RAG2 and cutaneous leishmaniasis: However, MHCII−/−, RAG2−/−, and SCID mice are resistant to Leishmania amazonensis infection, with no macroscopic lesions, minimal cellular infiltrate, and reduced tissue parasite load [17], which suggests that the CD4+ T lymphocytes in the C57BL/6 mice contribute to the development of the lesion in cutaneous leishmaniasis caused by Leishmania amazonensis.