Table 1 Biologic functions of some common acute phase proteins (APP)

C-Reactive protein (CRP)

Opsonises infectious agents to activate complement and phagocytosis. Up- or downregulates cytokine production and chemotaxis. Has both pro-inflammatory and anti-inflammatory effects.

Serum amyloid P

Analogue of CRP in some animals.

Serum amyloid A (SAA)

Chemotaxis of polymorphonuclear cells, monocytes, and T cells. Downregulates the inflammatory process. Binds cholesterol and modulates innate immune reactions. Known as an innate immunity opsonin.

Albumin

Binds fatty acid, bilirubin. Regulates osmotic pressure.

Haptoglobin (Hp)

Dampens oxidative damage due to haemolysis by binding free haemoglobin. Bacteriostatic. Immunomodulator. Angiogenesis and chaperone activity.

α₁-Acid glycoprotein (AGP)

Binds and inhibits LPS. Downregulates neutrophils and complement. Transports molecules in plasma. Immunomodulator of white blood cells. Reduces apoptosis of bovine monocytes. Antibacterial.

α₁-macroglobulin

Protease inhibitor; removes enzymes released during injury.

Lipopolysaccharide binding protein (LBP)

Binds LPS, activates innate immunity. Modulates biological activity of immune cells. Opsonin.

Inter α trypsin inhibitor H4 (ITIH4)

Protease inhibitor.

Fetuin (α HS glycoprotein)

Bone growth, foetal development

α₁ Anti proteinase (Anti trypsin)

Protease inhibitor

Major acute phase protein (Porcine) (pig-MAP)

Trypsin inhibitor (porcine species).

Ceruloplasmin

Scavenges free radicals.

Paraoxanase

Oxidase inhibitor.

Lipoprotein

Lipid transport.

Retinal binding protein

Transport of vitamin A.

Mammary-associated serum amyloid A3

Milk APP.

Fibrinogen

Precursor for fibrin, tissue repair.

Transferrin

Positive APP in avian species and negative in mammals. Immunomodulator, protein transport, tissue protection from damage from inflammation.