Macrophages from BALB/c and CBA/Ca mice differ in their cellular responses to Streptococcus pneumoniae.

In a mouse model of pneumonia caused by Streptococcus pneumoniae, differences in the timing and vigor of the host inflammatory response have been associated with susceptibility to invasive disease. BALB/c and CBA/Ca mice are known to be resistant and susceptible to acute pneumococcal disease, respectively. In this study, we have demonstrated that BMM from BALB/c and CBA/Ca mice differ in their expression and regulation of TLR9 in response to S. pneumoniae. We have also shown that BMM from CBA/Ca mice failed to fully activate p38, NF-kappaB, and ERK 1/2 signaling pathways, resulting in reduced secretion of TNF-alpha and CCL5 in response to this pathogen. In addition, we have established that S. pneumoniae induced significant cell death in BMM from CBA/Ca mice. These findings indicate that variations between the two strains are likely to reflect differences in macrophage responses to the pathogen.