Which cell type is responsible for producing antibodies in humoral immunity?

• A. B lymphocytes
• B. T lymphocytes
• C. Macrophages
• D. Platelets

Answer: (A)

Humoral immunity relies on antibodies produced by B lymphocytes. When a B cell encounters its specific antigen and receives help from a T helper cell, it differentiates into plasma cells that secrete large quantities of antibodies. These antibodies circulate to neutralize pathogens, block infection, aid in opsonization for phagocytosis, and activate the complement system. Thus, the cell type responsible for antibody production is the B lymphocyte lineage, especially the plasma cells they become. In contrast, T lymphocytes drive cellular immunity, macrophages mainly present antigens and phagocytose, and platelets are mainly involved in clotting rather than antibody production.