At the acute stage of infection, lung-infiltrating cells obtained from mice infected with strain M299 secreted significantly higher levels of pro-inflammatory cytokines (IL-1β), neutrophil-recruiting chemokine (MIP-2/CXCL2) and IL-17, than those infected with strain H37Rv, whereas the secretion of TNF-α, IL-6, G-CSF and KC induced by these strains was similar (Fig 6). Here, IL6 is linked to infection.