SIGLEC1 and susceptibility to pneumonia measurement: Recently we showed that intracellular replication of pneumococci in CD169+ tissue macrophages precedes invasive pneumococcal disease (IPD), in murine and porcine models, and that this could be prevented by macrolides, raising the hypothesis that an intracellular phase of bacterial replication could precede bacteraemic disease, but there was no evidence that this occurs during pneumonia or in the human spleen.