Our observation that forced expression of fbpB increased thefrequency of Ag85B peptide 25-specific CD4+ T cells and reducedthe bacterial burden in the lungs (Figure 4D, 4E, and 4F), together with our observation that injectionof peptide 25 also increased activation of CD4+ effector T cellsat the site of infection (Figure 2Band 2C) suggested that providing antigen by injection of peptide 25might also result in improved immune control of infection. This evidence concerns the gene CD4 and infection.