IL-2 is produced by CD3ζ+ CD57− CD8+ T cells.

Normal donor PBMC and convalescent samples from donors AI-1 (day 54) and AI-2 (day 100) were activated overnight with anti-CD3 and PMA in the presence of Brefeldin A before staining for intracellular IL-2. Each sample was analyzed for cytokine production by gated CD8+ lymphocytes. Cytokine production without T-cell activation was less than 1% in all samples (data not shown).