IL6 and bacterial infectious disease: To understand the underlying causes of this lethality, we assessed i) histological damage scores of lung sections, ii) total cell numbers in bronchoalveolar lavage fluids (BALF), iii) bacterial burden in the lung and the spleen, vi) concentrations of total protein, and v) levels of pro-inflammatory cytokines (TNF-α and IL-6) in BAL fluids at 24 h following bacterial infection.