S100A9 and bacterial pneumonia: To investigate the functional role of MRP8/14 in host defense during gram-negative pneumonia, we infected mrp14−/− and Wt mice with 104 viable K. pneumoniae and harvested lungs, blood, spleen and livers at predefined time points for quantitative cultures, seeking to collect data representative for local defense, at the primary site of infection, and subsequent dissemination.