Leptin increases T-cell immune response in birds.

Leptin is a 16 kDa protein hormone that besides being a satiety factor also functions as a pleiotropic molecule regulating endocrine and immune functions. The aim of this study was to investigate the role of leptin on mitogen stimulated T-lymphocyte proliferation in birds. In the first experiment (in vitro), peripheral blood was collected from turkeys and lymphocytes were isolated from samples. Recombinant chicken leptin was added at concentrations of 0, 10(-9), 10(-8), 10(-7), and 10(-6) M prior to mitogen stimulation with Concavalin A. BrdU incorporation allowed us to detect T-cell proliferation using intracellular labeling of nucleic acids. Mitogen activation induced with Concavalin A caused a proliferation of T-cells that was positively correlated with the concentration of leptin. In the second experiment (in vivo), asian blue quail were fitted with osmotic pumps releasing leptin and injected with phytohemagglutinin (PHA) in their wing-webs before, during, and after leptin administration. The response to mitogen was greater in leptin treated birds during the leptin administration, but not before or after. These findings demonstrate that leptin enhances mitogen stimulated T-cell proliferation in birds. The results correspond with previous reports on mammals.