Human alpha-fetoprotein-rich fraction inhibits galactocerebroside antibody-mediated lysis of oligodendrocytes in vitro.

Polyclonal rabbit antiserum to galactocerebroside (anti-GalC) produces titer-dependent lysis of cultured Percoll-isolated bovine and rat oligodendrocytes. In this study anti-GalC produced complement-dependent lysis of 76% of the bovine cells and 65% of the rat cells maintained for 3 to 6 days in vitro. With the concomitant addition of human umbilical cord serum fractions containing fetal alpha-fetoprotein (AFP), lysis was decreased to 31% and 39%, respectively. Control antisera (anti-complete Freund's adjuvant/albumin) showed a cytotoxicity index of 15% for bovine cells and 23% for rat cells. Neither albumin, nor normal human serum, nor any of several pregnancy-associated hormones reduced the lysis produced by anti-GalC. AFP-rich fraction reduced oligodendrocyte lysis when mixed with anti-GalC or complement, but not when first incubated with the cells. Similar findings were obtained when AFP was assayed in specific oligodendrocyte radioimmunoassays utilizing anti-GalC antibody. Our experiments indicate that AFP activity may result from its binding to anti-GalC antibody; it is possible that the Fc portion of the antibody is involved. These data provide in vitro evidence of a possible immunosuppressive role of AFP in the central nervous system.