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 IL4 and susceptibility to pneumonia measurement.