Datura lectin is both an anti-mitogen and a co-mitogen acting synergistically with phorbol ester

The lectins from Datura stramonium, Lycopersicon esculentum, and Solanum tuberosum are structurally related and possess a similar carbohydrate specificity, yet the Datura lectin is mitogenic for human lymphocytes while the other two are not. However, the Datura lectin was found to antagonize blast transformation induced by purified protein derivative (PPD), even within the concentration range at which it was optimally mitogenic on its own. The presence of a submitogenic concentration of the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA) enormously enhanced the mitogenic activity of Datura lectin. No such synergy was observed, however, between tomato lectin or S. tuberosum agglutinin (STA) and TPA, nor between Datura lectin and the calcium ionophore A 23187.