IL-6 and Its Soluble Receptor Orchestrate a Temporal Switch in the Pattern of Leukocyte Recruitment Seen during Acute Inflammation

During acute inflammation, leukocyte recruitment is characterized by an initial infiltration of neutrophils, which are later replaced by a more sustained population of mononuclear cells. Based on both clinical and experimental evidence, we present a role for IL-6 and its soluble receptor (sIL-6R) in controlling this pattern of leukocyte recruitment during peritoneal inflammation. Liberation of sIL-6R from the initial neutrophil infiltrate acts as a regulator of CXC and CC chemokine expression, which contributes to a suppression of neutrophil recruitment and the concurrent attraction of mononuclear leukocytes. Soluble IL-6R-mediated signaling is therefore an important intermediary in the resolution of inflammation and supports transition between the early predominantly neutrophilic stage of an infection and the more sustained mononuclear cell influx.