CXCL8 and susceptibility to pneumonia measurement: Measurement of inflammatory cytokine levels using ELISA showed that IL-1β, IL-6, TNF-α, IL-2, IL-8, IL-12, and IFN-γ levels were significantly enhanced, while IL-10 levels were significantly reduced in the lung homogenates of Spn-induced pneumonia mice, compared with the normal mice (Fig. 4).