STAT1 and pulmonary fibrosis: In the present study, we showed that rMWCNTs or tMWCNTs caused similar acute neutrophilic inflammation in the lungs of either Stat1−/− or Stat1+/+ mice at one-day post-exposure, although only rMWCNTs caused elevated neutrophil counts in the BALF of mice at 21 days (Fig. 2) along with pulmonary fibrosis at 21 days (Fig. 7).