Innate immune cells are the body's first line of defense against infections and foreign invaders. They respond quickly to threats without needing prior exposure to them. Key types of innate immune cells include macrophages, neutrophils, and natural killer cells, which work together to identify and eliminate pathogens. These cells recognize common features of pathogens, such as bacteria and viruses, through pattern recognition receptors. Once activated, innate immune cells can engulf and destroy invaders, release signaling molecules to recruit other immune cells, and initiate the inflammatory response, helping to protect the body from disease.