Relationship between amino-acid metabolism and immune functions in human lymphocytes

Amino-acid degradation, interleukin-2 (IL-2) production, and DNA synthesis were analysed in concanavalin A (ConA)-treated peripheral venous lymphocytes from healthy blood donors and in lymphocytes from patients after uneventful abdominal surgery. ConA augmented 14CO 2 production from (U- 14C) glutamine (492 ± 44 vs. 2274 ± 174 pmol/10 6 cells × 40 min −1) while it had little effect on 14CO 2 production from (1- 14C) leucine (132 ± 8 vs. 161 ± 17 pmol/10 6 cells × 40 min −1) compared with the respective controls. Similar effects on amino-acid degradation were observed in response to surgery. Glutamine but not leucine amplified IL-2 production from ConA-treated cells, and it was a prerequisite for DNA synthesis. In lymphocytes from operated patients, spontaneous incorporation of ( 3H) thymidine was higher on day 3 and day 6 (310 and 2660 cpm/10 6 cells) after surgery, compared with the pre-operative day (68 cpm/10 6 cells; median values). These results indicate 1) that glutamine is more critical than leucine for the immune function of T-lymphocytes, and 2) that lymphocytes from patients undergoing uneventful abdomional surgery have become stimulated in vivo. It is suggested that these cells may qualify as a suitable experimental model to study the metabolic basis for immunologic functions after antigenic stimulation in vivo.