T-Lymphocytes are white blood cells with a role in what type of immunity?

• A. They are the primary producers of antibodies.
• B. They are baked into the bone marrow.
• C. They are a type of white blood cell involved in humoral immunity.
• D. They are white blood cells with a role in cell-mediated immunity.

Answer: (D)

T lymphocytes are central to cell-mediated immunity. They do not produce antibodies—the job of B cells in humoral immunity. T cells mature in the thymus, not the bone marrow. They include cytotoxic T cells that kill infected or abnormal cells and helper T cells that coordinate the immune response by activating other immune cells. Their primary role is recognizing and responding to cells that are infected or otherwise altered, rather than secreting antibodies.