SUMMARYThe aim of this study was to determine the developmental profile of mannose-binding protein (MBP) in preterm infants. MBP was measured in 885 longitudinally collected serum samples from 168 preterm infants, and 63 were genotyped with respect to the codon 54 mutation in the MBP gene. MBP level/codon 54 genotyping were also determined on the cord blood of 146/123 term infants and 138/123 adults, respectively. The best cut-off values of MBP for dividing preterm, term infants and adults into iow" and "high' M BP groups were 400 ng/ml (55 low, 113 high), 700 ng/ml (35 low, 111 high) and 750 ng/ml (33 low. 105 high), respectively, by achieving the least number of misclassifications according to the codon 54 mutation. The relative risk of the Mow" groups for presence of the codon 54 mutation compared with 'high" groups were 42 4, 67-9 and 22-9 for preterm, term infants and adults, respectively (PKO 00001). The gestational age and birth weight of the 'low* (n = 55) and 'high" (n= 113) MBP groups of the 168 preterm infants were 29 5 ± 2 8 weeks, 305±2-8 weeks (/'-003) and 1230±3I7g, I277±289g (/' = 035). respectively. The mean MBP levels of these two groups of preterm infants were different (P