Lymphoproliferative responses to CMV antigen (left panel) and to PHA (right panel) in CMV seropositive autograft recipients. Eleven patients were evaluated before transplantation and 15 patients were assessed during the first 3 months after transplantation. The stimulation index was calculated as described in the Patients and Methods. A stimulation index ≥4.0 was considered positive. The median is indicated by the horizontal bar.