Effect of leukoagglutinating phytohemagglutinin on cAMP and cGMP levels in lymphocytes

In concentrations which do not affect the cellular concentrations of the cyclic nucleotides cAMP and cGMP, phytohemagglutinin (PHA) (crystalline, kidney-bean leukoagglutinin) can activate adenoidal lymphocytes. High concentrations of leukoagglutinin caused an increase in cAMP without stimulating mitosis in lymphocytes. Our results do not support the concept that cyclic nucleotides act as mediators for lymphocyte activation by lectins. Previous contradictory reports on the role of cyclic nucleotides may have been due to the use of impure bean extracts and lymphocytes.