1.2 Major risk factors for meningitis Immature immunologic function and attenuated immunologic response to pathogens Low level of immunoglobulin defects of complement and properdin system Immature or impaired blood-brain-barrier(BBB) Immature BBB function maturation at about 1yr Impaired BBB: Congenial or acquired defects across mucocutaneous barrier1.2 Major risk factors for meningitis  Immature immunologic function and attenuated immunologic response to pathogens • Low level of immunoglobulin, defects of complement and properdin system  Immature or impaired blood-brain-barrier (BBB) • Immature BBB function: maturation at about 1yr • Impaired BBB: Congenial or acquired defects across mucocutaneous barrier