 The purpose of this study is to extend previous observations in animal models regarding the effects of adenosine in the release of cytokines to human subjects. We intend to accomplish this in two study protocols. In the first we will infuse intravenously adenosine and measure the plasma levels of inflammatory cytokines. In the second one, we will use a microdialysis technique to infuse intradermally small amounts of adenosine and will measure skin blood flow and will take a biopsy to measure levels of mRNA for cytokines. 