As children age, they become less susceptible to the diverse microbes causing pneumonia.
These microbes are pathobionts that infect the respiratory tract multiple times during
childhood, generating immunological memory. To elucidate mechanisms of such naturally
acquired immune protection against pneumonia, we modeled a relevant immunological
history in mice by infecting their airways with mismatched serotypes of Streptococcus
pneumoniae (pneumococcus). Previous pneumococcal infections provided protection …