L-Arginine regulates the expression of the T-cell receptor zeta chain (CD3zeta) in Jurkat cells.

L-Arginine is a versatile amino acid that plays a central role in the normal function of several organ systems including the immune system. Its availability is tightly controlled and varies significantly in different organs and tissues in the body. L-Arginine plays an important role in supporting T-cell proliferation. Its depletion in certain disease states results in a diminished T-cell response. The main purpose of this study was to determine the effect of the depletion of L-arginine on the expression of the T-cell receptor (TCR) proteins. When the helper T-cell line Jurkat was cultured in arginine-free medium, there was a preferential decrease in the expression of the TCR zeta chain (CD3zeta). The reduced expression of CD3zeta was observed within 24 h of culture in L-arginine-free medium and was completely reversed with the replenishment of L-arginine. Furthermore, the absence of L-arginine blocked the normal re-expression of the TCR that had been internalized after antigen stimulation. There also was a significant decrease in proliferation of Jurkat cells in the absence of L-arginine; however, L-arginine depletion did not prevent the up-regulation of the interleukin 2 receptor chains upon stimulation, nor did it significantly diminish the production of interleukin 2. The changes in the expression of CD3zeta chain were not induced by apoptosis. Thus, the availability of L-arginine in the microenvironment may play a significant role in regulating the expression of the TCR.