Different parameters (CD4+ count, different cytokines and chemokines, presence of tumors and opportunistic infections, GVHD, presence of other viruses, acute and chronic graft rejection, lymphocyte and leukocyte levels, glomerular filtration rate and doses of immunosuppressive medications) were used to identify the presence of immunosuppression by comparing them with the TTV viral load. The gene discussed is CD4; the disease is graft versus host disease.