Autoimmunity is a condition in which the immune system mistakenly attacks the body’s own healthy tissues, thinking they are foreign invaders like viruses or bacteria. This leads to chronic inflammation, tissue damage, and a wide variety of autoimmune diseases.

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### 🧬 How does autoimmunity develop?

Under normal circumstances, the immune system has mechanisms of self-tolerance, meaning it can distinguish between “self” and “non-self.” In autoimmunity, this tolerance is broken, and immune cells begin to target the body’s own antigens (self-antigens).

Key mechanisms include:

- Loss of central tolerance (in thymus or bone marrow) - Defects in peripheral tolerance (failure to suppress rogue immune cells) - Molecular mimicry (pathogens resemble self-proteins) - Epitope spreading (initial immune attack expands to other self-antigens) - Aberrant activation of nucleic acid sensors, like TLRs or cGAS, leading to inappropriate immune signaling

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### 🔥 What happens in autoimmune diseases?

- Autoantibodies and autoreactive T cells target specific organs or systems - Chronic inflammation and tissue destruction - Often cyclical flares and remissions

Examples of autoimmune diseases: - Systemic lupus erythematosus (SLE) – affects skin, kidneys, joints, and brain - Rheumatoid arthritis – joints - Type 1 diabetes – pancreas (β-cells) - Multiple sclerosis – central nervous system (myelin) - Hashimoto's thyroiditis – thyroid gland

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### 🧪 Biomarkers and Diagnosis

- Autoantibodies (e.g., ANA in lupus, anti-TPO in Hashimoto’s) - Elevated cytokines (like IFN-α, IL-6) - Imaging and organ-specific tests

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### 💊 Treatment Approaches

- Immunosuppressants (e.g., corticosteroids, methotrexate) - Biologics (e.g., TNF inhibitors, anti-IL-6, anti-CD20) - Targeted therapies (e.g., JAK inhibitors, cGAS-STING inhibitors in trials) - Plasmapheresis (in severe cases)

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### 🧠 Take-home message

Autoimmunity is a malfunction of immune self-recognition, leading to inflammatory disease. While once considered incurable, modern therapies are increasingly targeted and personalized, offering better control and improved quality of life for patients.