Phytohemagglutinin (PHA-M), the major seed lectin of the common bean, Phaseolus vulgaris, accumulates in the parenchyma cells of the cotyledons. Phytohemagglutinin is a T-cell activator. Stimulation of human mononuclear leukocytes by Phytohemagglutinin induces the expression of ChAT mRNA, and potentiated ACh synthesis.