Chemical characterization and immunological analysis of the suppressor factor from human decidual cells

Abstract

To determine the chemical characteristic of the immunosuppressive factor in the culture supernatants from decidual cells, serial biochemical methods were applied. The suppressor factor was obtained in the fraction with a molecular weight between 43,000 and 67,000 after a gel filtration of the supernatants, and showed four major peaks on an anion exchange chromatography. Of the four peaks, only the second peak with an ion strength of 0.3 M had immunosuppressive activity on mixed lymphocyte reaction (MLR). The following study on a Lentil-Lectin affinity chromatography showed that the suppressor factor had no affinity to Lentil-Lectin. An isoelectric focusing of the purified suppressor factor showed four bands, protein isoelectric point (PI) of which was between 6.85 and 7.50. To elucidate how the suppressor factor mediate an immunosuppressive activity, effects of the suppressor factor on lymphokine production and lymphocyte activation of periferal blood lymphocytes (PBL) stimulated with 0.05% PHA were investigated. The purified suppressor factor inhibited not only lymphokine production (IL-2: 61.2% inhibition, γ-IFN: 32.6% inhibition, BSF-2: 33.1%) of PBL, but also the expression of activated surface markers on lymphocytes (IL-2 receptor: 33.8%, transferrin receptor: 33.7% inhibition) at a concentration of 5 μg/ml. These results clearly demonstrate that the suppressor factor from human decidual cells, which is protein but not glycoprotein and PI of which is between 6.85 and 7.50, mediate a nonspecific immunosuppressive activity by inhibiting lymphokine production and lymphocyte activation. © 1989, The Japan Society for Clinical Immunology. All rights reserved.