CCL2 and autism spectrum disorder: Epidemiologic studies have also indicated other immune risk factors during early gestation, such as significantly increased levels of interferon-γ (IFN-γ), interleukin-4 (IL-4), interleukin-5 (IL-5), tumor necrosis factor-α (TNF-α), tumor necrosis factor-β (TNF-β), increased interleukin-10 (IL-10) and increased amniotic fluid levels of monocyte chemotactic protein-1 (MCP-1) in autism spectrum disorders [39,40].