Micro & Immunology · single question
Which T-helper cell subtype is responsible for coordinating the immune response against EXTRACELLULAR pathogens (humoral immunity)?
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Correct answer: B. Th2
Th2 cells coordinate humoral (antibody-mediated) immunity against extracellular pathogens (parasites, allergens, bacteria in extracellular space). Th2 secretes IL-4, IL-5, IL-13 which stimulate B cells to produce antibodies, activate eosinophils, and promote IgE responses. Th1 cells coordinate cellular immunity (intracellular pathogens). Th17 cells coordinate responses against fungal and extracellular bacterial infections at mucosal surfaces.
- A. ❌ Th17 cells are involved in defense against extracellular bacteria and fungi at mucosal barriers, and contribute to autoimmune diseases.
- B. ✅ CORRECT – Th2 cells drive humoral immunity (antibody production) against extracellular pathogens through IL-4, IL-5, and IL-13 secretion.
- C. ❌ Th9 cells are a less well-defined subset involved in anti-parasitic responses and allergic inflammation.
- D. ❌ Th1 cells coordinate cellular (CMI) immunity against intracellular pathogens using IFN-γ and IL-2.
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