IL2 and schizophrenia: One hypothesis was based on the macrophage-T lymphocyte theory, according to which cytokines such as interleukin-1 (IL-1), IL-2, tumor necrosis factor-α (TNF-α), interferon-α (IFN-α), and IFN-γ that are produced by chronically activated macrophages and T lymphocytes, are the key mediators of schizophrenia (18).