Metal Cation Requirements for Phytohemagglutinin-Induced Transformation of Human Peripheral Blood Lymphocytes

Citrate and disodium EDTA were effective inhibitors of PHA-induced lymphocyte transformation. A high concentration of citrate (24 mM) was required. Citrate inhibition was totally reversible by calcium and half as effectively by magnesium. In experiments in calcium-magnesium-free medium, calcium was determined to be five times as effective as magnesium in promoting transformation. EDTA was effective in low concentrations (1.6 mM) in blocking transformation. This effect was not entirely reversible by calcium, and was not detectably affected by magnesium. Several other metal cations were effective in reversing EDTA inhibition of PHA-induced transformation. Zinc and iron appear likely to be essential for PHA-induced lymphocyte transformation in vitro.