Acutephase

Acute-phase, in medical use, refers to the acute-phase response, a rapid, systemic reaction of the body to infection, injury, or other inflammatory stimuli. The primary aim is to limit tissue damage, contain the source of the insult, and initiate repair. The response is typically transient and self-limiting when the underlying cause is resolved.

The initiation of the acute-phase response is driven by pro-inflammatory cytokines, especially interleukin-1, interleukin-6, and tumor necrosis factor alpha, produced by activated macrophages and other cells. These signals stimulate the liver to produce acute-phase proteins and to alter the synthesis of other mediators. Key acute-phase proteins include C-reactive protein, serum amyloid A, fibrinogen, haptoglobin, ceruloplasmin, and hepcidin. C-reactive protein levels rise quickly, often within 6 to 24 hours of stimulus, and peak around 48 hours, whereas the erythrocyte sedimentation rate rises more slowly, reflecting increased fibrinogen and other plasma changes.

Functions of acute-phase proteins are diverse. They participate in pathogen recognition and clearance, opsonization, and complement activation; they influence iron metabolism through hepcidin; and they contribute to coagulation and tissue repair. Fever, leukocytosis, and metabolic alterations are coordinated components of the broader acute-phase response.

Clinically, measurement of acute-phase markers such as CRP and ESR is used to assess and monitor inflammatory activity, infection, autoimmune disease activity, and response to therapy. The response typically declines as the underlying cause is treated, but persistent activation can indicate chronic inflammatory states or other serious conditions.