The host immune response is the body's defense mechanism against pathogens like bacteria, viruses, and fungi. It involves various cells and proteins that work together to identify and eliminate these harmful invaders. Key components include white blood cells, antibodies, and cytokines, which help recognize and attack foreign substances. When a pathogen enters the body, the immune system activates, triggering an inflammatory response. This process helps recruit more immune cells to the site of infection, enhancing the body's ability to fight off the threat. A well-functioning immune response is crucial for maintaining overall health and preventing disease.