acute-phase response

The acute-phase response is a nonspecific defense mechanism that helps the body fight infection. It is part of the innate immune system and occurs more rapidly than acquired immune responses, though it does not provide lasting immunity.12

When a pathogen invades, cells like macrophages release signaling proteins called cytokines, such as interleukin-1 (IL-1) and interleukin-6 (IL-6). These cytokines can induce fever by affecting the brain's hypothalamus, which is beneficial as many bacteria grow best at lower temperatures.1

The acute-phase response also stimulates liver cells to release acute-phase proteins into the bloodstream. These proteins bind to bacteria, activating complement proteins that destroy pathogens. Unlike antibodies, acute-phase proteins attack a wide range of microorganisms indiscriminately. Additionally, interleukins increase the number of neutrophils and eosinophils, which are white blood cells that help combat infection. This response works alongside the inflammation response, which also brings phagocytic cells to the site of infection to clear pathogens and cellular debris.132