Leptin, an adipose-secreted hormone, links metabolism and immunity. Our aim was 
to determine whether leptin affects the alloimmune response. We used an 
allogeneic skin transplant model as a means to analyze the allograft immune 
response in Lep(ob/ob) and wild-type mice. Leptin deficiency results in an 
increased frequency of Treg and Th2 cells and a prolonged graft survival. These 
effects of leptin deficiency indicate the importance of leptin and obesity in 
modulating the allograft immune responses. Our data suggest a possible 
explanation for the increased susceptibility of hyperleptinemic obese patients 
to acute and chronic graft rejection.