Immunity & infection
Neutrophils are known for their role in bacterial clearance and implication in pathogenesis of infectious diseases. However, recent reports have described that neutrophils have the ability to induce an anti-inflammatory response. Data obtained in our laboratory showed that during pneumonia caused by Streptococcus pneumoniae, neutrophils are able to produce IL-10. However the characteristics of these IL-10-producing neutrophils population in pneumococcal pneumonia remain unknown. In this study we have characterized the neutrophils populations present during the first 48 h post-infection, providing evidence about the existence of at least two predominant populations, where the larger is the one producing IL-10. Furthermore, we performed neutrophil transfer assays to C57BL/6 wild type (WT) and IL-10-/- mice (the latter highly susceptible to S. pneumoniae infection) to determine the role of IL-10–producing neutrophils during pneumococcal pneumonia. We transferred WT and IL-10-/- cells to each group and then we infected them with S. pneumoniae. A 10-days survival assay during was performed. Likewise, we evaluated lung infiltration of pro-inflammatory cells, as well as bacterial burden in lungs and other organs after 24 h post-infection. These results shown that transferred IL-10-/- mice were less susceptible to S. pneumoniae infection than untreated IL-10-/- mice. In contrast, we observed that WT mice transferred with WT cells showed an increased clinical score, decreased survival and a reduced bacterial clearance. Our results strongly suggest that neutrophils able to produce IL-10 might be modulating the lung immune response, playing a critical role during the first 48 h of S. pneumoniae infection.