CD4 and infection: To examine whether the enhanced pulmonary protection induced by the Rv3131 subunit vaccine correlated with the generation of Rv3131-specific CD4+ or CD8+ T cells expressing effector cytokines, we evaluated the frequency of multifunctional T cells after in vitro stimulation with PPD (Supplementary Fig. S3) or Rv3131 (Fig. 5) at 4 and 10 weeks post-infection.