PTX3 and pneumococcal infection: Despite S. pneumoniae ability to stimulate PTX3 release from neutrophils, levels of the protein were similar in WT and neutropenic Csfr3−/− animals infected with S. pneumoniae. Bone marrow chimeras and conditional mice definitely demonstrated that stromal cells, and in particular endothelial cells, were a major source of PTX3 in this model of pneumococcal infection.