title: Supernatant derived from a human hepatocellular carcinoma cell line (PLC/PRF/5) activates a population of T-suppressor cells.
abstract: Harvest fluid derived from a primary hepatocellular carcinoma cell line (PLC/PRF/5) inhibited the incorporation of 3H-thymidine into PHA-activated human lymphocytes. A similar effect was observed when lymphocytes were pre-incubated with the tumour supernatant and washed prior to mitogen activation. Not only did the tumour supernatant inhibit 3H-thymidine incorporation by mitogen-activated lymphocytes, but it also inhibited production of the lymphokine leucocyte inhibitory factor (LIF). In experiments designed to establish whether a component of the tumour harvest fluid was activating a population of suppressor cells, normal mononuclear (MN) cells were treated with the PLC/PRF/5 or embryonic fibroblast supernatant for 48 h, after which they were washed and added to normal mitogen-activated lymphocyte cultures. Only cells pretreated with the PLC/PRF/5 supernatant suppressed mitogenesis. The cell responsible for the suppressor effect was a T cell, which after a further 24 h in culture liberated a suppressor factor responsible for inhibiting lymphocyte function. Although the nature of the factor/s in the PLC/PRF/5 supernatant responsible for activation of the T-suppressor cell population is unknown, it is suggested that this mechanism may be important in protecting the tumour from the immune response.
mesh_terms: D000818:Animals; D001402:B-Lymphocytes; D002460:Cell Line; D005110:Extracellular Space / Q000276:immunology; D006801:Humans; D008114:Liver Neoplasms, Experimental / Q000276:immunology*; D008213:Lymphocyte Activation; D008222:Lymphokines / Q000096:biosynthesis; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
chemical_list: D008222:Lymphokines; C010598:leukocyte inhibitory factor