Fig 3D: P = 0.006, 6 hours; P = 0.013, 12 hours) were significantly reduced in the TLR4-deficient mice after S. pneumoniae infection compared to the wild-type mice. In addition, TLR4-deficient mice exhibited more serious lung histopathological injury (Fig 2A–2C and Fig 4A–4C). Taken together, loss of TLR4 reduced the host resistance to S. pneumoniae, indicating its involvement in the host immune response to pneumococcal infection. The gene discussed is TLR4; the disease is pneumococcal infection.