Human Mannose-binding Lectin in Immunity : Friend, Foe, or Both?

Human mannose-binding lectin (MBL) recognizes a wide range of microorganisms and triggers the most ancient pathway of complement activation. However, ∼5% of individuals lack functional serum MBL and have not been found to be prone to severe infections in prospective studies. These data suggest that human MBL is largely redundant for protective immunity and may even have been subject to counter selection because of a deleterious impact.