Hemophagocytic Lymphohistiocytosis

CD163 as a valuable diagnostic and prognostic biomarker of sepsis-associated hemophagocytic lymphohistiocytosis in critically ill children

OBJECTIVE

To investigate CD163 as an effective biomarker for identifying and predicting the outcomes of sepsis-associated hemophagocytic lymphohistiocytosis (SAHS) in children.

METHODS

We prospectively enrolled presumed sepsis patients who had developed prolonged fever (>7 days), hepatosplenomegaly, cytopenias, and hyperferritinemia (>500 ng/mL) despite antibiotic therapy. Blood samples were collected within 24 hours after enrolment. A nested case-control study was performed. The number of patients who fulfilled the HLH-2004 criteria, 28-day mortality outcomes, and 90-day mortality outcomes were recorded.

RESULTS

Sixty-nine patients were enrolled in the study. Significant increases in the levels of ferritin and soluble CD163 (sCD163) and the percentage of CD163-positive peripheral blood mononuclear cells (mCD163) and decreases in fibrinogen levels and the percentage of natural killer cells (NK %) were observed in patients with SAHS (n = 23) compared with those of patients with sepsis (n = 46). The area under the ROC curve (AUC) for ferritin combined with sCD163 was superior to the AUC for either ferritin or sCD163 for distinguishing SAHS from sepsis. Moreover, sCD163 was a prognostic factor for 28-day mortality (0.857 [0.659-1.000]).

CONCLUSIONS

sCD163 is a valuable biomarker for the differential diagnosis of SAHS from sepsis and effectively predicts 28-day mortality in children with SAHS.

Flow Cytometry for Diagnosis of Primary Immune Deficiencies-A Tertiary Center Experience From North India

Flow cytometry has emerged as a useful technology that has facilitated our understanding of the human immune system. Primary immune deficiency disorders (PIDDs) are a heterogeneous group of inherited disorders affecting the immune system. More than 350 genes causing various PIDDs have been identified. While the initial suspicion and recognition of PIDDs is clinical, laboratory tools such as flow cytometry and genetic sequencing are essential for confirmation and categorization. Genetic sequencing, however, are prohibitively expensive and not readily available in resource constrained settings. Flow cytometry remains a simple, yet powerful, tool for multi-parametric analysis of cells. While it is confirmatory of diagnosis in certain conditions, in others it helps in narrowing the list of putative genes to be analyzed. The utility of flow cytometry in diagnosis of PIDDs can be divided into four major categories: (a) Enumeration of lymphocyte subsets in peripheral blood. (b) Detection of intracellular signaling molecules, transcription factors, and cytokines. (c) Functional assessment of adaptive and innate immune cells (e.g., T cell function in severe combined immune deficiency and natural killer cell function in familial hemophagocytic lymphohistiocytosis). (d) Evaluation of normal biological processes (e.g., class switching in B cells by B cell immunophenotyping). This review focuses on use of flow cytometry in disease-specific diagnosis of PIDDs in the context of a developing country.

Sorafenib attenuated the function of natural killer cells infiltrated in HCC through inhibiting ERK1/2

Sorafenib has been systemically utilized to therapy the advanced hepatocellular carcinoma (HCC). Natural killer cells (NKs) are important cytotoxic innate lymphocytes, which can exert effector functions especially in liver and tumor. However, how Sorafenib affects the function of NKs remains to be elucidated. Here, we utilized the subcutaneous and in situ tumor bearing mice with mouse hepatoma cell line hepa 1-6. At the endpoint, the number and function of NKs in blood, liver, TDLN, and tumor were explored using FACS, ELISA, WB, etc. To confirm the direct effects of Sorafenib on NKs, the NKs were sorted using FACS, which were then stimulated with Sorafenib to detect the functions and the relevant mechanisms using qPCR, western blot, and FACS in vitro. Finally, we found that Sorafenib led to a significant block of tumor progression, but reduced the number of NK cells through suppressing the proliferation of NK cells. This phenotype made us study the terminal function of NK cells, revealing that Sorafenib could decrease the production of effector molecules and cytokines, such as perforin, granzyme B, TNF-α, IFN-γ, etc. Besides, p-ERK1/2 in NK cells was inhibited after treatment with Sorafenib, and a similar tendency of NK cells could be achieved using ERK1/2 inhibitor. Collectively, our data suggested that Sorafenib functioned as a critical inhibitor that controlled the number and function of NK cells through inhibiting ERK1/2.

Genetic characterization of pediatric primary hemophagocytic lymphohistiocytosis in China: a single-center study

To study the genetic characteristics of primary hemophagocytic lymphohistiocytosis (pHLH) in China, we investigated the genetic data and clinical features of Chinese HLH patients. We retrospectively reviewed the genetic and clinical data of patients with HLH from November 2015 to June 2018. As a result, 26 patients were diagnosed with pHLH. The median age at diagnosis was 2.8 years (range 0.1-13.7 years). The probable overall survival at 12 and 24 months was 87.6% and 62.6%, respectively. Mutations in PRF1 (38.4%) and UNC13D (26.9%) were the most common genetic abnormalities. Furthermore, we identified 19 novel mutations that had not been previously reported and were predicted to likely be pathogenic. In addition to HLH-associated genes, there were 27 other genes identified. Genotype-phenotype analysis showed that patients with disruptive mutations were significantly younger at diagnosis than those with other mutation types (2.9 years vs. 6.4 years, P = 0.036). Familial HLH patients were more prone to central nervous system involvement and seizures compared with other patients (83.3% vs. 37.5%, P = 0.019; 55.6% vs. 12.5%, P = 0.04, respectively). In summary, numerous new mutations in HLH-related genes and other genes were identified in Chinese children with pHLH. Significantly, disruptive mutation types were more likely to be found in younger patients, and familial HLH patients tended to exhibit central nervous system involvement and seizures.

Chronic TLR7 and TLR9 signaling drives anemia via differentiation of specialized hemophagocytes

Cytopenias are an important clinical problem associated with inflammatory disease and infection. We show that specialized phagocytes that internalize red blood cells develop in Toll-like receptor 7 (TLR7)-driven inflammation. TLR7 signaling caused the development of inflammatory hemophagocytes (iHPCs), which resemble splenic red pulp macrophages but are a distinct population derived from Ly6C^hi monocytes. iHPCs were responsible for anemia and thrombocytopenia in TLR7-overexpressing mice, which have a macrophage activation syndrome (MAS)-like disease. Interferon regulatory factor 5 (IRF5), associated with MAS, participated in TLR7-driven iHPC differentiation. We also found iHPCs during experimental malarial anemia, in which they required endosomal TLR and MyD88 signaling for differentiation. Our findings uncover a mechanism by which TLR7 and TLR9 specify monocyte fate and identify a specialized population of phagocytes responsible for anemia and thrombocytopenia associated with inflammation and infection.

NK cells switch from granzyme B to death receptor-mediated cytotoxicity during serial killing

Natural killer cells can kill infected and transformed cells via two different cell death mechanisms. Prager et al. show that NK cells quickly kill their first targets by releasing cytotoxic granules and only use the slower death receptor–mediated cytotoxicity for their final kill.

NK cells eliminate virus-infected and tumor cells by releasing cytotoxic granules containing granzyme B (GrzB) or by engaging death receptors that initiate caspase cascades. The orchestrated interplay between both cell death pathways remains poorly defined. Here we simultaneously measure the activities of GrzB and caspase-8 in tumor cells upon contact with human NK cells. We observed that NK cells switch from inducing a fast GrzB-mediated cell death in their first killing events to a slow death receptor–mediated killing during subsequent tumor cell encounters. Target cell contact reduced intracellular GrzB and perforin and increased surface-CD95L in NK cells over time, showing how the switch in cytotoxicity pathways is controlled. Without perforin, NK cells were unable to perform GrzB-mediated serial killing and only killed once via death receptors. In contrast, the absence of CD95 on tumor targets did not impair GrzB-mediated serial killing. This demonstrates that GrzB and death receptor–mediated cytotoxicity are differentially regulated during NK cell serial killing.

Secondary hemophagocytic lymphohistiocytosis in pediatric patients: a single center experience and factors that influenced patient prognosis

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening syndrome of excessive immune activation. Secondary HLH syndrome develops as a complication of infection, drugs, rheumatologic conditions, or malignancy. The main objectives of this work were to identify the etiology of secondary HLH and prognostic factors associated with mortality. Patients diagnosed with secondary HLH, between January 2011 and December 2016, were retrospectively included in this study. We analyzed clinical and laboratory findings as well as prognostic factors from 24 pediatric patients diagnosed with secondary HLH. The mean age of patients at the time of diagnosis was 79.9 ± 68.7 months (range: 2-202) and 54.2% of the patients were male. The most frequent HLH-2004 criterion was fever (100%). Underlying triggers of HLH were as follows: 13 (54.1%) infections, juvenile idiopathic arthritis in 5 patients (20.8%), drugs in 3 patients (12.5%), malignancies in 2 (0.8%), Kawasaki disease in 1 (0.4%) patient, and 1 (0.4%) with unknown triggers. The median time of diagnosis was 3 days (1-67 days). Overall, the mortality rate was 20.8%. In our logistic regression model, factors associated with mortality were decreased albumin levels (OR1 = 2.3[1.48-3.43]) and etoposide usage (OR2 = 1.22 [1.14-1.89]). The patient's 30-day survival was inferior among patients whose albumin level was 2 g/dL or less compared to those over 2 g/dL. Increased awareness of the underlying condition is critical in HLH patients. Our study emphasizes the prognostic significance of albumin level.

Haemophagocytic lymphohistiocytosis complicating pembrolizumab treatment for metastatic breast cancer in a patient with the PRF1A91V gene polymorphism

BACKGROUND

Immune checkpoint inhibitor therapy is a modern breakthrough in medical oncology, but it can precipitate inflammatory and autoimmune adverse effects. Among the most serious of these toxicities is haemophagocytic lymphohistiocytosis (HLH), a life-threatening disorder of unbridled immune activation that results in injury to multiple organ systems.

OBJECTIVE

Description of a case of pembrolizumab-associated HLH in a patient with a proposed underlying genetic risk factor for its occurrence.

METHODS AND RESULTS

We describe a patient with aggressive metastatic breast cancer who developed HLH while undergoing experimental treatment with pembrolizumab, resulting in critical illness and multiorgan system failure. Pembrolizumab discontinuation and high-dose corticosteroids were effective in managing HLH. Subsequent next-generation sequencing of 15 genes associated with HLH revealed a germline polymorphism in perforin-1 (PRF1), PRFA91V, that may have predisposed the patient to develop HLH. The patient has had no evidence of malignancy for 2 years following recovery despite receiving no further cancer-directed treatment.

CONCLUSIONS

HLH is a rare but serious complication of immune checkpoint blockade. Patients with underlying hypomorphic alleles in PRF1 may be predisposed to develop this toxicity. Further studies are necessary to confirm a possible link between perforin gene mutations and immune checkpoint blockade-associated HLH.

Hemophagocytic lymphohistiocytosis presenting with annular erythema multiforme-like eruptions in a patient with angioimmunoblastic T cell lymphoma: A case report

Angioimmunoblastic T cell lymphoma (AITL)-associated hemophagocytic lymphohistiocytosis (HLH) rarely occurs with annular erythema multiforme-like rashes. The present case report describes a patient who was misdiagnosed with erythema multiforme at an early stage of the disease due to annular erythema multiforme-like eruptions. However, antihistamine treatment was ineffective. The patient progressed rapidly with high fever, hepatosplenomegaly and pharyngitis. The number of copies of Epstein-Barr virus DNA continuously increased. Accompanied by the swelling of lymph nodes, the blood cell count decreased. Further bone-marrow examination and biopsy of the lymph nodes were conducted. The patient was eventually diagnosed with AITL-associated HLH, and treated with etoposide together with cyclophosphamide, doxorubicin, vincristine and prednisolone. The patient was successfully treated with several courses of chemotherapy. In view of the fact that AITL-associated HLH with annular erythema multiforme-like rashes is relatively rare worldwide and is associated with a high mortality rate, the data on previous cases were reviewed with the hope of providing clinical bases for early diagnosis and treatment of AITL-associated HLH.