Half-life of human or mouse anti-F1 and anti-V mAbs given passively to mice An ELISA as described above was used to detect the amount of human or mouse anti-F1 and anti-V mAbs present in mice over time. Briefly, F1-V protein (2 mg/ml in 0.2 M carbonate buffer, pH 9.4)) was used to coat a 96-well plate (Immulon 2HB) overnight at 4uC before washing and blocking. Two-fold dilutions of mouse serum taken retro-orbitally after i.p. administration of the mAb were made in 1X PBS with 1% BSA and 0.05% tween-20, added to plates and incubated for 1 hr at 37uC before washing. The amount of human or mouse anti-F1 or anti-V mAb binding to the antigens was detected by the addition of goat-anti-human or goat-anti-mouse IgG conjugated to HRP (Southern Biotechnology). The results from 3 mice at each time point for each mAb was performed in triplicate and were reported as the mean of the reciprocal of the highest dilution giving a mean OD of at least 0.1, which is at least twice the standard deviation (SD). Diagnostic value of triggering receptor expressed on myeloid cells-1 and C-reactive protein for patients with lung infiltrates: an observational study BACKGROUND: Differential diagnosis of patients with lung infiltrates remains a challenge. Triggering receptor expressed on myeloid cells (TREM)-1 is a neutrophil and monocyte receptor up-regulated during infection. The aim of this study was to evaluate the diagnostic accuracy of TREM-1 and of C-reactive protein (CRP) from patients with lung infiltrates to discern community acquired lung infections. METHODS: 68 patients admitted to a medical ward with acute respiratory illness were enrolled in the study. Neutrophil and monocyte TREM-1 expression were measured by flow cytometry, sTREM-1 by an enzyme immunoassay and C-reactive protein by nephelometry. Clinical pulmonary infection score was recorded. RESULTS: 34 patients were diagnosed with bacterial community acquired pneumonia (group A) and 34 with non-bacterial pulmonary disease (group B). Median serum TREM-1 concentration was 102.09 pg/ml in group A and lower than 15.10 pg/ml (p < 0.0001) in group B. Mean±SE neutrophil TREM-1 expression was 4.67 ± 0.53 MFI in group A and 2.64 ± 0.25 MFI (p = 0.001) in group B. Monocyte TREM-1 expression was 4.2 ± 0.42 MFI in group A and 2.64 ± 0.35 MFI (p = 0.007) in group B and mean±SE CRP was 18.03 ± 2 mg/ml in group A and 7.1 ± 1.54 mg/ml (p < 0.001) in group B. A cut-off of 19.53 pg/ml of sTREM-1 with sensitivity 82.6% and specificity 63% to discriminate between infectious and non-infectious pulmonary infiltrates was found. sTREM-1 at admission greater than 180 pg/ml was accompanied with unfavourable outcome. CONCLUSION: TREM-1 myeloid expression and sTREM-1 are reliable markers of bacterial infection among patients with pulmonary infiltrates; sTREM-1 is a predictor of final outcome. Early diagnosis of lung infections remains a challenge. There is no gold standard for diagnosing microbial infection as clinical and laboratory signs are neither sensitive nor specific enough, and microbiological studies often remain negative. The presence of a new infiltrate on plain chest radiograph is considered indicative for diagnosing pneumonia, especially when is supported by clinical and laboratory findings. However it is difficult to differentiate a chest infiltrate of bacterial origin from a chest infiltrate of non-bacterial origin solely based on radiological criteria [1] . The diagnosis of infection is not always clear in the acute setting in patients with respiratory tract disease and a surrogate marker of infection would be a major benefit in the diagnostic armamentarium. Many inflammatory mediators and acute phase reactants, like C-reactive protein (CRP) and procalcitonin, have been described as reliable markers of infection; however none are specific enough, since they are also increased in non-infectious inflammatory conditions [2] .