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Systemic Lupus Erythematosus

Nicholas DelVecchio

Introduction

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Systemic Lupus Erythematosus (SLE) is an autoimmune disorder commonly affecting the skin, musculoskeletal, renal, neurological, haematological, cardiovascular, and respiratory systems (1). It is characterized by widespread inflammation, autoantibody production, and immune complex deposition. While SLE affects multiple major organ systems in the body, lupus nephritis is the leading cause of death. Approximately two million people suffer from SLE with the majority of cases being women, with a female to male ratio of 9:1. African American, Hispanic, Asian, and Native American women are more likely to get SLE than Caucasian women (4).

 

The exact pathological mechanisms of SLE is unknown, and the cause of SLE is known to have multiple factors involved, including multiple genes, sex hormones, and environmental factors like sunlight, drugs and infections (5).  In SLE, immune homeostasis is impaired, and both T and B cells acquire abnormal characteristics in terms of activation, cytokine production, and proliferative potential (4). SLE can manifest with the appropriate genetic background, presence of immune triggers, and effective immune system activation. Disease-specific antibodies may circulate for up to five years before the first clinical signs of organ involvement in the disease (5).

 

Apoptosis is a programmed cell death and occurs during various biological processes.  Phagocytes then clear out the dead cells from tissues (2). A core hypothesis for SLE pathogenesis implicates poorly cleared or excessively produced apoptotic blebs as a constant source of partially degraded nucleosomes (5). Nuclear autoantigens targeted in SLE are clustered in blebs at the surface of apoptotic cells (2). Impaired clearance of dying cells in SLE may explain the accumulation of apoptotic cells in tissues, while secondary necrosis of these cells might contribute to the chronic inflammation that is seen in this disease (5). Apoptosis induced modified nuclear autoantigens are exposed to the immune system and recognized as non-self-antigens causing a danger signal. Plasmocytic dendritic cells respond to nucleic acid-containing immune complexes by producing type I interferon IFN-α. Ultimately, these processes result in an immunogenic response and the formation of autoantibodies to the modified nuclear autoantigens

(2).

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Symptoms

 

Symptoms of System Lupus Erythematosus, SLE, include:

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  • Fatigue

  • Skin Rashes

    • Butterfly rash across the face is common among SLE patients.

  • Fevers

  • Pain and Swelling of Joints

    • Similar to arthritis pain

 

These symptoms can occur all at once, spontaneously for a period of time, and go away suddenly. These periods are called flares and can happen years apart, some experiencing them more frequently than others. What triggers flares is unknown, but environmental factors and stress seem play a role.

 

Other symptoms SLE patients may experience include:

  • sensitivity to the sun

  • oral ulcers

  • arthritis

  • lung problems

    • plural effusions

  • Heart problems

    • Myocarditis

  • Kidney problems

    • Interstitial arthritis

  • Seizures

  • Psychosis

  • Blood cell and immunological disorders

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Cell Signaling

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Apoptosis occurs, whether following infection or just normal cell death. DNA and RNA are subject to modification by proteases, caspase, and endonucleases. Apoptotic blebs containing modified nuclear material, accumulate on surface of apoptotic cell. Normally, phagocytes would remove blebs and cells, in SLE, phagocytes may be negatively affected and will not clear up blebs before nuclear material is released. Nuclear material is released and marked as antigen. Dendritic cells pick it up and present it to T cell, which then presents it to B cell for activation. B cell release auto antibodies which bind to nuclear auto antigens. Auto antibody/antigen complex is collected by basement membrane. Endosome containing nuclear antigen activate Toll like receptor-3, TLR-3. This then activates TIR-domain-containing adapter-inducing interferon-β, TRIF, which initiates a signaling cascade. TNF receptor-associated factor, TRAF 3, mediates the signal to Interferon regulatory factor 3, IRF3. This binds directly to the DNA which up regulates the transcription of interferons and inflammatory cytokines, leading to pain and inflammation.

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Treatments

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  • No cure, therefore you treat the symptoms

  • immunosuppressants

  • corticosteroids.

  • analgesics

 

Further research

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A good target would be the apoptotic blebs containing autoantigen. Developing a way of increasing the phagocytosis of these blebs before they can be presented to immune cells.

References

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  1. Magro, R., & Borg, A. A. (2018). Characterisation of Patients with Systemic Lupus Erythematosus in Malta: A Population Based Cohort Cross-Sectional Study. BioMed research international, 2018, 2385386. doi:10.1155/2018/2385386

  2. Munoz LE, van Bavel C, Franz S, Berden J, Herrmann M, van der Vlag J. Apoptosis in the pathogenesis of systemic lupus erythematosus. Lupus. 2008;17(5):371–375. doi: 10.1177/0961203308089990

  3. Shrivastav Meena, Niewold Timothy. Nucleic Acid Sensors and Type I Interferon Production in Systemic Lupus Erythematosus. Frontiers in Immunology. 2013; 4:319 https://www.frontiersin.org/article/10.3389/fimmu.2013.00319 

  4. Singh, R. P., Waldron, R. T., & Hahn, B. H. (2011). Genes, tolerance and systemic autoimmunity. Autoimmunity reviews, 11(9), 664–669. doi:10.1016/j.autrev.2011.11.017

  5. Tiffin, N., Adeyemo, A., & Okpechi, I. (2013). A diverse array of genetic factors contribute to the pathogenesis of systemic lupus erythematosus. Orphanet journal of rare diseases, 8, 2. doi:10.1186/1750-1172-8-2

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