 Adipose tissue plays an important role in the body's metabolism and energy homeostasis. It also produces the hormone leptin, which regulates the immune system and can affect susceptibility to infections or autoimmunity. Conditions of reduced leptin production are linked to increased infection susceptibility, while conditions of excessive leptin production are associated with increased production of pro-inflammatory cytokines and other pathogenic factors. This article was authored by Patricia Fernandez-Riejoz, Saoud Najib, Jose Santos-Alvarez, and others.