CD14(dim)/CD16(bright) monocytes in hemophagocytic lymphohistiocytosis

Increased Serum Levels of sCD14 and sCD163 Indicate a Preponderant Role for Monocytes in COVID-19 Immunopathology

Background

Emerging evidence indicates a potential role for monocytes in COVID-19 immunopathology. We investigated two soluble markers of monocyte activation, sCD14 and sCD163, in COVID-19 patients, with the aim of characterizing their potential role in monocyte-macrophage disease immunopathology. To the best of our knowledge, this is the first study of its kind.

Methods

Fifty-nine SARS-Cov-2 positive hospitalized patients, classified according to ICU or non-ICU admission requirement, were prospectively recruited and analyzed by ELISA for levels of sCD14 and sCD163, along with other laboratory parameters, and compared to a healthy control group.

Results

sCD14 and sCD163 levels were significantly higher among COVID-19 patients, independently of ICU admission requirement, compared to the control group. We found a significant correlation between sCD14 levels and other inflammatory markers, particularly Interleukin-6, in the non-ICU patients group. sCD163 showed a moderate positive correlation with the time lapsed from admission to sampling, independently of severity group. Treatment with corticoids showed an interference with sCD14 levels, whereas hydroxychloroquine and tocilizumab did not.

Conclusions

Monocyte-macrophage activation markers are increased and correlate with other inflammatory markers in SARS-Cov-2 infection, in association to hospital admission. These data suggest a preponderant role for monocyte-macrophage activation in the development of immunopathology of COVID-19 patients.

Pattern of human monocyte subpopulations in health and disease

Monocytes are important cells of the innate system. They are a heterogeneous type of cells consisting of phenotypically and functionally distinct subpopulations, which play a specific role in the control, development and escalation of the immunological processes. Based on the expression of superficial CD14 and CD16 in flow cytometry, they can be divided into three subsets: classical, intermediate and non-classical. Variation in the levels of human monocyte subsets in the blood can be observed in patients in numerous pathological states, such as infections, cardiovascular and inflammatory diseases, cancer and autoimmune diseases. The aim of this review is to summarize current knowledge of human monocyte subsets and their significance in homeostasis and in pathological conditions.

Malignancy-associated hemophagocytic lymphohistiocytosis in adults: Relation to hemophagocytosis, characteristics, and outcomes

BACKGROUND

Malignancy-associated hemophagocytic lymphohistiocytosis (HLH) in adults is a highly lethal disorder. Knowledge gaps have resulted in under diagnosis or delayed diagnosis.

METHODS

The University of Texas MD Anderson Cancer Center pathology database (1991-2014) was retrospectively interrogated for the keywords "hemophagocytosis" and/or "lymphohistiocytosis." Seventy-seven adult patients were identified. All had an underlying malignancy. Sixteen patients who had insufficient documentation were excluded.

RESULTS

The majority of patients who had pathologic evidence of hemophagocytosis/lymphohistiocytosis had an incomplete workup to confirm or refute HLH using the 2004 HLH criteria (HLH-2004; n = 8 variables), which is a common problem in adult HLH. Only 13 of 61 patients (21%) met the HLH-2004 diagnostic criteria based on available retrospective data. To identify potentially missed cases of HLH, the published literature was reviewed, and selected additional variables known to be associated with adult HLH were selected, resulting in extended diagnostic criteria of 18 variables. Thirty-five patients met the extended criteria, and 33 had follow-up data available. The median overall survival of the 13 patients who met both the extended criteria and the HLH-2004 criteria was similar to that of the 20 patients who met the extended criteria but NOT the HLH-2004 criteria (1.43 vs 1.76 months, respectively; P = .34) indicating a similar underlying, aggressive, systemic process. Twenty-six patients did not meet either criteria, and 17 had follow-up data available. The median overall survival of the 17 patients who had pathologic hemophagocytosis or lymphohistiocytosis but met neither criteria was significantly superior to the survival of those who met both the extended criteria and the HLH-2004 criteria and those who met the extended criteria but not the HLH-2004 criteria (17.27 vs 1.43 vs 1.76, respectively; P = .002).

CONCLUSIONS

The addition of diagnostic laboratory variables that are more easily and rapidly available in smaller institutions and primary care settings than the HLH-2004 variables may be a good surrogate to raise early suspicion of malignancy-associated HLH. Prospective validation is warranted. Cancer 2016. © 2016 American Cancer Society. Cancer 2016;122:2857-2866. © 2016 American Cancer Society.

Interactions of monocyte subpopulations generated from cord blood CD34(+) hematopoietic progenitors with tumor cells: assessment of antitumor potential

Monocytes and their subsets (CD14(++)CD16(+) and CD14(+)CD16(-)) generated from cord blood CD34(+) progenitor cells were used for determination of their capacity to interact with tumor cells in vitro and in vivo. The studies in vitro included adhesion to human umbilical vein endothelial cells, cytotoxicity, production of toxic mediators: reactive oxygen and nitrogen intermediates (ROI and RNI, respectively), and finally their effect on transplantable human tumor growth in nonobese diabetic severe combined immunodeficient mice. The CD14(++)CD16(+) subset exhibited an increased adherence to human umbilical vein endothelial cells and cytotoxicity toward tumor cells in vitro. CD14(+)CD16(-) monocytes showed a higher production of reactive oxygen and nitrogen intermediates after stimulation with tumor cells, and more pronounced inhibition of tumor growth in vivo. The results revealed significant differences in the behavior of CD14(++)CD16(+) and CD14(+)CD16(-) monocyte subsets toward tumor cells, thus providing further evidence that CD34(+) cell-derived monocytes differ in this respect from blood monocytes. The protocol for generation of monocytes with antitumor reactivity described here may be useful to obtain monocytes from CD34(+) progenitor cells of cancer patients. This might offer a basis for a novel approach for various forms of cellular immunotherapy of cancer.

Alternative activation in systemic juvenile idiopathic arthritis monocytes

Systemic juvenile idiopathic arthritis (SJIA) is a chronic autoinflammatory condition. The association with macrophage activation syndrome, and the therapeutic efficacy of inhibiting monocyte-derived cytokines, has implicated these cells in SJIA pathogenesis. To characterize the activation state (classical/M1 vs. alternative/M2) of SJIA monocytes, we immunophenotyped monocytes using several approaches. Monocyte transcripts were analyzed by microarray and quantitative PCR. Surface proteins were measured at the single cell level using flow cytometry. Cytokine production was evaluated by intracellular staining and ELISA. CD14(++)CD16(-) and CD14(+)CD16(+) monocyte subsets are activated in SJIA. A mixed M1/M2 activation phenotype is apparent at the single cell level, especially during flare. Consistent with an M2 phenotype, SJIA monocytes produce IL-1β after LPS exposure, but do not secrete it. Despite the inflammatory nature of active SJIA, circulating monocytes demonstrate significant anti-inflammatory features. The persistence of some of these phenotypes during clinically inactive disease argues that this state reflects compensated inflammation.

Disruption of MyD88 signaling suppresses hemophagocytic lymphohistiocytosis in mice

Hemophagocytic lymphohistiocytosis (HLH) is a rare inflammatory disorder with a poor prognosis for affected individuals. To find a means of suppressing the clinical phenotype, we investigated the cellular and molecular mechanisms leading to HLH in Unc13d(jinx/jinx) mice, in which cytolytic function of NK and CD8(+) T cells is impaired. Unc13d(jinx/jinx) mutants infected with lymphochoriomeningitis virus (LCMV) present typical clinical features of HLH, including splenomegaly, elevated serum IFNγ, and anemia. Proteins mediating cell-cell contact, cytokine signaling or Toll-like receptor (TLR) signaling were analyzed. We show that neither the integrin CD18, which is involved in adhesion between antigen-presenting cells and effector T cells, nor tumor necrosis factor (TNF) made nonredundant contributions to the disease phenotype. Disruption of IFNγ signaling reduced immune cell activation in Unc13d(jinx/jinx) mice, but also resulted in uncontrolled viral proliferation and exaggerated release of inflammatory cytokines. Abrogating the function of myeloid differentiation primary response gene 88 (MyD88) in Unc13d(jinx/jinx) mice suppressed immune cell activation and controlled cytokine production in an IL-1 receptor 1 (IL-1R1)-independent way. Our findings implicate MyD88 as the key initiator of myeloid and lymphoid proliferation in HLH, and suggest that blockade of this signaling molecule may reduce immunopathology in patients.

The response to TLR ligation of human CD16⁺CD14⁻ monocytes is weakly modulated as a consequence of persistent infection with the hepatitis C virus

Little is known about the frequency and function of CD16(+)CD14(-) monocytes from chronic HCV patients. We observed that the absolute numbers and ratio of CD16(+)CD14(-) to CD14(+)CD16(-) monocytes were similar between chronic HCV patients and healthy individuals. Functionally, we found that CD16(+)CD14(-) monocytes are more responsive to TLR8-ligation and only weakly responsive to LPS stimulation in producing TNF as compared to CD14(+)CD16(-) monocytes. We found no overt impairment of the function of CD16(+)CD14(-) monocytes from patients, except for an augmented induction of MIP-1β-producing CD16(+)CD14(-) monocytes upon TLR4-ligation. However, the increased frequency of MIP-1β-producing CD16(+)CD14(-) monocytes was not associated with viral load, ALT or fibrosis level. Our findings indicate that, different from other infectious diseases, the frequency and function of CD16(+)CD14(-) monocytes are only minimally altered as a consequence of the persistent state of HCV infections, and our findings therefore do not suggest a role for CD16(+)CD14(-) monocytes in HCV pathogenesis.

Preparations of intravenous immunoglobulins diminish the number and proinflammatory response of CD14+CD16++ monocytes in common variable immunodeficiency (CVID) patients

We have studied the effect of intravenous immunoglobulins (IVIG) on monocyte subpopulations and cytokine production in patients with CVID. The absolute number of CD14(+)CD16(++) monocytes decreased on average 2.5-fold 4h after IVIG and after 20h returned to the baseline. The cytokine level in the supernatants of peripheral blood mononuclear cells (PBMC) after ex vivo LPS stimulation demonstrated the >2-fold decrease in TNF production 4h after IVIG. The TNF expression, which is higher in the CD14(+)CD16(++) monocytes, was decreased in these cells by IVIG in 4/7 CVID cases. In vitro exposure of the healthy individuals' monocytes to the IVIG preparation resulted in reduced TNF production, which was overcome by blockade of the FcγRIIB in the CD14(+)CD16(++) CD32B(high) monocytes. Our data suggest that reduction in the number of CD14(+)CD16(++) monocytes and the blockade of their cytokine production via triggering CD32B can contribute to the anti-inflammatory action of IVIG.

Standardized single-platform assay for human monocyte subpopulations: Lower CD14+CD16++ monocytes in females

We present a novel single-platform assay for determination of the absolute number of human blood monocyte subpopulations, i.e., the CD14(++)CD16(-) and the CD14(+)CD16(++) monocytes. A four-color combination of antibodies to CD14, CD16, CD45, and HLA-DR reduces the spill-over of natural killer cells and of granulocytes into the CD14(+)CD16(++) monocyte gate. For these CD14(+)CD16(++) monocytes, the intra-assay coefficient of variation (CV) was 4.1% and the inter-assay CV was 8.5%. Looking at a cohort of 40 donors aged 18-60 years, we found no age dependence. There was however an effect of gender in that females had lower CD14(+)CD16(++) monocytes (45.4 +/- 13.5 cells/microl) compared with males (59.1 +/- 20.3 cells/microl) (P < 0.02). Using this novel approach, we can confirm that exercise will lead to more than three-fold increase of the CD14(+)CD16(++) monocytes. Also, we show that therapy with low doses of glucocorticoids will deplete these cells. This robust single-platform assay may be a useful tool for monitoring the absolute number of monocyte subpopulations in health and disease.

Haemophagocytic syndrome and rickettsial diseases

Haemophagocytic lymphohistiocytosis is a rare but potentially fatal disease resulting from dysregulated activation and proliferation of lymphocytes. We present a case of haemophagocytic syndrome occurring in a 5-year-old Italian boy as a complication of Mediterranean spotted fever. The characteristics of this case have been analysed and contextualized among those of another 15 cases of haemophagocytic syndrome associated with rickettsial diseases found through a systematic review of the international literature.

Pediatric Bone Marrow Interpretation

The evaluation of pediatric bone marrow poses specific challenges when compared with the general adult population. These challenges stem in part from the higher likelihood of congenital disorders with hematopoietic manifestations, some of which may give rise to hematologic malignancies. Familiarity with the spectrum of disorders seen in the pediatric age group allows for an appropriate and focused differential diagnosis. This review addresses the diagnostic workup of pediatric bone marrow samples, as directed by the peripheral blood and bone marrow findings in the context of the patient's clinical history. Recommendations for the appropriate use of ancillary studies in various scenarios are provided.

Viral infections associated with haemophagocytic syndrome

Haemophagocytic syndrome (HPS) or haemophagocytic lymphohistiocytosis (HLH) is a rare disease caused by a dysfunction of cytotoxic T cells and NK cells. This T cell/NK cell dysregulation causes an aberrant cytokine release, resulting in proliferation/activation of histiocytes with subsequent haemophagocytosis. Histiocytic infiltration of the reticuloendothelial system results in hepatomegaly, splenomegaly, lymphadenopathy and pancytopenia ultimately leading to multiple organ dysfunctions. Common clinical features include high fevers despite broad spectrum antimicrobials, maculopapular rash, neurological symptoms, coagulopathy and abnormal liver function tests. Haemophagocytic syndrome can be either primary, i.e. due to an underlying genetic defect or secondary, associated with malignancies, autoimmune diseases (also called macrophage activation syndrome) or infections. Infectious triggers are most commonly due to viral infections mainly of the herpes group, with EBV being the most common cause. HPS can be fatal if untreated. Early recognition of the clinical presentation and laboratory abnormalities associated with HPS and prompt initiation of treatment can be life saving. HPS triggered by viral infections generally does not respond to specific antiviral therapy but may be treated with immunosuppressive/immunomodulatory agents and, in refractory cases, with bone marrow transplantation. Copyright © 2010 John Wiley & Sons, Ltd.

The successful treatment of haemophagocytic syndrome in patients with human immunodeficiency virus-associated multi-centric Castleman's disease

Both virus-associated haemophagocytic syndrome (HPS) and human immunodeficiency virus-associated multi-centric Castleman's disease (HIV-MCD) induced by human herpesvirus-8 (HHV-8) are extremely rare. We therefore wished to investigate their occurrence together, and establish the degree of cytokine activation present. From a prospective cohort of individuals with HIV-MCD, we investigated the incidence and outcomes of HPS and measured 15 inflammatory cytokines and the plasma HHV-8 viral loads before and during follow-up. Of 44 patients with HIV-MCD with an incidence of 4.3/10,000 patient years, four individuals (9%) were diagnosed with HPS. All are in remission (range 6-28 months) following splenectomy, etoposide and rituximab-based therapy. Plasma HHV-8 levels were raised markedly at presentation (median 3,840,000 copies/ml). Histological samples from spleen, splenic hilar lymph nodes and bone marrow demonstrated increased phagocytosis by histiocytes and presence of HHV-8-infected plasmablasts outside the follicles. Surprisingly, many known inflammatory plasma cytokines were not elevated, although interleukin (IL)-8 and interferon-gamma were increased in all cases and IL-6 levels were raised in three of four patients. HPS in the setting of HIV-MCD is common and treatment can be successful provided the diagnosis is made appropriately. Systemic activation of cytokines was limited, suggesting that immunosuppressive therapy with steroids is not indicated in HHV-8-driven HPS.

Infections associated with haemophagocytic syndrome

Haemophagocytic syndrome or haemophagocytic lymphohistiocytosis is a rare disease that is often fatal despite treatment. Haemophagocytic syndrome is caused by a dysregulation in natural killer T-cell function, resulting in activation and proliferation of lymphocytes or histiocytes with uncontrolled haemophagocytosis and cytokine overproduction. The syndrome is characterised by fever, hepatosplenomegaly, cytopenias, liver dysfunction, and hyperferritinaemia. Haemophagocytic syndrome can be either primary, with a genetic aetiology, or secondary, associated with malignancies, autoimmune diseases, or infections. Infections associated with haemophagocytic syndrome are most frequently caused by viruses, particularly Epstein-Barr virus (EBV). We present a case of EBV-associated haemophagocytic syndrome in a young adult with no known immunosuppression. We briefly review haemophagocytic syndrome and then discuss its associated infections, particularly EBV and other herpes viruses, HIV, influenza, parvovirus, and hepatitis viruses, as well as bacterial, fungal, and parasitic organisms.

Selective expansion of the CD14(+)/CD16(bright) subpopulation of circulating monocytes in patients with hemophagocytic syndrome

Overproduction of proinflammatory cytokines is characteristic of hemophagocytic syndrome (HPS), a highly lethal inflammatory disease. Peripheral blood monocytes include two distinct subpopulations according to surface antigen expression: a major type, CD14(+)/CD16(-) (classical monocytes), and a minor type, CD14(+)/CD16(bright) (proinflammatory monocytes). Among peripheral blood monocytes from HPS patients, CD14(+)/CD16(bright) cells were increased, together with lipopolysaccharide-induced production of tumor necrosis factor (TNF)-alpha and interleukin (IL)-6. By three-color immunofluorescence, CD14(+)/CD16(bright) monocytes exhibited more intense human leukocytic antigen DR than CD14(+)/CD16(-) monocytes, consistent with greater maturity. Serum IL-6, TNF-alpha, and IL-8 were increased in HPS patients. A sensitive inflammatory marker, neutrophil CD64 expression, also was significantly elevated in HPS patients. In conclusion, expansion of proinflammatory monocytes and increased expression of neutrophil CD64 appeared to be important in the pathophysiology of HPS. Expansion of CD14(+)/CD16(bright) monocytes and neutrophil CD64 expression could serve as indicators of the inflammatory state in HPS.

The CD14+ CD16+ blood monocytes: their role in infection and inflammation

Blood monocyte subpopulations have been defined in man initially, and the two major types of monocytes are the CD14++ CD16- and the CD14+ CD16+ monocytes. These cells have been shown to exhibit distinct phenotype and function, and the CD14+ CD16+ were labeled proinflammatory based on higher expression of proinflammatory cytokines and higher potency in antigen presentation. The current review describes these properties, including the relationship to dendritic cells, and summarizes the host of publications about CD14+ CD16+ monocytes in inflammation and infectious disease in man, all of which suggest a crucial role of these cells in the disease processes. The review also covers the more recent description of homologues of these cells in other model species, which is expected to better define the role of monocyte subsets in disease.

Persistent abnormalities in peripheral blood dendritic cells and monocytes from HIV-1-positive patients after 1 year of antiretroviral therapy

Antiretroviral therapy (ART) has led to marked decreases in morbidity and mortality rates among HIV-1-positive patients; however, immune recovery is not complete. Although dendritic cells (DCs) were shown to be involved in HIV-1 pathogenesis, few studies have investigated the effect of ART on DCs. We have analyzed the effect of ART on numerical distribution, expression of chemokine receptors, and ex vivo production of inflammatory cytokines by peripheral blood (PB) monocytes and DCs in a cohort of chronically infected HIV-1-positive patients. Patients were tested before therapy and at weeks +2, +4, +8, +12, and +52 after starting ART.Our results show an incomplete T-cell immune reconstitution in chronically infected patients who had undetectable plasma viremia while taking ART for 1 year. This was associated with persistent abnormalities at week +52 of ART, corresponding to increased numbers of CD16 DCs and monocytes, as well as altered expression of CXC chemokine receptors, in the form of increased CXCR1 expression on monocytes and decreased reactivity for CXCR2 and/or CXCR4 on myeloid and plasmacytoid DCs. In addition, an abnormally high spontaneous ex vivo secretion of inflammatory cytokines by CD16 DCs and monocytes was still detected after 1 year of ART. These abnormalities were especially pronounced in patients with less than 200 CD4 T cells/microL, which could be related to the persistence of undetected viral replication and sustained immune activation.

Subtyping of natural killer cell cytotoxicity deficiencies in haemophagocytic lymphohistocytosis provides therapeutic guidance

The familial form of haemophagocytic lymphohistiocytosis (HLH) is a fatal disease, with allogeneic stem cell transplantation (SCT) being the only curative treatment. In contrast, patients with secondary (infection-associated) HLH usually do not require SCT. Since it often is difficult to distinguish primary and secondary HLH, we wanted to identify a tool that provides guidance on whether SCT is required. The clinical outcome of 65 HLH patients was analysed in relation to the recently reported four types of defects in natural killer (NK)-cell cytotoxicity in HLH. None (0%) of the 36 patients with NK-cell deficiency type 3 attained a sustained (1-year) remission after stopping therapy without receiving SCT, in contrast to 45% (13/29) non-type 3 patients (P < 0.001). Most type 3 patients (22/36) underwent SCT (14/22, 64% are alive), whereas 11 of 14 that did not receive SCT died, and the three others had received HLH-therapy during the last year of follow-up. Of 54 patients analysed for perforin expression and/or mutation, the five with perforin deficiency were all type 3 patients. The data suggests that HLH patients with NK-cell deficiency type 3 will probably require SCT to survive. Thus, NK-cell deficiency classification may provide valuable guidance in judging whether an HLH-patient needs SCT.