Serum a - Fetoprotein , Albumin , and yG - Globulin in the Human Conceptus

The serum of the human fetus contains a protein that is not present in the sera of normal children or adults (1, 2). This protein has been observed in the serum of the conceptus as early as 10 to 14 weeks in the gestational period, and it has been reported that the serum concentration of the protein decreases as gestation continues (1-7). Most investigators have been unable to detect the protein in fetuses older than 4 to 6 months' gestation (1-6, 8) or in prematurely born infants (5), but others have reported its presence in cord serum and in the serum of the newborn during the first week of life (9, 10). The electrophoretic mobility of this serum fetoprotein at pH 8.6 is that of an a-globulin, the protein migrating somewhat slower than serum albumin but faster than the serum a1-globulins at this pH (1-10). As is well known, fetal calf serum also contains an a-globulin, the mucoprotein fetuin (11), which is not found in adult bovine serum. Calf fetuin, however, has a molecular weight of approximately 45,000 (12) and contains galactose, whereas human serum a-fetoprotein appears to have a molecular weight similar to that of serum albumin, 65,000, and is galactose free (24). Bodman (8) has suggested that serum a-fetoprotein present in the human fetus of less than 4 months' gestation is actually fetuin without galactose, and he has reported that after 4 months' gestation, the a-fetoprotein acquires galactose and can react with antisera prepared againstcalf fetuin. On the other hand, de Muralt and Roulet (5) were unable to obtain a precipitin reaction between human