Preparation of heat-killed K. pneumoniae
K. pneumoniae was purchased from ATCC (Manassas, Virginia) and grown overnight in brain heart infusion (BHI) broth (Eiken chemical, Tochigi, Japan) at 37°C. The bacterial number was determined by the absorbance at 600 nm (0.1=1x108/ml). K. pneumoniae was subjected to incubation at 70°C for 30 minutes to generate heat-killed K. pneumoniae .