Polyclonal Immunoglobulin Secretion by Human B Lymphocytes Exposed to Epstein-Barr Virus in Vitro

Epstein-Barr virus (EBV)-induced activation of human peripheral blood lymphocytes was studied by the use of a reverse hemolytic plaque assay (RHPA) for the detection of immunoglobulin-producing cells. The results were compared with the effects of pokeweed mitogen (PWM) on the same cell population. Both agents caused the development of immunoglobulin-producing cells in cultures of unseparated mononuclear cells. However, B cell populations sufficiently depleted of T cells by a variety of techniques to be unresponsive to PWM showed a marked response to EBV. The reactivity of B cells to PWM could be restored by irradiated T cells, whereas there was no effect of irradiated T cells on reactivity to EBV. These data suggest that the response to EBV in contrast to the PWM response is T cell independent. Lymphocytes secreting each class of immunoglobulin (IgG, IgA, and IgM) were found in EBV-stimulated cultures of both unseparated mononuclear cells and T cell-depleted cultures, demonstrating that the response in each immunoglobulin class is also T cell independent in this system. When unseparated cell populations and B cell populations cultured at the same cell concentration were compared, the latter showed a 2- to 5-fold increased reactivity to EBV. This difference appeared to be caused primarily by an enrichment of B cells as was suggested by experiments in which the two cell populations were compared at different cell concentrations.