Which arm of the immune system is primarily responsible for antibody production by B cells?

• A. Innate immune system
• B. Cellular immunity
• C. Humoral immunity
• D. Complement system

Answer: (C)

Antibody production by B cells is the hallmark of humoral immunity. In this part of the adaptive immune response, B lymphocytes mature and, upon encountering antigens, differentiate into plasma cells that secrete antibodies. These antibodies circulate in blood and lymph, binding to pathogens or toxins, neutralizing them, and marking them for attack by other immune cells. This contrasts with cellular immunity, driven by T cells that orchestrate responses and kill infected cells, and with the innate immune system, which provides rapid, non-specific defense without producing antibodies. The complement system consists of proteins that amplify immune responses and can be activated by antibodies, but it does not produce antibodies itself.