T-cells are needed by the immune system to:

• A. To fight disease
• B. To regulate blood pressure
• C. To digest fats
• D. To transport oxygen

Answer: (A)

T-cells are part of the body's adaptive immune system and are essential for fighting disease. They recognize specific pathogens and coordinate the immune response: helper T-cells activate B-cells to produce antibodies and help cytotoxic T-cells destroy infected cells, while regulatory T-cells modulate the response to prevent overactivity. This targeted, cell-mediated action is why T-cells are needed to defend against disease. They aren’t responsible for regulating blood pressure, digesting fats, or transporting oxygen—those roles lie with other systems and molecules in the body.