Antibody-dependent autologous lymphocyte cytotoxicity against cells freshly transformed by Epstein-Barr virus.

Cytotoxicity against lymphocytes freshly transformed by EBV was studied in an autologous system by trypan blue exclusion of EBNA-positive cells and 51Cr-release assay. When EBV-tranformed lymphocytes were incubated with EBV-positive serum and autologous unfractionated lymphocytes or K-cells from sero-positive healthy donors, the transformed cells were significantly damaged. The cytotoxicity against newly produced EBNA-positive lymphocytes was also remarkable when sero-positive healthy donor lymphocytes were exposed to EBV, immediately followed by incubation with positive serum. In contrast, EBV-transformed cells incubated with autologous lymphocytes or T-cells alone were not significantly affected. EBV-positive serum alone was also not cytotoxic, regardless of inactivation. These results strongly suggest that antibody-dependent cellular cytotoxicity (ADCC) plays an important role in immunological defence against EBV oncogenesis in healthy humans. However, ADCC was not seen when immunosuppressed patients were examined.