CCL5 and bacterial pneumonia: For example, MyD88−/− and TRIF−/− mice develop severe pneumonia due to the profound bacterial growth during Gram-negative pneumonia (K. pneumoniae, P. aeruginosa, and E. coli) in response to the impaired immune response, including the reduced generation of Th1 immune response (TNF-α, IL-6, and IL-8) and almost no neutrophil influx and regulated upon activation normal T Cells expressed and presumably Secreted (RANTES or CCL5) production (65–68).