A protective role for splenic neutrophils against Streptococcus pneumoniae infection (INC4P.338)

Abstract

Abstract The spleen is integral for protection against infections to encapsulated bacteria, such as S.pneumoniae. A recently identified splenic resident neutrophil subset has been proposed to contribute to this protection by modulating the antibody production of marginal zone B cells. To date, little is known regarding the function and behavior of these neutrophils in vivo and whether they actively contribute to protection against infection. Employing intravital microscopy we aimed to characterize splenic neutrophil behavior and function. Under basal conditions, two subsets of neutrophils are observed, a circulating phenotype and a resident phenotype. Infection with S. pneumonia stimulates a robust recruitment of neutrophils to the spleen and an enhanced localization within the marginal zone. This recruitment is accompanied by neutrophil activation typified by a reduction in cellular movement. Neutrophil depletion within the spleen during infection resulted in a reduction in bacterial clearance and a significant decrease in survival. Depletion of marginal zone B cells mimicked these parameters, suggesting both cell types contribute to a common protective mechanism. Our findings suggest that splenic neutrophils play a role in the protection against S. pneumoniae infection. Future studies will determine the contribution of resident vs recruited neutrophils to this protection and the role of these populations in mediating S.pneumoniae specific antibody production.