The reported results of the present study are the first to our knowledge that evaluate the diagnostic value of TREM-1 among patients with lung infiltrates to discriminate CAP. They also disclose a relationship between levels of circulating sTREM-1 and causative pathogens. More precisely, infections caused by Streptococcus pneumoniae, Sthaphylococcus aureus and Haemophilus influenzae were accompanied by greater levels of sTREM-1 and by greater expression of TREM-1 on neutrophils than infections caused by other pathogens. Although it may be hypothesized that Gram-positive cocci and H. influenzae are strong inducers of TREM-1 expression, it should be emphasized that TREM-1 is one PRR, the exact agonist of which remains to be found [29, 31] .