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. This evidence concerns the gene CALCA and leprosy.