CMV is one of the most important opportunistic infection in transplant recipients. In South Korea, more than 95% of adults reveal sero-positivity for CMV IgG. Until now, sero-positivity for CMV IgG before solid organ transplantation is a laboratory test of choice to stratify the risk of CMV reactivation after solid organ transplantation. Theoretically, CMV-specific cell-mediate immune response before solid organ transplantation will further categorize the patients into high or low risk of CMV development after solid organ transplantation. The investigators thus evaluate the usefulness of CMV-specific ELISPOT assay in kidney transplant candidates to predict the development of CMV infection after kidney transplantation.