IgA in saliva primarily functions to:

Correct answer: D. Neutralize bacterial antigens and prevent colonization (antibacterial)

• A. IgE (not IgA) is responsible for allergic (Type I hypersensitivity) reactions.
• B. Complement activation is primarily a function of IgG and IgM — not IgA.
• C. T-cell stimulation is a function of antigen-presenting cells and cytokines — not IgA.
• D. Correct. Secretory IgA (sIgA) is the predominant immunoglobulin in saliva. It acts as the first line of defense in the oral cavity by binding to bacteria and viruses, preventing their adherence to mucosal surfaces and inhibiting their colonization. It has antibacterial and antiviral properties.