Colonization-induced protection against invasive pneumococcal disease in mice is independent of CD103 driven adaptive immune responses.

Nasopharyngeal colonization with Streptococcus pneumoniae (the pneumococcus) is known to mount protective adaptive immune responses in rodents and humans. However, the cellular response of the nasopharyngeal compartment to pneumococcal colonization and its importance for the ensuing adaptive immune response is only partially defined. Here we show that nasopharyngeal colonization with S. pneumoniae triggered substantial expansion of both integrin αE (CD103) positive dendritic cells (DC) and T lymphocytes in nasopharynx, nasal-associated lymphoid tissue (NALT) and cervical lymph nodes (CLN) of WT mice. However, nasopharyngeal de-colonization and pneumococcus-specific antibody responses were similar between WT and CD103 KO mice or Batf3 KO mice. Also, naïve WT mice passively immunized with antiserum from previously colonized WT and CD103 KO mice were similarly protected against invasive pneumococcal disease (IPD). In summary, the data show that CD103 is dispensable for pneumococcal colonization-induced adaptive immune responses in mice.