Role of L-alanine in the response of human lymphocytes to PHA and Con A.

The response of umbilical cord blood lymphocytes (UCBL) to PHA and Con A is strongly dependent upon the presence of dialyzable plasma components. The impaired response of human cells in the presence of dialyzed human plasma was restored by calf thymus extract. In the present experiments we have further purified calf thymus extract by means of paper electrophoresis and chromatography on thin-layer cellulose plates. We reached the conclusion that the active material in this model is a single amino acid, alanine. When the different isomeric forms of alanine were tested, we found that L-alanine is the only biologically active material. In addition, we have observed here that the allogeneic response of UCBL is also dependent upon the presence of dialyzable plasma components. This impaired allogeneic response of UCBL in the presence of DHP was restored by addition of L-alanine. The present findings suggest that, under in vitro conditions, for human cells to respond to mitogenic or allogeneic stimulation L-alanine is essential.