Mechanism of Autoimmunity: Understanding the Body's Immune Response

The immune system’s job is to identify and destroy threats (bacteria, viruses, cancer cells) while leaving your own tissues alone. This distinction is made through ‘self vs non-self’ recognition — trained during immune-cell development in the thymus and bone marrow. In autoimmune disease, this recognition breaks down: T-cells and B-cells that should have been eliminated during development escape into circulation and start attacking body tissues as if they were foreign. Specific mechanisms: (1) Molecular mimicry — a foreign antigen (from infection) closely resembles a self-antigen, causing cross-reactive attack; (2) Genetic predisposition — certain HLA gene variants (HLA-B27 in ankylosing spondylitis, HLA-DR4 in RA, HLA-DR3 in T1DM) make immune misrecognition more likely; (3) Environmental triggers — infections (Epstein-Barr virus linked to lupus, MS), smoking (worsens RA), UV light (triggers lupus flares), gut microbiome disruption (may drive IBD, RA); (4) Loss of regulatory T-cells (‘Tregs’) — normally keep autoreactive cells in check; when they fail, autoimmunity emerges. Once triggered, autoreactive B-cells produce autoantibodies (anti-CCP in RA, anti-dsDNA in lupus, anti-TPO in Hashimoto’s) that mark self-tissue for immune destruction, causing chronic inflammation and damage.

Common autoimmune conditions in India, ranked by prevalence: (1) Hashimoto’s thyroiditis (autoimmune hypothyroidism) — affects 8-15% of Indian women; anti-TPO antibody positive; treated with lifelong levothyroxine; (2) Rheumatoid arthritis — 0.5-1% of Indian adults; anti-CCP positive; requires DMARD therapy; (3) Type 1 diabetes — increasing in Indian children; autoimmune beta-cell destruction; insulin-dependent; (4) Psoriasis — 0.5-1% of Indians; genetic + environmental triggers; topical + systemic therapies; (5) Systemic Lupus Erythematosus (SLE) — 3-5x more common in women, especially 15-45 years; requires hydroxychloroquine ± immunosuppressants; (6) Vitiligo — 0.5-2% of Indians; melanocyte destruction; cosmetic and psychological impact; (7) Ankylosing spondylitis — young men predominantly; HLA-B27 positive in 90%; (8) Inflammatory bowel disease (Crohn’s + ulcerative colitis) — rising in India; requires GI specialist care; (9) Sjogren’s syndrome; (10) Multiple sclerosis (less common in India than West). Family clustering common — if first-degree relative has autoimmune disease, your risk of any autoimmune disease is 3-5x higher.

Autoimmune diseases arise from a combination of genetic susceptibility (30-50% of risk) and environmental triggers (50-70% of risk). You cannot change your genes, but you can modify environmental factors that trigger autoimmune activation: (1) Vitamin D adequacy — Indian population 70-80% deficient (NIN-ICMR data); adequate Vitamin D reduces risk of MS, T1DM, RA in observational studies; target 25-OH-D level 30-50 ng/mL through sun exposure + supplementation (2000-4000 IU/day); (2) Smoking cessation — smoking directly triggers RA in genetically susceptible individuals; smoking cessation reduces RA risk 30-50% over 20 years; (3) Gut health — probiotic-rich foods (dahi, kimchi, kefir), fibre-rich diet, avoid unnecessary antibiotics; disrupted gut microbiome linked to IBD, RA, T1DM; (4) Weight management — obesity worsens autoimmune outcomes; (5) EBV/mono infection — avoid in adolescence if possible (unrealistic but linked to MS, lupus); (6) Stress management — chronic severe stress may trigger flares; (7) Early treatment of triggering infections. Once autoimmune disease is established, focus shifts to preventing progression and maintaining remission through medications + lifestyle. Family history doesn’t guarantee disease — most people with genetic susceptibility never develop autoimmune illness.