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      Ehrlichiosis Presenting as Hemophagocytic Lymphohistiocytosis in an Immunocompetent Adult

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          Abstract

          Hemophagocytic Lymphohistiocytosis (HLH) is a fatal, immunologic syndrome characterized by dysregulated tissue inflammation. HLH can be either primary or secondary; with the latter typically resulting from an infection. Diagnosis requires five or more of the following: fever, splenomegaly, cytopenia, hypertriglyceridemia, hemophagocytosis via biopsy, low natural killer (NK) cell activity, elevated ferritin and soluble CD25 level (sCD25). We present a case of HLH related to ehrlichiosis.

          In order to mount an effective immune response against microbes such as Ehrlichia chaffeensis, the host must have preserved NK cell function. Being that HLH Is characterized as a state of depleted NK cell function, It is crucial to investigate the role NK cell function has in the setting of HLH on the infectivity of Ehrlichia species.

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          Most cited references7

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          CD1: antigen presentation and T cell function.

          This review summarizes the major features of CD1 genes and proteins, the patterns of intracellular trafficking of CD1 molecules, and how they sample different intracellular compartments for self- and foreign lipids. We describe how lipid antigens bind to CD1 molecules with their alkyl chains buried in hydrophobic pockets and expose their polar lipid headgroup whose fine structure is recognized by the TCR of CD1-restricted T cells. CD1-restricted T cells carry out effector, helper, and adjuvant-like functions and interact with other cell types including macrophages, dendritic cells, NK cells, T cells, and B cells, thereby contributing to both innate and adaptive immune responses. Insights gained from mice and humans now delineate the extensive range of diseases in which CD1-restricted T cells play important roles and reveal differences in the role of CD1a, CD1b, and CD1c in contrast to CD1d. Invariant TCR alpha chains, self-lipid reactivity, and rapid effector responses empower a subset of CD1d-restricted T cells (NKT cells) to have unique effector functions without counterpart among MHC-restricted T cells. This review describes the function of CD1-restricted T cells in antimicrobial responses, antitumor immunity, and in regulating the balance between tolerance and autoimmunity.
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            Hemophagocytic lymphohistiocytosis: review of etiologies and management

            Hemophagocytic lymphohistiocytosis (HLH) covers a wide array of related life-threatening conditions featuring ineffective immunity characterized by an uncontrolled hyperinflammatory response. HLH is often triggered by infection. Familial forms result from genetic defects in natural killer cells and cytotoxic T-cells, typically affecting perforin and intracellular vesicles. HLH is likely under-recognized, which contributes to its high morbidity and mortality. Early recognition is crucial for any reasonable attempt at curative therapy to be made. Current treatment regimens include immunosuppression, immune modulation, chemotherapy, and biological response modification, followed by hematopoietic stem-cell transplant (bone marrow transplant). A number of recent studies have contributed to the understanding of HLH pathophysiology, leading to alternate treatment options; however, much work remains to raise awareness and improve the high morbidity and mortality of these complex conditions.
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              CD1-restricted T-cell responses and microbial infection.

              CD1, a conserved family of major histocompatibility (MHC)-like glycoproteins in mammals, specializes in capturing lipid rather than peptide antigen for presentation to T lymphocytes. The principles and mechanisms of this newly discovered immune strategy differ markedly from those governing classical MHC-peptide presentation. They might be exploited for the design of new lipid-based microbial vaccines and adjuvants.
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                Author and article information

                Contributors
                Journal
                IDCases
                IDCases
                IDCases
                Elsevier
                2214-2509
                12 May 2020
                2020
                12 May 2020
                : 20
                : e00813
                Affiliations
                [a ]University of Missouri-Columbia, Department of Medicine, 1 Hospital Dr, Columbia, MO 65201, United States
                [b ]University of Missouri-Columbia, Department of Medicine, Division of Infectious Diseases, 1 Hospital Dr, Columbia, MO 65201, United States
                [c ]University of Missouri-Columbia, Department of Medicine, Division of Pulmonary, Critical Care, and Environmental Medicine, 1 Hospital Dr, Columbia, MO 65201, United States
                [d ]University of Missouri-Columbia, Department of Medicine, Division of Infectious Diseases, 1 Hospital Dr, Columbia, MO 65201, United States
                Author notes
                [* ]Corresponding author. patelt@ 123456health.missouri.edu
                Article
                S2214-2509(20)30121-9 e00813
                10.1016/j.idcr.2020.e00813
                7235617
                a6a3d16f-c551-4956-8f9e-47c243d14daa
                © 2020 The Author(s)

                This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

                History
                : 6 May 2020
                : 8 May 2020
                : 8 May 2020
                Categories
                Article

                ehrlichiosis,hemophagocytic lymphohistiocytosis,human monocytic ehrlichiosis,tick-borne illness,secondary hlh

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