What type of immunity is characterized primarily by the action of antibodies in bodily fluids?

Humoral immunity is characterized primarily by the action of antibodies that are found in bodily fluids, such as blood and lymph. This type of immunity is mediated by B cells, which produce antibodies in response to specific antigens. These antibodies then circulate in the bloodstream, where they can recognize and neutralize pathogens like bacteria and viruses.

Humoral immunity plays a critical role in the body's defense mechanism by marking pathogens for destruction, preventing their entry into cells, and facilitating their elimination by other immune cells. This process is distinct from cell-mediated immunity, which primarily involves T cells and does not rely on antibodies but rather on direct cell interactions to combat infected or cancerous cells. Additionally, innate immunity refers to the body's first line of defense against pathogens and includes physical barriers and non-specific immune responses, while adaptive immunity encompasses both humoral and cell-mediated responses that develop over time based on exposure to pathogens.