title: Spontaneous production of a suppressor factor by the human macrophage-like cell line U937. I. Suppression of interleukin 1, interleukin 2, and mitogen-induced blastogenesis in mouse thymocytes.
abstract: The human macrophage-like cell line U937 spontaneously produced a nondialyzable factor that inhibited interleukin 1 (IL 1), interleukin 2 (IL 2), and phytohemagglutinin (PHA)-induced blastogenesis in mouse thymocytes. The suppression by U937 supernatant factor occurred independently of the concentration of IL 1 or PHA, indicating that it was noncompetitive. The U937 suppressor factor was not cytotoxic for thymocytes, nor did it affect the spontaneous proliferation of T lymphoblastoid cell lines and U937. Physicochemical characterization showed that the U937 suppressor factor was nondialyzable, partially inactivated by heat treatment (56 degrees C), ammonium sulfate (67% saturation) precipitable, sensitive to pH 2.5, and resistant to freeze-thawing. Molecular weight of the factor inhibiting co-mitogenic IL 1 activity was approximately 85,000, as estimated by gel filtration. The U937 cell line may provide a model for the study of mechanisms and mediators of immunosuppression by mononuclear phagocytes.
mesh_terms: D000818:Animals; D002460:Cell Line; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D006801:Humans; D007166:Immunosuppressive Agents / Q000096:biosynthesis* / Q000502:physiology; D007375:Interleukin-1 / Q000502:physiology; D007376:Interleukin-2 / Q000502:physiology; D008213:Lymphocyte Activation; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D015846:Monokines; D010835:Phytohemagglutinins / Q000494:pharmacology; D014176:Protein Biosynthesis; D011506:Proteins / Q000032:analysis / Q000502:physiology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D007166:Immunosuppressive Agents; D007375:Interleukin-1; D007376:Interleukin-2; D015846:Monokines; D010835:Phytohemagglutinins; D011506:Proteins