Which type of blood cells is primarily responsible for defending the body against pathogens such as bacteria, viruses, and fungi?

White blood cells, or leukocytes, play a crucial role in the immune system by defending the body against pathogens including bacteria, viruses, and fungi. They are equipped with various mechanisms to identify and neutralize these harmful invaders. There are several types of white blood cells, such as neutrophils, lymphocytes, and monocytes, each with specific functions in immune response.

For instance, neutrophils are often the first responders to infections, while lymphocytes, such as T cells and B cells, are critical for adaptive immunity, providing targeted responses and memory against specific pathogens. This specialized function of white blood cells makes them essential for maintaining the body’s health and fighting off infections.

In contrast, red blood cells are primarily responsible for transporting oxygen to tissues and removing carbon dioxide, platelets are involved in blood clotting and wound healing, and stem cells are undifferentiated cells that can develop into various types of cells, but they do not have a direct role in immune defense. Thus, the correct answer emphasizes the unique and critical function of white blood cells in immunity.