The S-specific CD4+ and CD8+ T-cells in the blood and airways appeared to also be highly functional, expressing high levels of granzyme B. These S-specific CD4+ and CD8+ T-cells were restimulated after boost while they transitioned to a Trm phenotype, providing a critical line of defense for the control of respiratory infections 12, 13, 14. This evidence concerns the gene CD4 and respiratory tract infectious disorder.