To investigate whether the increase in the neutrophil percentage and the neutrophil–T cell ratios observed in the spleen of C57BL/6 mice on day 4 post-infection was also present in the peripheral blood, we assessed the percentages of neutrophil, T cells, and their subpopulations (CD4 T cells and CD8 T cells) in the blood of BALB/c and C57BL/6 mice. This evidence concerns the gene CD4 and infection.