Which term is a protein produced by B cells to bind antigen?

• A. Allergen
• B. Anaphylaxis
• C. Antibody
• D. Type I Hypersensitivity

Answer: (C)

Antibody is the protein produced by B cells that binds antigen. When B cells are activated, they differentiate into plasma cells that secrete immunoglobulins into the circulation. Each antibody has a variable region formed to fit a specific antigen epitope, so it can neutralize the threat, tag it for destruction (opsonization), or activate other immune components like the complement system. The terms you listed relate to allergic reactions rather than a product of B cells: an allergen triggers IgE-mediated responses in susceptible individuals, anaphylaxis is a life-threatening allergic reaction, and Type I Hypersensitivity describes that immediate allergy mechanism.