Although CXCL13 expression was impaired early after infection, the total amount of B cells in the lungs was not significantly altered at the time iBALT was present (Figure 1C), suggesting that it is not recruitment of B cells to the lungs that is impaired in Il1r1−/− mice but that the B cells in the lung fail to cluster into organized iBALT structures. This evidence concerns the gene IL1R1 and infection.