Taken together, these data revealed that although both CD4 and CD8 T cells were primed through vaccination, there was an increased recruitment and proliferation of the CD4 T cells as compared to the CD8 T cells suggesting that this subset may be primarily involved in the recall response that results in early control of bacterial replication in vaccinated mice, and that increasing the CD4 T cell numbers in this stage of the infection is important. This evidence concerns the gene CD8A and infection.