Indeed, it has been more recently reported that NK and NKT cells are the earliest producer of IFN-γ in C57BL6 mice during T. brucei brucei AnTat1.1E infection, and that later in infection, IFN-γ is mainly produced by CD8+ and CD4+ T cells (18), supporting the notion that IFN-γ is produced by different subsets of leukocytes at different stages of infections. This evidence concerns the gene CD4 and infection.