title: A human soluble suppressor factor affecting lymphocyte responses in vitro.
abstract: A soluble suppressor factor (SSF) has been demonstrated in the supernatant of normal human peripheral blood lymphocyte cultures that exhibits suppressive activity toward the proliferative response of normal lymphocytes to concanavalin A or alloantigens in mixed lymphocyte culture (MLC) or toward pokeweed mitogen-stimulated immunoglobulin synthesis and secretion in vitro. Suppression of the proliferative response in MLC reached maximal levels when added SSF-containing supernatant approximated 20% by volume of the culture medium. Suppression in the MLC was found to act at the proliferative stage. SSF acts independently of cytotoxicity and is stable at 56 degrees C for 30 min but is inactivated at higher temperatures. Addition of SSF to the MLC as late as day 4 after initiation of the culture results in suppression of transformation. This factor(s) may regulate the magnitude of several immune responses in humans.
mesh_terms: D000917:Antibody Formation / Q000187:drug effects; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D006801:Humans; D007108:Immune Tolerance; D008213:Lymphocyte Activation / Q000187:drug effects; D007959:Lymphocyte Culture Test, Mixed; D008214:Lymphocytes / Q000276:immunology*; D008222:Lymphokines / Q000494:pharmacology*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
chemical_list: D008222:Lymphokines