During PRRSV infection, activated alveolar macrophages and other inflammatory cells secrete proinflammatory cytokines such as TNF-α, IL-1α/β, IL-6, IL-8, and IL-12, as well as TGF-β, to recruit neutrophils and lymphocytes to the site of infection and facilitate pathogen clearance [30, 31]. This evidence concerns the gene IL1A and infection.