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

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• T cell receptor (TCR) engagement triggers a cycle of CD3zeta internalization and re-expression.
• CD3zeta is essential for TCR signaling and T cell activation.
• The role of amino acid availability in regulating this cycle and T cell function is not fully understood.

Purpose of the Study:

• To investigate the effect of L-arginine availability on the CD3zeta cycle and T cell function.
• To determine if L-arginine deficiency causes T cell dysfunction.

Main Methods:

• T cells were stimulated and cultured with or without L-arginine.
• CD3zeta expression, TCR surface levels, T cell proliferation, and cytokine production (IFNgamma, IL5, IL10, IL2) were analyzed.
• Mechanisms like mRNA levels, protein degradation, and apoptosis were assessed.

Main Results:

• T cells cultured without L-arginine showed sustained CD3zeta down-regulation, impaired TCR expression, and decreased proliferation.
• Production of IFNgamma, IL5, and IL10 was significantly diminished in L-arginine-deficient T cells, while IL2 production remained unaffected.
• Replenishment of L-arginine restored CD3zeta expression.
• Decreased CD3zeta expression was not due to reduced mRNA, increased degradation, or apoptosis.

Conclusions:

• L-arginine availability is a critical modulator of the CD3zeta expression cycle and T cell function.
• L-arginine deficiency induces T cell dysfunction through sustained CD3zeta down-regulation.
• These findings highlight the importance of L-arginine in maintaining T cell responsiveness.