Regarding Th17 cells, it was verified that patients with the tuberculoid form of leprosy had a high number of CD4 + IL-17 + cells, the opposite was observed in those with the lepromatous form. This information shows that Th1 and Th17 responses act in a way to collaborate in the containment of M. leprae.Persons with the lepromatous form exhibiting serum levels of IFN-γ above 50 pg/mL had a higher risk of manifesting neurological deficit. Unlike the other groups, individuals with the MB form exhibited an elevated IFN-γ load. The gene discussed is CD4; the disease is leprosy.