The hypertriglyceridemia of infection is mediated by many of the cytokines that regulate the immune response, including the tumor necrosis factors, the interleukins and the interferons. In the acquired immunodeficiency syndrome (AIDS), hypertriglyceridemia is most likely due to increased circulating levels of interferon alpha. Both in AIDS and in animal models there is no direct association between the presence of hypertriglyceridemia and the syndrome of wasting. Rather, circulating lipoproteins may neutralize infectious organisms and therefore contribute to host defense.