Immunochemical characterization of the suppressor factor from early human decidual cells.

Abstract

An immunosuppressive factor was obtained from culture supernatants of early human decidual cells. The suppressor factor was concentrated by gel filtration in a fraction with a molecular weight between 43,000 and 67,000 daltons. It was further purified by biochemical methods. Four peaks were obtained in the fraction with molecular weight between 43,000 and 67,000 daltons by anion exchange chromatography. Only the second peak had immunosuppressive activity in MLR. Lentil-lectin affinity chromatography of this suppressor factor showed that the suppressor factor had no affinity for lentil-lectin sepharose. Isoelectric focusing of the suppressor factor demonstrated four bands. The protein isoelectric (PI) point was approximately 7.50 in one band and between 6.85 and 7.35 in the other three bands. These results demonstrate that the suppressor factor is not glycoprotein but protein, whose PI is between 6.85 and 7.50. The suppressive effect of this purified factor on lymphokine production and lymphocyte activation was investigated. The addition of the purified suppressor factor to a culture of PBL stimulated with PHA suppressed not only IL-2 production and gamma-INF production, but also BSF-2 production. IL-2 receptor expression and transferrin receptor expression of PBL stimulated with PHA were also suppressed by addition of the suppressor factor. These results demonstrate that this suppressor factor inhibits lymphokine production and lymphocyte activation.