The major function of the immune system is to protect the body from pathogens, including viruses, bacteria, and parasites. It does this through a complex network of cells, tissues, and organs that work together to identify and eliminate foreign invaders. Key components include white blood cells, antibodies, and the lymphatic system. The immune response can be innate (rapid and nonspecific) or adaptive (slower but targeted), providing long-term immunity. A well-functioning immune system is essential for maintaining health and preventing diseases.