We here investigated the role of Btk in the innate host defense against S. pneumoniae using well established models of pneumonia and sepsis (14, 25) in Btk deficient (Btk-/-) mice, Btk-/- mice in which Btk expression is exclusively restored in B cells or in MhcII+ cells by a Btk transgene and in mice with a targeted deletion of the Btk gene specifically in myeloid cells (Table S1). The gene discussed is BTK; the disease is pneumonia.