Instillation of diesel exhaust particles (DEP) causes transient pulmonary inflammation. (a) Representative photomicrograph of a cytocentrifuge slide prepared from bronchoalveolar lavage fluid (BALF) collected from a DEP-instilled animal 6 h after instillation. Neutrophils (open arrow) and alveolar macrophages (black arrow) containing particulate (purple arrow) are apparent. Diff-Quick™ staining, ×400 magnification. BALF was analysed for (b) total cell count, (c) neutrophils, (d) alveolar macrophages, (e) total protein (bicinchonic acid assay) and (f) interleukin-6 (IL-6). Non-instilled (open columns), saline-instilled (solid columns) and DEP-instilled (hatched columns) animals 6 and 24 h after instillation. Results are expressed as mean ± SEM (n = 4-8; data for non-instilled groups were pooled, n = 11) ***P < 0.001 DEP versus saline; two-way ANOVA followed by Bonferroni post-hoc test.