A NEW FREQUENT ALLELE IS THE MISSING LINK IN THE STRUCTURAL POLYMORPHISM OF THE HUMAN MANNAN-BINDING PROTEIN

Human mannan-binding protein (MBP) is a serum lectin participating in the innate immune defence. Low MBP concentrations are explained by the dominant action of a point mutation at codon 54 of the MBP gene in Es kimos, partially in Caucasians, but not in Africans. A previously desc ribed point mutation at codon 57 was very frequent (0.23) in East Afri cans, low in Caucasians (0.02), and absent in Eskimos. The African pop ulation only conformed to Hardy-Weinberg expectation when assuming the existence of an unknown allele, which was subsequently found as a poi nt mutation at codon 52. This allele appeared with a relatively high f requency (0.05) in both Africans and Caucasians, but was absent in Esk imos. Hardy-Weinberg equilibrium is now seen in the investigated ethni c groups. All cases of MBP deficiency may be explained by these three variants.