In fact, a gene expression analysis of lung homogenates from wildtype and IL-17A−/− mice revealed that whereas Il12p40, Il23p19, Il21, and Il22 were comparably induced after infection with an elevated dose of Mtb, the expression of the Il17f gene was significantly upregulated in the absence of IL-17A on Day 161 and tended to be higher on Day 199 post-infection (Figure 7A; Figure S2A–C). Here, IL21 is linked to infection.