Until now, the detailed dynamic of sIL-7R and IL-7 interaction in ex vivo collected clinical material has not been determined, yet a biologically and clinically relevant time frame to test for sIL-7R would be monthly within the first three month after HSCT; a time frame with a high risk to develop CMV infection and/or GVHD. The gene discussed is IL7; the disease is cytomegalovirus infection.