L-Arginine modulates CD3zeta expression and T cell function in activated human T lymphocytes.

Engagement of the T cell receptor (TCR) by antigen or anti-CD3 antibody results in a cycle of internalization and re-expression of the CD3zeta. Following internalization, CD3zeta is degraded and replaced by newly synthesized CD3zeta on the cell surface. Here, we provide evidence that availability of the amino acid L-arginine modulates the cycle of internalization and re-expression of CD3zeta and cause T cell dysfunction. T cells stimulated and cultured in presence of L-arginine, undergo the normal cycle of internalization and re-expression of CD3zeta. In contrast, T cells stimulated and cultured in absence of L-arginine, present a sustained down-regulation of CD3zeta preventing the normal expression of the TCR, exhibit a decreased proliferation, and a significantly diminished production of IFNgamma, IL5, and IL10, but not IL2. The replenishment of L-arginine recovers the expression of CD3zeta. The decreased expression of CD3zeta is not caused by a decreased CD3zeta mRNA, an increased CD3zeta degradation or T cell apoptosis.