In IFNγ KO C57BL/6 mice inoculated with L. (V.)guyanensis PLR6 isolate, lesions developed faster than in mice of the same strain inoculated with L. (V.)braziliensis (Figure 4(a)) and dissemination of parasites to the contralateral paw (increased thickness) was apparent on the 6th week after infection when the infected footpad began to ulcerate (data not shown). The gene discussed is IFNG; the disease is infection.