Immunohistochemical detection of CCR2 and CX3CR1 in sepsis-induced lung injury

Sepsis is a systemic inflammatory disease with high mortality. In the present study, we immunohistochemically examined CCR2 and CX3CR1 expression in sepsis-induced lung injury, and discussed its availability for the postmortem diagnosis of sepsis. Lung samples were obtained from different lung lobes of nine sepsis and eight control cases with postmortem intervals between 12 and 48 h. Immunohistochemically, mononuclear cells recruited into the lungs expressed CCR2 and CX3CR1 in both sepsis and non-septic groups. In double-color immunofluorescence analysis, CCR2- or CX3CR1-positive cells could be identified as CD68-positive macrophages. Moreover, most of CD68-positive macrophages expressed both CCR2 and CX3CR1. Morphometrically, the average of CCR2- and CX3CR1-positive macrophages was significantly increased in sepsis group, compared with control group (sepsis vs. control: 41.6 ± 1.3% vs. 8.0 ± 0.4% in CCR2; 36.2 ± 1.3% vs. 9.2 ± 0.4% in CX3CR1). These observations implied that CCR2- or CX3CR1-positive macrophages were recruited into the lungs under several pathological conditions. In particular, their recruitment might be more evident in sepsis. Moreover, from the forensic aspects, immunohistochemical detection of CCR2 and CX3CR1 expression in the lungs can be considered as valuable diagnostic tools for the postmortem diagnosis of sepsis.