Generation of Epstein-Barr virus antigen-specific suppressor T cells in vitro

Immunosuppression is a commonly observed phenomenon in Epstein-Barr virus (EBV)-associated disorders and malignancies. The purpose of this study was to determine whether EBV antigens could generate suppressor cell activity in vitro. Peripheral blood lymphocytes (PBL) were first treated with various concentrations of EBV antigens or culture medium for 5 days and then with mitomycin C. The cells were then washed and tested for their ability to abrogate the blastogenic response of fresh, autologous PBL to previously determined optimal concentrations of EBV antigens. It was found that excess of both EBV antigens tested (soluble antigen and virus particles) induced suppressor cells, while optimal antigen concentrations failed to do so. In addition, PBL incubated with excess of EBV antigens for 10 days, without mitomycin treatment, inhibited the response of fresh autologous lymphocytes to EBV antigens. The generated suppressor cells were found to be antigen-specific since they inhibited the response of sensitized lymphocytes to the inducing antigen only. Moreover, experiments performed using purified lymphocyte subpopulations indicated that the suppressor activity was associated with T-cell populations. Using T-cells specific monoclonal antibodies, we further determined that the inhibitory activity was due to suppressor (OKT 8+) T-lymphocytes; treatment of T-lymphocyte populations (exhibiting suppressor activity) with OKT 8 antibody and complement abrogated the inhibitory effect of these populations on the response of sensitized lymphocytes to EBV antigens. Taken together, these observations suggest that similar suppressor cells may be at least partly responsible for the immunosuppression observed in patients with an antigenic overload, particularly during persistently active virus infection or malignancy.