Prevalence of of alpha 1-antitrypsin Pi types among newborn infants of different ethnic backgrounds.

alpha 1-antitrypsin phenotypes were determined in cord sera of 1,010 healthy term infants of black, white and Hispanic background, by the crossed immunoelectrophoresis technique of Fagerhol and Laurell. Among the black group, M prevalence (97%) was higher than among the Hispanic group (88%). MS prevalance in the Hispanic group (6.7%) was higher than among black (1.5%) or white (3.9%) infants. Among those with an M pattern a "step" variant representing a shift of the relative amounts of protein in the major peaks of the M pattern, was found in 96% of neonates, but only among 9.8% of infants one months to two years of age and 18% among children two to ten years of age, regardless of race. Quantitative values of alpha 1-antitrypsin were not decreased among MS and MZ infants.