title: Sequential proliferation induced in human peripheral blood lymphocytes by mitogen. II. Suppression by PHA-activated cells.
abstract: Human peripheral blood cells from cultures stimulated by phytohemagglutinin (PHA) for 3 days suppressed continued proliferation when added to feeder layer cultures of autologous lymphocytes previously stimulated with mitogen. Proliferation 1 day after the addition of inhibitory cells was reduced 50 to 60% as measured by tritiated thymidine (3HTdR) uptake and mitotic index. It is suggested that a similar suppressive phenomenon may be acting in most standard mitogen-stimulated cultures to limit cell division after only a few days of culture. Suppression of continued lymphocyte proliferation in the feeder layer cultures by cells from PHA-stimulated cultures was not due to cell crowding, carry-over of mitogen, or nutrient depletion; nor was it an artifact of thymidine incorporation. Apparent suppression of proliferation by an extract of these cells, however, was artifactual; the extract inhibited 3HTdR uptake but did not reduce mitotic activity. It is not known whether the inhibition exerted by the PHA-activated cells is mediate through a discrete subpopulation of "suppressor cells" or represents a regulatory function of any mitotic or post-mitotic cell, or both.
mesh_terms: D002455:Cell Division; D002478:Cells, Cultured; D006801:Humans; D007165:Immunosuppression Therapy; D037102:Lectins / Q000494:pharmacology*; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000276:immunology / Q000378:metabolism; D008937:Mitomycins / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism; D013997:Time Factors
chemical_list: D037102:Lectins; D008937:Mitomycins; D013936:Thymidine