-6, neopterin, soluble CD14 (sCD14), intestinal fatty acid-binding peptide (I-FABP), and bacterial lipopolysaccharide. Correlation analysis of the dependence between cell immunity and systemic inflammation was performed. HIV-infected patients had more activated CD4⁺ and CD8⁺ T-lymphocytes and CD4⁺ T-cells expressing PD-1 marker than non-infected subjects but less CD4⁺ and CD8+ T-lymphocytes expressing CD127. Blood IL-6, neopterin, soluble CD14, I-FABP and bacterial lipopolysaccharide levels in the former were higher than in the latter HIV-infected patients showed significant correlation of cell immunity parameters with blood neopterin and FABP levels. The process of activation, depletion, and regeneration of T-lymphocytes in. HIV infection are related to the destruction of intestinal barrier and systemic macrophage activation.

Therapeutic Potential of Interferon-γ and Its Antagonists in Autoinflammation: Lessons from Murine Models of Systemic Juvenile Idiopathic Arthritis and Macrophage Activation Syndrome.

Interferon-γ (IFN-γ) affects immune responses in a complex fashion. Its immunostimulatory actions, such as macrophage activation and induction of T helper 1-type responsiveness, are widely acknowledged, however, as documented by a large body of literature, IFN-γ has also the potential to temper inflammatory processes via other pathways. In autoimmune and autoinflammatory disorders, IFN-γ can either play a disease-enforcing role or act as protective agent, depending on the nature of the disease. In animal models of any particular autoimmune disease, certain changes in the induction procedure can reverse the net outcome of introduction or ablation of IFN-γ. Here, we review the role of endogenous IFN-γ in inflammatory disorders and related murine models, with a focus on systemic juvenile idiopathic arthritis (sJIA) and macrophage activation syndrome (MAS). In particular, we discuss our recent findings in a mouse model of sJIA, in which endogenous IFN-γ acts as a regulatory agent, and compare with results from mouse models of MAS. Also, we elaborate on the complexity in the activity of IFN-γ and the resulting difficulty of predicting its value or that of its antagonists as treatment option.

Coxiella burnetii Infection With Severe Hyperferritinemia in an Asplenic Patient.

Q fever is an uncommon but likely underreported zoonotic infection. Severe hyperferritinemia has been associated with hemophagocytic lymphohistiocytosis and other infectious diseases. In this study, we report a case of Coxiella burnetii infection in an asplenic patient complicated by severe hyperferritinemia and bone marrow infiltration. In this case, the marked ferritin elevation may have been an indicator of profound systemic macrophage activation due to preferential intracellular infection of this cell type by C burnetii, perhaps exacerbated by altered mononuclear phagocyte system function in the setting of asplenia.