Which cells are primarily responsible for defending the body against infection and can increase rapidly during serious infection?

• A. Lymphocytes
• B. White Blood Cells
• C. Platelets
• D. Plasma

Answer: (B)

White blood cells are the body's main defenders against infection. They patrol the blood and tissues, recognize invading pathogens, and attack them through methods like engulfing bacteria, destroying infected cells, and coordinating broader immune responses. When infection is serious, the body ramps up production and releases more white blood cells from the bone marrow, causing their numbers to rise quickly to mount a stronger defense. Among these cells, some respond faster to acute infections, while others provide targeted, longer-term immunity, but the overall increase in white blood cells is a key indicator of the immune system at work. Platelets concern clotting, and plasma is the fluid that carries antibodies, but the rapid, active defense against infection comes from white blood cells.