SEQUENTIAL PROLIFERATION INDUCED IN HUMAN PERIPHERAL-BLOOD LYMPHOCYTES BY MITOGEN .2. SUPPRESSION BY PHA-ACTIVATED CELLS

  • 1 January 1977
    • journal article
    • research article
    • Vol. 118  (5) , 1768-1773
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 50-60% as measured by 3H-TdR uptake and mitotic index. 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 TdR incorporation. Apparent suppression of proliferation by an extract of these cells was artifactual; the extract inhibited 3H-Tdr uptake but did not reduce mitotic activity. It is not known whether the inhibition exerted by the PHA-activated cells is mediated through a discrete subpopulation of suppressor cells or represents a regulatory function of any mitotic or post-mitotic cell, or both.