What are cells that fight bacteria and other foreign substances known as?

• A. Platelets
• B. Red blood cells
• C. Leukocytes
• D. Macrophages

Answer: (C)

Leukocytes, commonly referred to as white blood cells, play a crucial role in the immune system. Their primary function is to defend the body against infections and foreign invaders, such as bacteria, viruses, and other pathogens. These cells are vital for both recognizing and responding to threats, often by engulfing pathogens, producing antibodies, and orchestrating the immune response.

In contrast, platelets are primarily involved in blood clotting and do not engage directly in immune defense. Red blood cells are responsible for transporting oxygen throughout the body, which is essential for cellular metabolism but is unrelated to fighting infections. Macrophages, while effective in combating foreign substances, are a specific type of leukocyte and do not encompass the entire group. Thus, leukocytes represent the broader category of immune cells, making them the correct answer in this context.