IFNG and leprosy: Injection of PPD into the skin of lepromatous leprosy patients leads to an emigration of IFN-γ secretion cells into the dermis, induction of HLA class II by KC, and accumulation of LCs in the dermis, accompanied by a reduced bacillary load.23 Lepromin reaction has been used as an important tool to differentiate between tuberculoid and lepromatous patients, since only the former are lepromin positive.