Abstract
Summary
The nonspecific mitogen, phytohemagglutinin (PHA) did not induce increased cell proliferation in guinea pig bone marrow cell cultures. PHA was demonstrated to be a potent stimulus for lymph node cell replication. Unstimulated marrow cultures showed a high rate of 3HTdr incorporation, activity attributed primarily to hematopoiesis. This activity was not increased following PHA stimulation. Guinea pig bone marrow contained approximately 40% lymphoid cells; thus, failure to demonstrate a response could not be attributed to a deficiency of these cells. Furthermore, in mixed lymph node-bone marrow cell cultures, the addition of responsive lymphocytes resulted in measurable augmentation of isotope incorporation. These results are consistent with concepts regarding the heterogeneity of lymphoid populations; the majority of marrow lymphocytes appear to be unresponsive to this stimulus of in vitro peripheral lymphopoiesis.
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