Purification and characterisation of an immunosuppressive factor from normal human seminal plasma

We have previously described the presence of a human seminal plasma component which may prevent the immunologic sensitization of females against sperm and seminal plasma antigens. Purification of the immunosuppressive factor (ISF) by saturated ammonium sulphate precipitation, followed by Sepharose 4-B column chromatography and Con-A Sepharose 4-B affinity chromatography is described here. An apparently single-band protein on SDS gel electrophoresis, having a molecular weight of 35,000, has been isolated. Amino acid analysis of this glycoprotein shows that it is rich in isoleucine, glycine, glutamine and proline, while methionine, tyrosine and asparagine are present in traces.