Acute-phase protein

The acute-phase reaction characteristically involves fever, acceleration of peripheral leukocytes, circulating neutrophils and their precursors.

In response to injury, local inflammatory cells (neutrophil granulocytes and macrophages) secrete a number of cytokines into the bloodstream, most notable of which are the interleukins IL1, and IL6, and TNF-α.

[2] TNF-α, IL-1β and IFN-γ are important for the expression of inflammatory mediators such as prostaglandins and leukotrienes, and they also cause the production of platelet-activating factor and IL-6.

This is due to the ESR being largely dependent on the elevation of fibrinogen, an acute phase reactant with a half-life of approximately one week.

In contrast, C-reactive protein (with a half-life of 6–8 hours) rises rapidly and can quickly return to within the normal range if treatment is employed.

For example, in active systemic lupus erythematosus, one may find a raised ESR but normal C-reactive protein.