What is the difference between humoral and cellular adaptive immunity?

• A. Humoral immunity uses T cells; cellular immunity uses B cells
• B. Humoral uses B cells and antibodies; cellular uses T cells
• C. Humoral is innate; cellular is adaptive
• D. They are identical

Answer: (B)

The difference lies in which cells drive the response and where the defense acts. Humoral immunity uses B lymphocytes, which mature into plasma cells that secrete antibodies into the bloodstream and other body fluids. These antibodies bind to pathogens or toxins outside cells, neutralizing them directly and tagging them for destruction by other immune cells or the complement system. This arm is especially effective against extracellular bacteria, viruses, and toxins.

Cellular (cell-mediated) immunity, on the other hand, is driven by T lymphocytes. Helper T cells coordinate the immune response and support other cells, while cytotoxic T cells kill cells that are infected with intracellular pathogens or have become abnormal. They recognize antigens presented on MHC molecules by infected cells and destroy those cells to stop the infection. Memory T cells also form to respond more quickly in the future.

So, the best description is that humoral immunity uses B cells and antibodies, while cellular immunity uses T cells.