Compared to animals infected with a low dose of LCMV-DOC (200 PFU), mice infected with intermediate (2×104 PFU) or high (2×106 PFU) virus doses exhibited markedly increased proportions of Treg cells in spleen and peripheral organs that amounted up to 20% of all CD4+ T cells at 15 days post infection (Figure 1B, C). This evidence concerns the gene CD4 and infection.