Analysis of Familial Hemophagocytic Lymphohistiocytosis Type 4 (FHL-4) Mutant Proteins Reveals that S-Acylation Is Required for the Function of Syntaxin 11 in Natural Killer Cells

Context.— Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening disorder of immune regulation that can eventually result in end-organ damage and death. HLH is characterized by uncontrolled activation of cytotoxic T lymphocytes, natural killer cells, and macrophages that can lead to a cytokine storm. The diagnosis of HLH is often challenging due to the diverse clinical manifestations and the presence of several diagnostic mimics. The prognosis is generally poor, warranting rapid diagnosis and aggressive management. Objective.— To provide a comprehensive review of the pathogenesis, clinical features, diagnosis, and management of HLH. Data Sources.— Peer-reviewed literature. Conclusions.— HLH is a condition where a complete understanding of the pathogenesis, early diagnosis, and proper management has an important role in determining patient outcome. Genetic mutations causing impairment in the function of cytotoxic T lymphocytes and natural killer cells have been identified as the root cause of familial HLH; however, the specific pathogenesis of acquired HLH is unclear. The HLH-2004 protocol used in the diagnosis of HLH was originally developed for the pediatric population. The HLH-2004 protocol still forms the basis of the diagnosis of HLH in adults, although its use in adults has not been formally validated yet. Treatment of HLH is primarily based on the HLH-94 protocol, which involves suppressing the inflammatory response, but the treatment needs to be modified in adults depending on the underlying cause and comorbidities.

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Flow cytometry in the diagnosis of hemophagocytic lymphohistiocytosis

Orvosi Hetilap ◽

10.1556/oh.2014.29790 ◽

2014 ◽

Vol 155 (10) ◽

pp. 389-395

Author(s):

Éva Pállinger ◽

Dániel Erdélyi ◽

Gábor Kovács ◽

Gergely Kriván ◽

Zsuzsanna Korponay ◽

...

Keyword(s):

Flow Cytometry ◽

Case Report ◽

Natural Killer Cells ◽

Natural Killer ◽

Hemophagocytic Lymphohistiocytosis ◽

Killer Cell ◽

Interleukin 2 ◽

Cell Surface Expression ◽

Cytotoxic T Cell ◽

Killer Cells

Hemophagocytic lymphohistiocytosis is a multisystem inflammation, generated by the uncontrolled and excessive activation of cytotoxic T lymphocytes and natural killer cells. Severe immunodeficiency and generalized macrophage activation can often be detected in the background of this life threatening disorder. It is classified as a primary immunodeficiency. Functional abnormalities of the perforin protein or defects in granule secretory mechanisms are caused by gene mutations in most cases. Diagnostic criteria of hemophagocytic lymphohistiocytosis are the following: fever, splenomegaly, cytopenias affecting at least two of the 3 lineages in peripheral blood, hypertriglyceridemia and hyperferritinemia, elevated serum level of soluble interleukin-2 receptor (sCD25), hypofibrinogenemia, hemophagocytosis in bone marrow and decreased cytotoxic T cell and natural killer cell activity. In this case report the authors summarize the utility of functional flow cytometry in the diagnosis of hemophagocytic lymphohistiocytosis. Using flow cytometry, elevated intracellular perforin content, decreased killing activity of cytotoxic T cells and natural killer cells, and impaired cell surface expression of CD107a (LAMP1 protein) from in vitro stimulated blood lymphocytes were detected. Abnormal secretion of perforin was also demonstrated. Genetic testing revealed mutation of the MUNC 13-4 gene, which confirmed the base of the abnormal flow cytometric findings. This case report demonstrates the value of functional flow cytometry in the rapid diagnosis of genetically determined hemophagocytic lymphohistiocytosis, a condition in which early diagnosis is critical for optimal management. The authors emphasize the significance of functional flow cytometry in the differential diagnosis of immunodeficiencies. Orv. Hetil., 2014, 155(10), 389–395.

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