Compared to control animals, treatment produced higher expression of TNF‐α, IFN‐γ, IL‐2, iNOS and lower expression of IL‐4, with decreased lung fibrosis and bacillary load; there was a higher inflammatory response manifested as a greater area of lung affected by pneumonia. The addition of niflumic acid was synergistic, with reduced bacillary load and increased TNF‐α. This evidence concerns the gene TNF and pulmonary fibrosis.