Considered for a long time merely as an inert tissue exclusively devoted to energy storage, white adipose tissue is currently viewed as a very active secretory organ, participating in the regulation of several physiological and pathological processes, including immunity and inflammation. Adipocytes and other cells associated with adipose tissue produce and release a dazzling variety of immunomodulatory and pro- and anti-inflammatory factors, including the adipokines leptin, adiponectin, visfatin, and resistin as well as cytokines, chemokines and other mediators. Similarities between adipocytes and macrophages, as well as cross-talk between adipocytes and immune cells, make adipose tissue a direct contributor in coordinating the immune and inflammatory response. In contrast, reduced adiposity predisposes to increased susceptibility to infection in malnourished individuals. Finally, altered systemic or local levels of adipose-derived factors are observed in a variety of inflammatory and autoimmune conditions such as obesity, type 2 diabetes mellitus, atherosclerosis, asthma, rheumatoid arthritis, inflammatory bowel disease, and multiple sclerosis. Thus, adipose tissue acts as an active coordinator of body homeostasis, in part by modulating activation of the immune-inflammatory system.