IL4 and Autoimmunity: TH2 cells predominantly secrete IL-4 and stimulate the proliferation of B cells and production of antibodies; TH17 cells produce proinflammatory cytokine IL-17 and play a major role in autoimmunity; Treg and those with a regulatory function, in contrast, are important for the control of immune responses to self-antigens, preventing autoimmunity and maintaining self-tolerance.