Host defense refers to the immune system and other physiological mechanisms that protect an organism from microbial infection and other harmful agents. This research area focuses on understanding how the body detects and responds to pathogens, such as bacteria, viruses, and fungi, to prevent disease and maintain health. Researchers in the field of host defense study various aspects of the immune response, including the function of immune cells, the production of antibodies, and the signaling pathways that regulate immune activity. Additionally, they investigate how pathogens evade the immune system and develop strategies to enhance host defense mechanisms. Overall, research in host defense is essential for developing new therapies and vaccines to prevent and treat infectious diseases.