 This randomized clinical trial will study immune function in healthy volunteers given short-term 4 week treatment with either sitagliptin or placebo. During the study, we will take blood samples at various time intervals before, during and after treatment. We will compare the immune response with and without sitagliptin treatment using blood samples from healthy individuals. We will measure changes in the magnitude and type of immune responses. The study period is nine weeks. The study s primary outcome will be changes in blood plasma levels of a protein marker associated with decreased inflammation: Transforming Growth Factor-Beta1 TGFb1. In addition, we plan to use these blood samples to measure sitagliptin s effect on expression levels of several cytokines immune proteins. We will also measure the level of proliferation in stimulated PBMCs blood immune cells and gene expression in whole blood after sitagliptin treatment. 