Which antibody is typically the first to respond to an infection?

The antibody that is typically the first to respond to an infection is IgM. When the body is exposed to a new pathogen, IgM is produced rapidly as part of the primary immune response. It plays a crucial role in the early stages of an immune response due to its pentameric structure, which allows it to effectively bind to multiple antigens and initiate the process of clumping pathogens together, making it easier for other immune cells to target and eliminate them.

IgM is particularly effective in forming complexes that can activate the complement system, enhancing the body's ability to fight off infections. It acts as a first line of defense until other antibodies, such as IgG, which is produced later in the immune response, take over for longer-term immunity. Other antibodies, like IgA and IgD, are involved in different aspects of the immune system and do not typically respond as quickly as IgM during an initial infection.