The Biochemistry, Functions, And Clinical Importance Acute Phase Proteins: A Review

Abstract

Acute phase proteins (APPs) are a heterogeneous group of plasma proteins whose concentrations change markedly in response to inflammation, infection, tissue injury, and metabolic stress. Synthesized predominantly by the liver under the regulation of pro-inflammatory cytokines, APPs exhibit diverse biochemical structures and functions that extend beyond their traditional role as nonspecific inflammatory markers. They actively participate in innate immune defense, modulation of oxidative stress, regulation of protease activity, lipid and metal metabolism, and maintenance of tissue homeostasis. Key APPs—including C-reactive protein, serum amyloid A, haptoglobin, α1-antitrypsin, and ceruloplasmin—demonstrate distinct physiological roles and clinically relevant response kinetics that reflect underlying disease processes. Aberrant or persistent alterations in APP levels are implicated in the pathogenesis of chronic inflammatory disorders, cardiovascular disease, metabolic syndromes, infectious diseases, and organ dysfunction. Clinically, APPs remain indispensable tools for disease diagnosis, activity assessment, and prognostic evaluation, although limitations related to specificity and biological variability persist. This review synthesizes current advances in the biochemistry, physiological functions, and clinical significance of major acute phase proteins, emphasizing their evolving translational relevance in modern laboratory and clinical medicine.

Keywords:

Acute Phase Proteins, CRP, SAA, fibrinogen, haptoglobin, α1-acid, ceruloplasmin

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