What is the primary effect of IL-6 in the acute phase response?

Interleukin-6 (IL-6) plays a crucial role in the acute phase response, which is the body's immediate reaction to injury or infection. One of its primary effects is the stimulation of acute phase protein synthesis, particularly in the liver. During the acute phase response, IL-6 prompts hepatocytes to produce a variety of proteins such as C-reactive protein (CRP), fibrinogen, and serum amyloid A. These proteins are essential for modulating inflammation, enhancing phagocytosis, and aiding in the body's defense against pathogens.

Additionally, the elevation of these acute phase proteins contributes to systemic responses such as fever and the recruitment of immune cells to sites of injury or infection, all of which are vital for an effective inflammatory response. This mechanism underscores IL-6's role as a pro-inflammatory cytokine, emphasizing its significance in mediating the acute phase response rather than inhibiting it or directly promoting apoptosis. Therefore, the stimulation of acute phase protein synthesis is the most accurate representation of IL-6's primary effect in this context.