AGE-DEPENDENT VARIATION IN THE SERUM CONCENTRATION OF MANNAN-BINDING PROTEIN

Mannan-binding protein (MBP) is an acute phase reactant, and its defic iency:is associated with the common opsonic defect and suspectibility to infections and atopic constitution. The aim of this study was to in vestigate the changes occurring in the serum level of MBP in infancy a nd during later childhood. We studied the serum concentration of MBP i n 611 Finnish children of different ages and 110 adults by using an en zyme immunoassay. In an analysis of successive serum samples from infa nts at the day of birth and at the ages of 1 and 5 months, and at 1 an d 2 years, the serum concentration of MBP increased significantly afte r birth, and was at its highest (the mean and median were 8.13 and 8.4 9 mg l(-1), respectively) at the age oi 1 month. After that, it declin ed to the initial level until the age of 5 months. The MBP concentrati on continued to decrease during childhood, and after the age of 12 yea rs the MBP values reached the adult level. In Finnish adults the mean and median concentrations of MBP were 4.48 and 4.02 mg l(-1), respecti vely, which seem to be higher than those reported previously in other populations. The high concentration of MBP in infants may best be expl ained by exposure to novel environmental antigens in early childhood, which suggests a protective roll: for MBP during the period of immatur ity of the immunosystem. In older children the high level of MBP can p robably be explained by childhood infections and the ensuing need of M BP.