Effect of multi-walled carbon nanotube (MWCNT) inhalation on pulmonary inflammatory cell influx at 0 d post-exposure. Polymorphonuclear cells, an indication of pulmonary inflammation, were measured from reconstituted pellets of the bronchoalveolar cellular fraction. H = high dose; M = middle dose; L = low dose. Data are expressed as percent (%) PMN from a total of 300 cells counted slides from cytospins. *p<0.05 vs. respective sham.