White blood cells, or leukocytes, are a crucial component of the immune system. Their primary function is to defend the body against infections and foreign invaders, such as bacteria, viruses, and parasites. They achieve this through various mechanisms, including the production of antibodies, engulfing pathogens, and signaling other immune cells to respond to threats. There are several types of white blood cells, each with specialized roles, ensuring a well-coordinated immune response. Maintaining a balance of white blood cells is vital for overall health, as an excess or deficiency can lead to increased susceptibility to illness or autoimmune disorders.