Expansion of Human Lymphocyte Populations Expressing, Specific Immune Reactivities. II. A Comparison of Immune Reactivities in Human Tlymphocyte Lines Derived from Allogeneically Primed Cultures, Maintained with Lectins or Conditioned Medium

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Abstract
Lectins allow a strong expansion of in vitro primed cells. Among the lectins tested, PKW [pokeweed mitogen] but not PHA [phytohemagglutinin] or Con A [concanavalin A] reactivated CTL [cytotoxic T (thymus-derived) cells]. Whether a long term expansion of human T cells using iterative lectin stimulation could be maintained and (if so), whether the immune reactivities, once expressed in the original primed cells, could also be maintained was investigated. Lectins remain potent mitogens for primed cells, and allow good expansion over many cycles, provided fresh irradiated cells (autologous or not to the responder) are added to the cultures. When PKW is used as the iterative mitogen, both the specific proliferation (PLT; primed lymphocyte testing) and the specific cytotoxicity are maintained after each cycle. When PHA is the iterative stimulant, only the specific proliferation is maintained, while no measurable cytolysis is present. If iteratively PHA stimulated primed cells are cultured in the absence of PHA, even without additional specific stimulation, cytolytic activity is recovered from the cultures. In parallel, primed cells iteratively expanded using conditioned medium appear to retain both their specific lytic function and their specific proliferative function. Preliminary data suggest that the cloning efficiency when using lectins is higher than when using conditioned medium.