Leptin is an adipokine which conveys information on energy availability. In humans, leptin
influences energy homeostasis and regulates neuroendocrine function primarily in states of
energy deficiency. As a cytokine, leptin also affects thymic homeostasis and, similar to other
proinflammatory cytokines, leptin promotes Th1 cell differentiation and cytokine production.
We review herein recent advances on the role of leptin in the pathophysiology of immune
responses.