CD4+IFNγ-/- T cell recipients that survived the infection and were treated with isotype antibody were almost negative for R. typhi. The bacteria were generally not detectable in the liver and lung of these animals while low copy numbers were detectable in the spleen (1.12±1.12 copies) and brain (64.93±19.13 copies) at the end of the experiment. The gene discussed is IFNG; the disease is infection.