A postsynthetic modification of human α-fetoprotein controls its immunosuppressive potency

Abstract

In MATERIALS AND METHODSSerum (500 cm3) was obtained by plasmapheresis from patient Od, who had advanced hepatoma, 2 weeks prior to death. Ascitic fluid (2000 cm3) and tumor tissue (300 g) were obtained at autopsy. The tumor tissue was homogenized in 5 volumes of 10 mM phosphate-buffered 0.15 M NaCl (pH 7.4) and cleared of particulate matter by ultracentrifugation at 120,000 X g for 2 hr. Concentrations of a-fetoprotein in the serum, ascitic fluid, and tumor homogenate were 200, 150, and 50,gg/ml, respectively. From each of these three sources, a-fetoprotein was isolated by passage over an anti-a-fetoprotein immunoadsorbent column. Trace impurities were removed by subsequent passage over an anti-whole human serum immunoadsorbent column and Sephadex G-150, as described (1, 2). In addition, a-fetoprotein was isolated from a homogenate of fetal livers of 15-to 20-week-old stillborn human abortuses. All preparations of a-fetoprotein were pure as judged by immunoelectrophoresis and polyacrylamide gel electrophoresis (2). Lymphocyte transformation was assayed by triplicate cultures of 2 X 106 human peripheral blood lymphocytes in 1 ml of RPMI-1640 supplemented with 12.5% human heat-inactivated AB serum with addition of optimal doses of phytohemagglutinin (10 ytg/ml), concanavalin A (50 ,tg/ml), or antiserum against human thymocytes (25 'l/ml).

Characterization of human alpha fetoprotein charge microheterogeneity during fetal development

“…Although a physiological function of AFP is still uncertain, studies from the laboratory of Yachnin et al (Lester et al, , 1977(Lester et al, , 1978bYachnin and Lester, 1976) have demonstrated potent immunosuppressive effects of human AFP in fetal serum, fetal tissue extracts and ascitic fluid of hepatoma patients. The immunosuppressive activity was found to be several orders of magnitude higher in the fetus, with the most potent preparations isolated from fetuses at 10-20 weeks of gestation (a period of fetal development characterized by a preponderance of isoform 11).…”

“…The immunosuppressive activity was found to be several orders of magnitude higher in the fetus, with the most potent preparations isolated from fetuses at 10-20 weeks of gestation (a period of fetal development characterized by a preponderance of isoform 11). Furthermore, the most electronegative isoform of AFP identified by these investigators proved to be the most potent immunosuppresant (Lester et al, , 1977(Lester et al, , 1978b. No correlation was found between the carbohydrate content and the immunosuppupresant potency of the AFP isoform preparations, suggesting that some other charged moiety (fatty acids?)…”

Stimulatory Effect of Human Alpha‐Fetoprotein and its Molecular Variants on in‐Vitro‐induced Lymphocyte Blastogenesis

“…In our case, the source of AFP may change the proportions of variants. According to Lester et al [24], HAFP isolated from the serum and ascitic fluid of hepatoma-bearing patients and from fetal liver varied in biological potency by over three orders of magnitude. Furthermore, they demonstrated the existence of three molecular species of HAFP, and the quantitation of these three species revealed a correlation between the relative amount of the most electronegative species and immunosuppressive activity.…”

Attempts to Suppress Experimental Allergic Encephalomyelitis in Rats with Alpha Fetoprotein

“…Yachnin [8] found that the fetalderived human protein strongly inhibited the phytohemagglutinin-stimulated response of peripheral lymphocytes but AFP from the serum and ascites fluid of a hepatoma pa tient was less active. In other studies Lester et al [9] showed that AFP from fetal liver and from a hepatoma extract had over 100 times the activity of the protein isolated from the serum of the patient and approxi mately 500 times that isolated from the as cites fluid. Human AFP has been reported to suppress la-associated T cell proliferation in vitro [10].…”