A protein that plasma cells manufacture and that helps the body defend itself against foreign bodies is an)

• A. Hormone
• B. Antibody
• C. Enzyme
• D. Antigen

Answer: (B)

Antibodies are proteins produced by plasma cells that defend the body against foreign substances by recognizing and binding to antigens. This binding neutralizes pathogens directly and marks them for attack by other parts of the immune system, such as phagocytes and the complement system. Plasma cells originate from activated B lymphocytes and specialize in secreting large amounts of antibodies during an immune response. In contrast, a hormone is a signaling molecule released by glands to regulate body processes; an enzyme is a catalyst that speeds up chemical reactions; and an antigen is a foreign substance that triggers an immune response, not the protective protein itself.