TNF-α expression and quantification in the lung. Immunohistochemical expression of TNF-α was detected using anti-TNF-α antibody in the lung sections from controls (A-B), one day (C-D) exposed rats without and with E. coli LPS challenge respectively, five day exposed rats without E. coli LPS challenge (E) and with E. coli LPS challenge (picture not shown). TNF-α expression in the airway epithelium (arrows, A-E) is shown. F. Quantification of TNF-α protein using ELISA showed no significant difference among any of the groups (Figure 5, P > 0.05). Original magnification A-F: ×400 and micrometer bar = 50 μm.