CHRONOLOGICAL CHANGES OF PROTEIN S IN NEWBORN AND INFANTILE PERIODS

Chronological changes of levels and plasma distribution of vitamin K-dependent protein S (PS) were studied in infants throughout the first 12 months of life. Total PS antigen (T-PS : Ag), C₄b-binding protein (C₄bp : Ag), free PS antigen (F-PS : Ag), PS : Ag complexed with C₄b-binding protein (C₄bp-S : Ag) and PS activity (PS : Act) were measured in 450 full term infants with no bleeding and thrombotic episodes. T-PS : Ag assayed by ELISA were 22.4±9.4 U/dl (mean±SD) on 0 day after birth (cord plasma), 22.3±9.4 U/dl on 1 day and rose gradually, reaching 72.0±16.8 U/dl at 12 months of age. PS : Act assayed by modified A-PTT using PS-immunodepleted plasma showed no increase but considerably higher levels in contrast with T-PS : Ag during the first 1 month of age, and then started to rise in parallel with T-PS : Ag, reachdsg 75.2±19.3 U/dl at 12 months of age. Although 54～57% (same as the normal adult value) of PS were found to be bound to C₄bp in infants after 3 months of age, only 11.9%～34.0% of PS were bound in infants before 1 month of age because of relatively lower levels of C₄bp