Abstract
The experiments show that the phenomenon of regression, seen exclusively in Epstein‐Barr (EB) virus‐infected cultures of mononuclear cells from EB virus antibody‐positive donors, is mediated by cytotoxic T cells reactivated in vitro and specifically recognizing an EB virus‐induced lymphocyte‐detected membrane antigen LYDMA. Thus, effector T cells from regressing cultures kill autologous EB virus‐transformed cells but not autologous pokeweed mitogen‐stimulated lymphoblasts nor any of a range of EB virus genome‐negative human hemopoietic cell lines (K562, HSB2, BJAB, EB4) particularly sensitive to nonspecific natural killer‐like activities. Moreover, these reactivated effector cells exhibit classical HLA restriction of target cell recognition; in a survey of 14 effector cell donors, preferential lysis of the autologous virus‐transformed line was a consistent feature, while the relative degree of lysis of allogeneic lines was in general directly related to the number of HLA‐A and B antigens shared between effector and target cells. The pattern of reactivity shown by effector T cell preparations from any one donor was strikingly reproducible, and the results from a number of donors revealed differences between particular HLA‐A and B antigens with respect to the level of EB virus‐specific killing which was associated with sharing through these determinants.