Glycoprotein-adsorption from cancer sera--influence on a mixed lymphocyte culture

The nature of the inhibitory activity of sera of patients with metastatic cancer on in vitro immunoassays remains unclear. Serum glycoprotein levels in cancer patients show a reasonable correlation with the clinical status, especially with progressive metastatic disease. Glycoproteins like acute phase reactants have been connected with immunosuppressive activity in cancer patients' sera. In this study, we examined the influence of glycoprotein fractions of normal and cancer sera, separated by Con A immunoadsorption, on the mixed lymphocyte culture as a reference system for suppressive activity. Glycoprotein rich fractions with the utmost recovery of the acute phase reactants inhibited the mixed lymphocyte culture in a dose-dependent manner. This effect was more pronounced in patients sera as compared to control sera. But there is evidence of additional blocking activity in the glycoprotein poor serum fraction, indicating blocking factors still to be identified.