To further validate the specificity of an IFN-γ mediated reductions in ΔhisD bacillary counts, C57BL/6-IFN-γ knockout mice (B6 IFN-γ−/−) were infected with H37Rv, chisD and ΔhisD, along with a control infection in B6 mice. The gene discussed is IFNG; the disease is infection.