Alpha-1-antitrypsin concentration in human milk

Alpha-1-antitrypsin concentration was analyzed by immunoelectrophoresis in samples of human colostrum (n = 3) and of mature milk from mothers between 2 to 52 wk postpartum (n = 39), one of whom was known to be PiMZ with a PiZZ infant. All milk samples tested contained alpha-1-antitrypsin. The three colostrum samples contained 140, 520, and 250 mg/liter. The mature milk of women who had been lactating less than 6 months had a higher concentration (7.2 +/- 3.6 mg/liter) (mean +/- SD) than in the women who had been lactating 6-12 months (4.8 +/- 1.8 mg/liter) (p less than 0.03). The milk of the woman of Pi type MZ had an alpha-1-antitrypsin concentration of 7.0 mg/liter at 7 wk postpartum and 4.1 mg/liter at 52 wk. It has been previously demonstrated that enhanced absorption of intact proteins occurs in early infancy. The presence of antiproteases in human milk provided during early infancy may serve to inhibit the absorption of intact proteases, limiting their entry into the portal circulation.