Modulation of human lymphocyte proliferation by amino acids.

The amino acids required for phytohaemagglutinin (PHA) induced lymphocyte proliferation were determined by the 3H-thymidine incorporation in amino acid-deficient media. Results indicate that the PHA-stimulated lymphocytes require alanine and serine in addition to 13 other amino acids present in Eagle's minimal essential medium (arginine, cysteine, glutamine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, tyrosine, and valine). The omission of any one of the 13 amino acids would stop almost completely the proliferation of PHA-stimulated lymphocytes. The omission of serine from RPMI 1640 medium caused a mean reduction of 64% of cell proliferation, while the addition of alanine to PRMI 1640 culture medium caused a mean increment of 52%. The lymphocyte proliferation appears to be modulated by amino acids in the culture medium, and for optimal growth of lymphocytes, all these 15 amino acids are essential.