Differential impact of l-arginine deprivation on the activation and effector functions of T cells and macrophages

The metabolism of the amino acid l-arginine is emerging as a crucial mechanism for the regulation of immune responses. Here, we characterized the impact of l-arginine deprivation on T cell and macrophage (MΦ) effector functions: We show that whereas l-arginine is required unconditionally for T cell activation, MΦ can up-regulate activation markers and produce cytokines and chemokines in the absence of l-arginine. Furthermore, we show that l-arginine deprivation does not affect the capacity of activated MΦ to up-regulate l-arginine-metabolizing enzymes such as inducible NO synthase and arginase 1. Thus, our results show that to exert their effector functions, T cells and MΦ have different requirements for l-arginine.