CD8+ memory T cells metabolize ammonia into urea and citrulline through cytosolic arginine via the urea and citrulline cycles, which supports their long-term survival and memory development under laboratory conditions.

CD8+ memory T cells remove toxic ammonia by converting it into urea and citrulline using two connected biochemical pathways. First, ammonia combines with other molecules to form a compound that builds arginine in the cell's main fluid. This arginine is then split in two directions: one part goes into the cell's energy factory to make urea, and another part stays in the main fluid to make citrulline. Removing ammonia this way allows the cells to survive longer and become long-lasting memory cells.