Isolation and partial characterization of plasma membranes bearing human fetal-associated antigens.

A rabbit antiserum to first-trimester human fetal tissue had greater reactivity in complement fixation and saturation binding assays with fetal tissues than with both a pool of normal adult lung, liver, and kidney and pools of the individual organs. This anti-fetal membrane reactivity was only partially inhibited by carcinoembryonic antigen. The serum still reacted strongly with human fetal and tumor cells after rendering it specific for plasma membrane components by adsorption to and elution from intact human fetal tissue culture cells. This plasma membrane-specific serum was then used to monitor the purification of the fetal membrane-associated antigens. The fetal antigens copurified with the putative plasma membrane enzymatic markers 5'-nucleotidase and Mg2+-adenosinetriphosphatase through differential and density gradient centrifugation. Insulin-binding activity only partially copurified with the antigenic activity. Little antigenic activity was found in nuclear and mitochondrial fractions. The isolation protocol gives fetal plasma membrane-associated antigens in approximately 50% yield with moderate purification. The sera and isolation procedures described should have general utility for the detection of human oncofetal antigens.

Electrophoretic and immunoelectrophoretic study of the enzymatic degradation of human orosomucoid (alpha 1 -acid glycoprotein).

Purified, intact orosomucoid (alpha 1-acid glycoprotein) derived from whole human plasma was incubated with a number of proteolytic and saccharolytic enzymes under a variety of conditions. The unfractionated digests were immediately examined by both agar gel- and immunoelectrophoresis for the presence of antigenically active (precipitating) and/or inactive macrofragments. Despite otherwise clear evidence of rapid degradation by several proteases, no antigenic subunits were detected. Among the glycosidases, almond emulsin produced a suggestion of modification of the carbohydrate moiety of a sialic acid-poor orosomucoid preparation obtained from Cohn Fr. VI, but had no effect on antigenic properties. These results are presented as further evidence for a lack of involvement of the extensive carbohydrate component of orosomucoid in its antigenic reactions, and support previous data implicating the polypeptide chain as solely responsible for its antigenicity.