Innate immune responses to Streptococcus pyogenes

This Report summarizes the work of a ERA-Net Pathogenomics call that was carried out in collaboration with five European partners. Our part focused on the study of important host factors in the response to pneumococcal infection.Pneumonia caused by S. pneumoniae is one of the most prevalent and potentially life threatening infections worldwide. In this project we investigated the role of certain macrophage receptors and secreted mediators in the host defense against pneumococci. To this end we discovered and analyzed in detail the biological function of a receptor expressed on lung macrophages and could show that this receptor importantly contributes to the phagocytosis and clearance of bacteria from the lungs. In another part of this project we discovered that macrophages released of a small protein that itself alters the functional properties of these cells, as it deactivates macrophages. This protein thereby impaired outcome from bacterial pneumonia. Importantly so, we also discovered the presence of this protein in lung samples from patients suffering from pneumonia, hence indicating that this molecule might serve as a marker to identify patients with inappropriate immune responses to bacteria.