Fecal microbiota transplantation (FMT) experiments in mice with Streptococcus pneumoniae infection depleted of gut microbiome detected normalization of lung bacterial counts and tumor necrosis factor-α and interleukin-10 levels, indicating that the gut microbiome plays a role in protecting the host during Streptococcus pneumoniae infection (32). Here, IL10 is linked to pneumococcal infection.