What are leukocytes?

• A. Red blood cells
• B. Plasma
• C. White blood cells that cause infection in the body
• D. Platelets

Answer: (C)

Leukocytes are white blood cells—the immune system’s frontline sentinels that defend the body against infection. They circulate in blood and can move into tissues to attack invading microbes, viruses, and other pathogens. Different types work in concert: neutrophils and macrophages phagocytose (eat) invaders, lymphocytes (B and T cells) coordinate targeted immune responses and produce antibodies, while other leukocytes participate in inflammation and allergic responses. This sets them apart from red blood cells (which carry oxygen), plasma (the liquid component of blood), and platelets (which help with clotting). So, leukocytes are the white blood cells responsible for protecting the body from infections.