Autologous EBV-transformed B-LCL were used as target cells for the influenza virus-specific CTL assays. Equal volumes of target and effector cells were added to tissue culture plates, and 1:2 serial dilutions of effectors were made. After a 4-h incubation of the effector cells with the target cells, supernatants were collected and counted with the LKB 1272 Clinigamma counter. Percent specific killing was determined with the following equation: (experimental 51Cr release - spontaneous 51Cr release)/(maximum 51Cr release - spontaneous 51Cr release) x 100.