TNF and autoimmune disease: TNF-α is a cytokine produced by macrophages; IL-1 plays a central role in the regulation of the immune and inflammatory responses; IL-2 has essential roles in key functions of the immune system, primarily via its direct effects on T cells; IFN-γ is closely associated with a number of autoinflammatory and autoimmune diseases; in the plasma of rats, expression levels of IL-1β and TNF-α remarkably increase when treated by Pb [31]; in the bursa of fabricius of the chickens, Pb treatment significantly decreased the expression levels of IL-2 and IFN-γ [32].