Induction of plaque-forming cells in human blood lymphocytes cultured in the presence of antigen and Epstein-Barr virus: a study with normal donors and infectious mononucleosis patients.

Normal human peripheral blood lymphocytes, stimulated in vitro with SRBC in the presence of Epstein-Barr virus (EBV), gave rise to plaque-forming cells (PFC) specific for the antigen. PFC levels were very low before day 4 and increased thereafter, reaching a maximum around day 8. However, the kinetics of the response varied considerably from donor to donor and from experiment to experiment. In some instances a second peak of PFC was obtained beyond day 10. Large differences in the magnitude of the response were observed among different normal donors, the overall responsiveness range covering four orders of magnitude. Peripheral blood lymphocytes from infectious mononucleosis patients in the acute stage of the disease, when a high titre of heterophil and anti-EBV antibodies were present, did not give rise to PFC. A return to normal responses was observed during recovery from the disease.