Development of antibodies reactive in antibody-dependent cellular cytotoxicity in infectious mononucleosis.

Serial sera from patients with infectious mononucleosis were examined for the emergence of antibodies reactive in antibody-dependent cellular cytotoxicity tests, using Epstein-Barr virus-superinfected Raji cells as targets. For this specific purpose, the antibody-dependent cellular cytotoxicity test proved to be of limited sensitivity because only relatively high serum dilutions can be tested dependably, due to prozone effects at low serum concentrations, and because antibody-dependent cellular cytotoxicity reactions at the 5% level are not always statistically significant. Under the conditions of the test, antibody-dependent cellular cytotoxicity-reactive antibodies were not measurable, or only barely measurable, in early-acute-phase sera, but they became detectable during convalescence and increased thereafter, gradually over many months to the range of titers seen in healthy persons after long-past-primary Epstein-Barr virus infections. The percentages of antibody-dependent cellular cytotoxicity ultimately attained were on the order of 20% in most patients and healthy individuals, but in others did not exceed 10%. The likely identity of the antibodies reactive in the test with antibodies to late Epstein-Barr virus-determined cell membrane antigens has been discussed.