Inhibitors of dipeptidylpeptidase IV (DPP-IV) represent a novel class of 
frequently used anti-diabetic drugs. In addition to its function in metabolic 
regulation, DPP-IV also plays a role in the immune system. Whether the DPP-IV 
inhibitors sitagliptin, vildagliptin or saxagliptin impair immune responses is, 
however, currently unknown. Here, we investigated the effect of these agents on 
both innate and adaptive immunity. We found that the DPP-IV inhibitors did not 
affect the innate immune response induced by Toll-like receptor (TLR) ligands, 
as cytokine secretion and induction of co-stimulatory molecules by human blood 
mononuclear cells was not impaired. Furthermore, proliferation of T cells and 
suppressive function of regulatory T cells was preserved. Mice treated with 
vildagliptin showed normal cytokine production, immune cell activation and 
lymphocyte trafficking upon TLR activation. Thus, crucial immunological 
parameters remain unaffected upon treatment with DPP-IV inhibitors, a fact that 
is reassuring with respect to safety of these drugs.