To confirm that conversion of CD4+CD25- cells into iTreg cells was due to activated Treg cells and not an artifact of co-culture conditions (IL2, LPS, ConA) or an indirect effect of FIV infection, Th cells were co-cultured with DiD stained CD4+CD25+ cells from FIV negative control cats treated prior to co-culture with IL2/LPS. This evidence concerns the gene IL2 and infection.