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RMT in the making! The body's defense system. Antibodies and Antigens working together!
1. Immunoglobulins (Antibodies)
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IgG (Most Abundant - 80%)
- Only Ig that crosses placenta
- Secondary immune response
- Opsonization, neutralization
IgM (Largest, First Response)
- Pentamer structure
- Primary immune response (acute infection)
- Cannot cross placenta
- ABO antibodies are IgM
IgA (Mucosal Defense)
- Found in secretions (saliva, tears, breast milk)
- Dimer with secretory component
- First line defense at mucosal surfaces
IgE (Allergies & Parasites)
- Allergic reactions, anaphylaxis
- Binds to mast cells and basophils
- Defense against parasites
2. Serological Tests
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Hepatitis Markers
- HBsAg: Active infection (surface antigen)
- Anti-HBs: Immunity (from vaccine or recovery)
- Anti-HBc IgM: Acute infection
- HBeAg: High infectivity
HIV Testing
- Screening: ELISA/EIA (4th gen detects p24 Ag)
- Confirmatory: Western Blot
- Window period: 2-4 weeks (Ag), 3-12 weeks (Ab)
Dengue Tests
- NS1 Antigen: Day 1-7 (early detection)
- IgM: Day 5+ (recent infection)
- IgG: Secondary infection, past exposure
Syphilis Tests
- Non-treponemal: RPR, VDRL (screening, can be false+)
- Treponemal: FTA-ABS, TPHA (confirmatory, specific)
💡 Board Exam Tips - Immunology
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Only IgG crosses the placenta
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IgM = Primary/Acute response, IgG = Secondary/Chronic
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HBsAg positive = Currently infected with Hepatitis B
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