[Immunosuppressive factor(s) present in crude preparations of human chorionic gonadotropin]

The present study was undertaken to purify and characterize the immunosuppressive factor(s) present in commercially available crude human chorionic gonadotropin (crude hCG). Amberlite CG-50 column chromatography of crude hCG(2,680 IU/mg) produced hCG(7,130 IU/mg) and non hCG(130 IU/mg) fractions. The hCG fraction was further fractionated by Sephadex G-100 column chromatography and a highly purified fraction with a potency of 18,600 IU/mg was obtained. The non hCG fraction was separated into two fractions, F-1 and F-2, on Sephadex G-75. Each fraction was examined for its inhibitory effect on the incorporation of 3H-thymidine by normal human peripheral blood mononuclear cells stimulated with phytohemagglutinin (PHA test) or mixed lymphocyte reaction (MLR test). The original crude hCG showed considerable inhibition in both PHA and MLR tests, but the purified hCG showed no inhibition. F-1 fraction, having a molecular weight (M.W.) ranging from 75,000 to 100,000 daltons, was the most potent in the inhibition of all the other fractions. The inhibitory activity in the F-1 fraction was dose-dependent and relatively stable when exposed to heat and trypsin treatment, but completely inactivated by neuraminidase treatment. These results strongly suggest that the macromolecular substance(s), with a M.W. of 75,000 to 100,000, which is present in crude hCG but different from genuine hCG, has potent immunosuppressive effects and that sialic acid residues in the substance(s) are related to the manifestation of these effects.