The ESAT-6-specific IL-17-, IFN-γ-, TNF-α-, and IL-2-producing CD4+ T-cell population in the lungs and spleen was considerably larger than that in BCG-immunised and BCG-primed ESAT-6-boosted mice, and Ag-specific CD4+CD44+ T-cells in the lungs were expanded when compared to pre-infection numbers (Figure 4). This evidence concerns the gene CD4 and infection.