Cutting Edge: l-Arginine Transfer from Antigen-Presenting Cells Sustains CD4<sup>+</sup> T Cell Viability and Proliferation.
Metabolomics analyses suggest changes in amino acid abundance, particularly l- arginine (L-ARG), occur in patients with tuberculosis. Immune cells require L- ARG to fuel effector functions following infection. We have previously described an L-ARG synthesis pathway in immune cells; however, its role in APCs has yet to be uncovered. Using a coculture system with mycobacterial-specific CD4+ T cells, we show APC L-ARG synthesis supported T cell viability and proliferation, and activated T cells contained APC-derived L-ARG. We hypothesize that APCs supply L-ARG to support T cell activation under nutrient- limiting conditions. This work expands the current model of APC-T cell interactions and provides insight into the effects of nutrient availability in immune cells.